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Title: Deficiency and Delinquency - An Interpretation of Mental Testing
Author: Miner, James Burt
Language: English
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Educational Psychology Monographs

This volume, which is No. 21 in the Series, was
edited by J. Carleton Bell


An Interpretation of Mental Testing



Associate Professor of Applied Psychology, Carnegie Institute of
Technology, Pittsburgh; sometime lecturer at the school for teachers of
special classes, Minnesota State School for the Feeble-Minded

Warwick & York, Inc.

Copyright, 1918
Warwick & York, Inc.

                       DEFICIENCY AND DELINQUENCY

                           TABLE OF CONTENTS

 Preface                                                               1

 Chapter I. INTRODUCTION                                               3


 Chapter II. THE FUNCTIONS OF A SCALE IN DIAGNOSIS                    10

      A. THE MEANING OF INTELLECTUAL DEFICIENCY                       10




      A. THE DEFINITION                                               20


           (a) Deficiency is a Difference in Degree not in Kind       21

           (b) As to the Variation in the Frequency of Deficiency at  23
             Different Ages

           (c) As to the Number of Deficients not Detected by Tests   34

           (d) Allowance May be Made for Variability                  40

 Chapter IV. WHAT PERCENTAGE IS FEEBLE-MINDED                         47

      A. KINDS OF SOCIAL CARE CONTEMPLATED                            47




      E. COMPARISON WITH IMPORTANT ESTIMATES                          56



      A. THE BORDER REGION FOR THE MATURE                             82

           (a) Indication from a Random Group                         82

           (b) The Present Tendency Among Examiners                   95

      B. THE BORDER REGION FOR THE IMMATURE                          104

           (a) For the Binet 1908 Scale                              104

           (b) Data for Other Developmental Scales                   110

           (c) The Change in Interpreting the Borderline for the     116

 Chapter VI. DELINQUENTS TESTING DEFICIENT                           122



           (a) Women and Girl Delinquents in State Institutions      128

           (b) Women and Girl Delinquents in Country and City        134

           (c) Men and Boy Delinquents in State Institutions         141

           (d) Men and Boy Delinquents in County and City            148




      A. IN MINNEAPOLIS                                              177



      A. PRACTICAL USES OF THE SCHOOL TEST                           190

           (a) Estimating the Frequency of Deficiency by School      190

           (b) School Retardation as a Warning of the Need for       194

           (c) School Success as a Check on the Binet Diagnosis      197



 Chapter XI. DEFICIENCY AS A CAUSE OF DELINQUENCY                    210



      C. THE CAUSES OF DELINQUENCY                                   224

           (a) Constitutional Factors                                224

           (b) External Factors                                      225

           (c) Weighing Heredity Against Environment                 229

           (d) The Criminal Diathesis                                234

 Chapter XII. SUMMARY AND SUGGESTIONS                                239




           (a) Equivalent Units of Ability When the Distributions    254
             are Normal

           (b) The Year Unit of the Binet Scale                      260

           (c) Is Tested Capacity Distributed Normally?              267

           (d) Equivalent Units of Development When the Form of      275
             Distribution is Uncertain

      B. THE CURVES OF MENTAL DEVELOPMENT                            279

           (a) The Significance of Average Curves of Development     280

           (b) Changes in the Rate of Development                    290

           (c) The Question of Earlier Arrest of Deficient Children  294






 BIBLIOGRAPHY ON TESTED DELINQUENTS                                  324

   Other References Cited                                            329

 APPENDICES                                                          344

 INDEX                                                               353

                       LIST OF TABLES AND FIGURES


     I. Age distribution of deaths in the general population and of   30
          feeble-minded in institutions

    II. Mortality of institutional deficients in the United States    31
          compared with the general population

   III. Test borderlines with randomly selected Minneapolis           89

    IV. Results with the Binet tests for mental ages XI and XII       98
          (1908 series)

     V. Percentages of mentally retarded children as tested with the 106
          Binet 1908 Scale

    VI. Mental retardation of children as tested with the Binet 1911 111

   VII. Borderlines with the Point Scale                             115

  VIII. Test ages of the Glen Lake group of delinquent boys          124

    IX. Intellectual development relative to life-ages and school    125
          positions among the delinquent boys of Glen Lake

     X. Binet 1911 tests of boys consecutively admitted to the       151
          Detention Home at Thorn Hill, Allegheny County

    XI. Frequency of tested deficiency among over 9000 delinquents   159

   XII. Age and grade distribution of elementary school pupils in    178

  XIII. School retardation of Minneapolis delinquents and elementary 179
          school pupils

   XIV. Indices of frequency and amount of school retardation for    183
          Minneapolis delinquents and elementary school pupils

    XV. Percentage of pupils 12 and 13 years of age most seriously   193
          retarded in school

   XVI. School position of delinquents at Glen Lake relative to      204
          their intellectual development

  XVII. Goring's data as to the percentage of mental defectives      213
          among men convicted of various offenses

 XVIII. Goring's data as to groups of crimes committed most          214
          frequently by those mentally deficient

   XIX. Four-fold correlation table for juvenile delinquency and     222
          deficiency in Minneapolis

    XX. Average Intelligence Quotients of children of different      296

   XXI. Test records with random 15-year-olds                        344

  XXII. Test records with delinquents at the Glen Lake Farm School   349


     1. Mortality among feeble-minded in institutions compared with   32
          the general population

     2. School retardation of Minneapolis delinquents compared with  180
          elementary school boys

     3. Hypothetical development curves (normal distributions)       253

     4. The question of equivalence of year units                    265

     5. Hypothetical development curves (changing form of            277

     6. Tests of the development of memory processes. Medians at     285
          each age for the central tendencies of the tests

     7. Different types of development. Medians at each age for the  286
          central tendencies of the tests

     8. Forty tests of development. Distribution at each age for the 287
          central tendencies of the tests

     9. Relative positions at each age of the median and of          299
          corresponding bright and retarded children with the Form
          Board Test

                       DEFICIENCY AND DELINQUENCY


In undertaking in 1912 to examine the mental development of delinquents
for the clinic started and supported by the Juvenile Protective League
of Minneapolis, in connection with the Juvenile Court, I soon became
convinced that a safer method for evaluating the limit of
feeble-mindedness with tests was more needed than masses of new data.
The researches that have been published in the past three years do not
seem to have changed this situation. Numerous studies with psychological
tests are already available, but they generally treat of average rather
than borderline conditions. In the field of delinquency the work of
testing has been carried on with especial activity. Here, as well as
elsewhere, the conclusions seem likely to be misleading unless social
workers better appreciate the real place of mental tests, their value
and their limitations.

The tables of a few hundred juvenile delinquents and school children
examined in Minneapolis, which are presented in this book, indicate the
occasion rather than the aim of the present study. The purpose is mainly
to help clear the ground for other work with mental tests, and
especially to put the determination of feeble-mindedness by objective
examination with the Binet or other scales on what seems to me a sounder
basis. Furthermore, the results of objective testing which have been so
rapidly accumulating in the field of delinquency need to be assembled
and reorganized in order to avoid confusion. It is especially desirable
to discover a conservative basis for objective diagnosis of deficient
intellectual capacity in order to prevent very useful testing systems
from becoming unjustly discredited and to preserve the advance that has
been made.

The work out of which this monograph grew was begun through the
encouragement of Judge Edward F. Waite of the Hennepin County Juvenile
Court. His earnest co-operation and my interest in the field of mental
testing has led me to continue the study. Judge Waite's insight into his
court problems resulted in the early organization of a Juvenile Court
clinic (_153_, _170_) in Minneapolis. The clinic is in charge of Dr.
Harris Dana Newkirk, who has contributed materially to this study by his
thorough medical examination of each of the cases brought to him. To the
staff at the probation office I am also much indebted.

The earnest help of Superintendent D. C. MacKenzie, of the Glen Lake
Farm School for the juvenile delinquents of Hennepin County, made a
close study of our most interesting group of boys much more profitable
personally than I have shown here. For detailed expert work in
tabulation and in examinations I wish to express my thanks to my
advanced students, a half dozen of whom have contributed materially to
the data of this book.

                                                       JAMES BURT MINER.

 Carnegie Institute of Technology
     Pittsburgh, Pa.

                        CHAPTER I. INTRODUCTION

As an interpretation of the results which have been obtained with mental
tests, this book lies between the topics of deficiency and delinquency.
It is an attempt to discover the significance of objective measurements
of ability in connection with both of these fields. The pressing
practical problem was to find out what positions on a scale for testing
mental development were symptomatic of social deficiency. After working
out a percentage method for conservatively indicating these borderlines
for tested deficiency, it was then possible to reinterpret the test
records of over 9000 delinquents who have been examined with some form
of the well-known Binet Scale. The size of the problem of the deficient
delinquent has thus been determined on a significant scientific plan.
The outcome is a new basis for judging the current statements about this
problem by those who have used the Binet scale. Scores of investigators
by their tireless energy have provided data which may now be compared
for many types of delinquents and in many parts of the country. Some
sixty studies of deficient delinquents have been thus summarized from
the point of view of psychological tests.

Closely related to the problem of the frequency of feeble-mindedness
among delinquents is the question of the cause of delinquency. This has
further been considered in the light of the most important scientific
studies, especially those using the method of correlation. Among these
researches stands out the fundamental investigation of the causes of
criminality by Goring, a work which has received very inadequate
attention in this country, although it involved ten years study of a
group of 3000 convicts by the best quantitative methods. The careful
study of these objective investigations should take the question of the
relation of deficiency and delinquency out of the realm of opinion and
theory. It may be expected to have an important influence upon the
social handling of these problems. In this connection I have added a
chapter of suggestions which have grown out of my year's study of the
education of deficients and delinquents in European schools and

To determine the size of the problem of dealing with deficients,
especially deficient delinquents, is a task of first importance. In
spite of our more conservative basis for judging the results with tests,
the necessity of caring for the feeble-minded remains the most vital
problem connected with social welfare. The movement for more individual
training in our schools, which has been gaining such headway, may also
be encouraged by the evidence that maladjustment to school work is also
definitely related to delinquency.

It is essential that we should have objective data for determining the
borderline of tested deficiency among adults. To meet the present
serious lack of knowledge on this point, new data were collected which
for the first time afford the means of determining, by the use of a
randomly selected group what is a conservative borderline of tested
deficiency for those intellectually mature. These data include the Binet
test records for all the 15-year-old children who resided in seven
school districts in Minneapolis and who had not graduated from the
eighth grade.

The urgency of plans for indefinitely segregating certain types of the
feeble-minded, especially deficient delinquents, has placed a new
emphasis on those quantitative aids to diagnosis. The difficulty of
establishing feeble-mindedness before a court has been called to
attention by both Supt. C. A. Rogers (_173_)[1] of the Minnesota School
for Feeble-Minded, and Supt. Walter E. Fernald (_104_) of the
Massachusetts School. Both of these men recognize that psychological
tests are the most hopeful way of improving this situation.

A fundamental feature of the diagnosis of deficiency is the plan here
advocated for designating the borderlines on a scale on the basis of a
percentage definition of tested deficiency. This involves the
distinction of intellectual deficiency from certain rare volitional
forms of feeble-mindedness, which the tests do not at present detect.
This percentage definition seems to afford the best approach to a test
diagnosis. It is apparent that the data are insufficient for finally
establishing such a quantitative description of the lower limit for
passable intellects on a mental scale. The plan, however, may be easily
adjusted to new data, and meanwhile avoids some of the serious current
misinterpretations of test results.

While the idea of a quantitative definition of the borderline of
deficiency is not new, the percentage method seems to have certain
fundamental advantages over either the “intelligence quotient” of Stern
(_188_), the “intelligence coefficient” of Yerkes (_226_), or the
description in terms of deviation, mentioned by Norsworthy (_159_) and
Pearson (_164_, _166_, _167_). Several investigators, including Terman
(_57_) and Yerkes (_226_), are utilizing the percentage method
indirectly for describing the borderline of feeble-mindedness, but have
inadequately distinguished it from the ratios. While ratio and deviation
methods are possibly more serviceable for certain purposes, they are
especially faulty near the borderline of deficiency, since they are
affected by variations in the units of measurement and in the form of
distribution from age to age. My paper on a percentage definition and
the detailed plan for determining the borderline in the Binet scale,
which was read at the meeting of the American Psychological Association
in 1915, seems to have been contemporaneous with a similar suggestion by
Pintner and Paterson (_44_). They, however, would restrict the term
“feeble-mindedness” to tested deficiency, while I advocate the use of
percentage borderlines on a test scale as symptomatic of one form of
feeble-mindedness, much as excess of normal temperature on a clinical
thermometer is symptomatic of disease.

Although no system of objective tests will ever dispense with the need
for expert interpretation in diagnosing individual cases, still there
are few who would doubt that it is desirable to reduce the option of
expert judgment as much as we reasonably can. This is the scientific
method of procedure. The borderline cases, however, which are often most
troublesome in their delinquencies, are just those which will longest
defy rigid rules. The diagnostician who wants to be as free as possible
from external restraint will find in this border field of mental
capacity a happy hunting ground. His scientific instincts should make
him eager to discover when he leaves the mundane sphere and sallies
forth into uncharted realms where he bears the full responsibility of
his own opinion. Let me hasten to add that reasoning from objective data
in the mass to the diagnosis of an individual case may lead to serious
mistakes, unless one keeps alert to detect the exception from the
general rule, and unless one understands the numerous sources of error
entering into an examination. On the other hand the test results when
properly interpreted afford the most important criteria on which to base
a prognosis if they are considered in relation to the history of the
case and the medical examination.

By the use of more conservative borderlines for raising the presumption
of deficiency and also by designating a doubtful position on the scale,
on the plan advocated herein, it is possible to make scales for testing
mental capacity more serviceable both to the clinician and to the
amateur tester. The latter may use the scales for his own information or
may wish to discover whether an examination by an expert in mental
development is desirable, without attempting to make a diagnosis
himself. The scale may thus take a place in the study of child mentality
analogous to the familiar Snellen chart in the testing of vision. For
every teacher familiarity with a development scale may thus become as
essential and desirable as the knowledge of the chart for eye testing.
It should find a place in all progressive schools which do not have the
services of a clinician.

The Binet system of tests was used for obtaining new data on groups of
juvenile delinquents in Minneapolis and Pittsburgh. The use of this
scale, around which the discussion centers, grew out of the necessity
for immediate practical results for the clinic at the Minneapolis
Juvenile Court which I was called upon to serve. In 1912, when that work
began, there was practically nothing approaching norms with children for
any other scale of tests. Even today it is plain that there is more data
available for interpreting results with the Binet scale than with any
other system of tests. While my experience would make me unwilling to
advocate the Binet tests as an ideal method for building up a measuring
scale, I still feel that it remains the most useful method at present
for discovering the fundamental symptoms of intellectual deficiency. The
percentage method, here advocated, as the best way available for
determining the borderlines with a scale, would be quite as serviceable,
however, with any other testing system. It has been my aim to contribute
to the interpretation of the results of the tests as they are, not to
perfecting the arrangement or details of the separate tests.[2] It
happens that one of the main objections which has been raised to the
Binet scale, the inadequacy of its tests for the older ages, loses its
force so far as the _diagnosis of feeble-mindedness_ is concerned for
those who accept the borderlines described in this paper.

Some diagnosticians may hesitate to use the Binet scale because of the
criticisms it has received. Yerkes and Bridges state: “Indeed, we feel
bound to say that the Binet scale has proved worse than useless in a
very large number of cases” (_226_, p. 94). So far as this objection
arises from the attempt to use the descriptions of the borderline of
feeble-mindedness published with Binet scales, it will meet with a wide
response. The difficulty is hardly less, as I shall show, with other
scales. The definition of the borderline is certainly the vital point
with any objective method for aiding diagnosis. Only by improving
methods for determining the borderline can this weakness be attacked.
The central contribution of this paper is directed, therefore, to this
problem of the interpretation of the borderline, so that objective
scales may be made more reliable for purposes of diagnosis.

In Part Two I have added an intensive discussion of the measurement of
development and a comparison of the different objective methods for
describing the borderline. This may well be omitted by those who are not
interested in the technical aspects of these questions. To those who
care only for accounts of individual lives, let me say that I am
contributing nothing herein to that important field which has been
covered in authoritative form by Dr. Healy (_27_) and by Dr. Goddard
(_112_). They will find instead, I hope, the fascination of figures, a
picture book in which probability curves take the place of photographs
and biographies, in which general tendencies are evaluated and attention
is focussed upon the problem of properly diagnosing deficiency and upon
plans for the care of the feeble-minded, whether they be potential or
actual delinquents.


Footnote 1:

  Numbers in parenthesis indicate the references in the bibliography at
  the close of the book.

Footnote 2:

  Those concerned with other features of the Binet scale will find an
  admirable bibliography by Samuel C. Kohs, Journal of Educational
  Psychology, April, May and June, 1914, and September, October,
  November, and December, 1917. Other references are contained in the
  Bibliography by L. W. Crafts (_9_).

                                PART ONE
                        PRACTICAL CONSIDERATIONS



Whatever form the definition of feeble-mindedness may take, in this
country at least[3] the concept has become quite firmly established as
describing the condition of those who require social guardianship,
because, with training, they do not develop enough mentally to live an
independent life in society. The feeble-minded are socially deficient
because of a failure to develop mentally. They are proper wards of the
state because of this mental deficiency. Goddard says, they are
“incapable of functioning properly in our highly organized society”
(_112_, p. 6). The most generally quoted verbal description of the upper
line of social unfitness is that of the British Royal Commission on
Feeble-Mindedness: “Persons who may be capable of earning a living under
favorable circumstances, but are incapable from mental defect existing
from birth or from an early age (a) of competing on equal terms with
their normal fellows; or (b) of managing themselves and their affairs
with ordinary prudence.” It is clear that the intention is to
distinguish mental deficiency from senile dementia, from hysteria and
from insanity, in which there is a temporary or permanent loss of mental
ability rather than a failure to develop. Feeble-mindedness may,
however, arise from epilepsy or from other diseases or accidents in
early life as well as from an inherent incapacity for development.
Moreover, _mental_ deficiency, or feeble-mindedness, (I use the terms
interchangeably) does not imply that the social unfitness is always
caused by intellectual deficiency. Mind is a broader term than
intellect, as we shall note in the next section.

This definition of the feeble-minded is the main idea expressed by
Witmer (_221_), Tredgold (_204_), Pearson (_164_), and Murdock (_164_).
The historical development of the concept is traced by Rogers (_172_)
and Norsworthy (_159_). It is criticized by Kuhlmann (_140_) as
impractical and indefinite. The indefiniteness is indicated by such
terms as “under favorable circumstances,” “on equal terms,” and “with
ordinary prudence.” This objectionable uncertainty as to social fitness
can be considerably relieved for those types of feeble-mindedness which
involve the inability to pass mental tests, since this result can later
be correlated with subsequent social failure and predictions made during
childhood on the basis of the tests. Attempts to make the concept of
feeble-mindedness more definite have, therefore, naturally taken some
quantitative form in relation to objective tests. Binet and the French
commission in 1907 (_77_) called attention to the method in use in
Belgium for predicting unfitness objectively on the basis of the amount
of retardation in school at different ages. With the appearance in 1908
of the Binet-Simon revised scale for measuring mental development,
quantitative descriptions began to be concerned with the borderlines of
mental deficiency on scales of tests.

While the quantitative descriptions of tested deficiency do not include
all forms of feeble-mindedness, as I shall show in the next section,
they have made the diagnosis of the majority of cases much more
definite. Nobody would think of returning to the days when the principal
objective criteria were signs of Cretinism, Mongolianism, hydrocephalus,
microcephalus, epilepsy, meningitis, etc., which LaPage (_141_) has
shown are not found among more than 9% of 784 children in the Manchester
special schools. The impossibility of agreeing upon subjective estimates
of mental capacity without the use of objective criteria is well shown
by Binet's methodical comparison of the admission certificates filled
out within a few days of each other by the alienists for the
institutions of Sainte-Anne, Bicêtre, the Salpêtreire and Vaucluse.
These physicians gave their judgments as to whether a case was an idiot,
imbecile or higher grade. Binet says: “We have compared several hundreds
of these certificates, and we think we may say without exaggeration that
they looked as if they had been drawn by chance out of a sack” (_77_, p.

The rapid accumulation of data with psychological tests has made it
possible to take our first halting steps in the direction of greater
definiteness in diagnosis by a larger use of objective methods. This
increase in significance of the concept of deficiency is fruitful at
once in estimating the size of the social problem and planning means for
undertaking the care of these unfortunates. We can discover something of
the error in the previous subjective estimates of the frequency of
feeble-mindedness. We can bring together and compare the work of
different investigators, not only in our country, but throughout the
world. We can discover, for example, how important the problem of
deficiency is among different groups of delinquents, knowing that the
differences are not to be explained by differences in expert opinion.
Furthermore, we can now determine, with considerable accuracy, whether
the diagnosis made by a reliable examiner is independent of his personal

If we disregard the natural antipathy of many people to anything which
tends to limit the charming vagueness of their mental outlook, we may
endeavor to chart this horizon of tested deficiency with something of
the definiteness of figures, which shall at the same time indicate a
range of error. As soon as our aim comes to be to plot the borderline on
a measuring scale of mental ability, we find that the borderline must be
so stated that we can deal with either adults or children. Two sorts of
limiting regions must be described, one for mature minds and one for
immature minds. The latter will be in the nature of a prediction as to
what sort of ability the children will show when they grow up. We must
keep in mind, therefore, that we should attempt our quantitative
definition for both growing and adult minds. As soon as the growing mind
passes the lower limit for the mature it is then guaranteed access to
the social seas although it may never swim far from shore nor develop
further with advancing years. In seeking greater definiteness, our aim
should then be to describe both the limit for the mature individuals and
the limit for the immature of each age. In this paper the definition
will be restricted to _intellectual deficiency_, _i. e._, tested
deficiency. It will take the form of describing _the positions on a
scale below which fall the same lowest percentage of intellects_. This
percentage definition of intellectual deficiency offers such a simple
method of consistently describing the borderlines for mature and
immature that it is surprising so little attempt has previously been
made to work it out for a system of tests. Although the principle on
which the definition is based depends upon the distribution curve of
ability, it is concerned only with the lower limit of the distribution.
Since the exact form of this distribution is uncertain I have preferred
to call it a percentage definition of intellectual deficiency rather
than to state the limits in terms of the variability of ability.
Moreover the lowest X per cent. in mental development requires no
further explanation to be understood by the layman.


The first broad conclusion that impresses those who try to use mental
scales for diagnosing feeble-mindedness is that the lower types, the
idiots and imbeciles, can be detected with great accuracy by an hour's
testing. The difficulties pile up as soon as the individual rises above
the imbecile group. The practical experience of those in institutions
for the feeble-minded here becomes of fundamental importance. They are
able to supply the history of exceptions that should make us cautious
about our general rules. Certain people whom they have known for years
to be unable to adjust themselves socially because their minds have not
reached the level of social fitness will yet be able to pass
considerably beyond the lower test limit for mature minds. The mental
scales can only detect those feeble-minded who cannot succeed with our
present tests. This is the basal principle in using any system of tests.

Stated in another way, this first caution for anybody seeking the
assistance of a mental scale is that tests may detect a feeble-minded
person, but when a person passes them it does not guarantee social
fitness. The negative conclusion, “this person is not feeble-minded,”
can not be drawn from tests alone. Mental tests at present are positive
and not negative scales. This fact will probably always make the
expert's judgment essential before the discharge of a suspected case of
mental deficiency. When a subject falls below a conservative limit for
tested ability a trained psychologist who is familiar with the sources
of error in giving tests, even without experience with the
feeble-minded, should be able to say that this person at present shows
as deficient development as the feeble-minded. To conclude however that
any subject has a passable mind requires in addition practical
experience with feeble-minded people who pass the tests. It is very much
easier to state that the tests do not detect all forms of
feeble-mindedness than it is to give any adequate description of the
sort of feeble-mindedness which they do not as yet detect.

This distinction between the feeble-minded who do well with test scales
and those who do not, is well known in the institutions for the
feeble-minded. Binet sought to distinguish some of the feeble-minded who
escaped the tests by calling them “unstable,” or “ill-balanced,”
individuals as Drummond (_77_) translates the term. To use the
historical distinctions of psychology, their minds seem to be
undeveloped more on their volitional and emotional sides than on their
intellectual side. Weidensall (_59_) has described another type as
“inert.” She found that quite a number of the reformatory women might
slide through the tests but fail socially from the fact that “their
lives and minds are so constituted that they feel no need to learn the
things any child ought to know, though they can and do learn when we
teach them.” Again, it seems to be a disturbance of will through the
feeling, rather than an intellectual deficiency. Many of the so-called
“moral imbeciles” are probably able to pass intellectual tests lasting
but a few minutes. Like the unstable or inert they are not failures
because of a lack of intellectual understanding of right and wrong, but
because of excess or deficiency of their instinctive tendencies
especially in the emotional sphere. Such weakness of will may arise
either from abnormality of specific instinctive impulses or inability to
organize these impulses so that one impulse may be utilized to
supplement or inhibit another. We may call all this group of cases
socially deficient because of a weakness in the volitional, or conative,
aspect of mind.

The discrimination of mental activities which are predominately
emotional and conative from those in which intellect is mainly
emphasized is also well recognized by those who have been making broad
studies of tests in other fields than that of feeble-mindedness. Hart
and Spearman (_123_), for example, call attention to the fact that tests
passed under the stimulus of test conditions represent what the subject
does when keyed up to it rather than what he would do under social
conditions. We cannot be sure that speed ability as tested will
represent speed _preferences_. The subject may be able to work rapidly
for a few minutes, but in life consistently prefer to work deliberately.
Regarding the eighteen tests which they studied with normal and abnormal
adults they say: “These tests have been arranged so as to be confined to
purely intellectual factors. But in ordinary life, this simplicity is of
rare occurrence. For the most part, what we think and believe is
dominated by what we feel and want.” Kelley (_130_) finds by the
regression equation that the factor of effort amounts to two-thirds of
the weight of that of the intellectual factor in predicting scholarship
from teachers' estimates. Webb (_217_) thinks that he finds by tests a
general conative factor comparable to Spearman's general intellective

With the change in point of view that has come from the adoption of the
biological conception of the mind the discrimination of the different
forms of feeble-mindedness must be recognized as a distinction in the
emphasis on intellectual, emotional and conative processes, not a
distinction between actually separable forms of mental activity. On
account of the organic nature of the mind it is well established that
various mental processes are mutually dependent. Any disturbance of the
emotional processes will tend to affect the thinking and vice versa.
Even if we believe that emotions are complex facts, involving vague
sensations as well as feelings, and that terms like emotion, memory,
reasoning and will are names for classes of mental facts rather than for
mental powers, it still remains important to distinguish between
feeling, intellect and will, as well as to recognize the interdependence
of the mental processes. Common sense seems to agree with psychological
descriptions in regarding mind as a broader term than intellect, and
feeble-mindedness as a broader term than intellectual feebleness.

Since tests at present tend to reach the intellectual processes more
surely than the emotional, we describe those who fail in them as
intellectually deficient. The term “intellect” seems to be better than
“intelligence” because the latter seems to include information as well
as capacity, while the aim of measuring scales has been to eliminate the
influence of increasing information with age. To be thoroughly
objective, of course, one should talk about “feebleness in tested
abilities;” but we would then fail to point out the important fact about
our present scales that they detect mainly intellectual deficiency, that
they do not reach those forms of feeble-mindedness in which the weakness
in such traits as stability, ambition, perseverance, self-control, etc.,
is not great enough to interfere with the brief intellectual processes
necessary for passing tests. Intellectual deficiency will be used
hereafter to refer to those social deficients whose feebleness is
disclosed by our present test scales.

In the opinion of Kuhlmann these cases of disturbed emotions and will
which shade off into different forms of insanity should not be classed
as feeble-minded at all, although he recognizes that they are commonly
placed in this group. He regards them as an intermediate class between
the feeble-minded and the insane. He says: “They readily fail in the
social test for feeble-mindedness and because of the absence of definite
symptoms of insanity are often classed as feeble-minded. In the opinion
of the present writer they should not be so classed, because they
require a different kind of care and treatment, and have a different
kind of capacity for usefulness” (_140_). So long as this group of what
we shall term “conative cases” is discriminated from the intellectually
deficient it matters less whether they be regarded as a sub-group of the
feeble-minded or as a co-ordinate class. In grouping them with the
feeble-minded we have followed the customary classification. An estimate
of the size of this group will be considered later in Chapter III.


Conative forms of feeble-mindedness are perhaps the most serious types
in the field of delinquency. They are the troublesome portion of the
borderland group of deficient delinquents about which there is so much
concern. It is important to remember that it is just among these cases
that the test judgment is least certain. In this dilemma one principle
seems to be sound enough psychologically to be likely to meet with
acceptance. I should state this principle as follows: _A borderline case
which has also shown serious and repeated delinquency should be classed
as feeble-minded, the combination of doubtful intellect and repeated
delinquency making him socially unfit._ This will relieve the practical
situation temporarily until tests are perfected which will detect those
whose feebleness is specialized in those phases of volition centering
around the instinctive passions, control, balance, interest and
endurance. The principle recognizes that mental weakness is sometimes
emphasized in the volitional processes of the mind.

The principle is apparently in conflict with the rule advocated by Dr.
Wallin. Referring to the mental levels reached by individuals, he says:
“We cannot consider X-, XI-, or XII-year-old criminals as feeble-minded
because they happen to be criminals and refuse to consider X-, XI-, and
XII-year-old housewives, farmers, laborers and merchants as
feeble-minded simply because they are law abiding and successful”
(_214_, p. 707). At another place he insists “that the rule must work
both ways” (_215_, p. 74). Logically it would seem at first that it was
a poor rule which did not work both ways. Further consideration will
show, I believe, that there has been a confusion of feeble-mindedness
with tested deficiency. If all the feeble-minded tested deficient
intellectually then the tested level should determine whether or not
they were feeble-minded. This, however, is not a correct psychological
description of the facts. I prefer, therefore, to allow for those in a
defined narrow range of weak intellects to be classed as deficient
provided their weakness also manifests itself pronouncedly in the
conative sphere.

The principle that all mental deficients need not show the same low
degree of intellectual ability is clearly recognized in perhaps the most
important legal enactment on deficiency which has been passed in recent
years, the British Mental Deficiency Act of 1913. It states regarding
“moral imbeciles” that they are persons “who from an early age display
some permanent mental defect coupled with strong vicious or criminal
propensities on which punishment has had little or no deterrent effect.”
It specifically distinguishes them from the group of feeble-minded which
require guardianship because of inability to care for themselves.


Footnote 3:

  In Great Britain the term is restricted to those above the imbecile


                           A. THE DEFINITION.

In order to direct attention to the quantitative description of
intellectual deficiency which is here proposed, let us state the
percentage definition in its most general form. _Individuals whose
mental development tests in the lowest X per cent. of the population
are_ PRESUMABLY INTELLECTUALLY DEFICIENT, _unless their deficiency is
caused by removable handicaps_. Above these is a group of Y per cent.
within which the diagnosis of intellectual deficiency is uncertain on
the basis of our present tests. The size of the presumably deficient X
group is to be determined by the number of intellectually weak which
society is at present justified in indefinitely isolating. The
doubtfully deficient Y group should include all those who are so
intellectually deficient as to be expected to need assistance
indefinitely. _The feeble-minded, or_ MENTALLY DEFICIENT, _are those who
require social care indefinitely because of deficiency in mental
development_. They include the X group, that portion of the doubtful Y
group which is found to require isolation, guardianship or social
assistance, and any others not detected by the tests but requiring
prolonged social care on account of their failure to develop mentally.
Under the principle which we stated at the close of the last section the
combination of Y ability and persistent serious delinquency brings the
case within the group presumed to be feeble-minded.

Besides the greater definiteness and significance of such a definition
of intellectual deficiency, it affords the simplest practical criterion
for determining the borderline of passable intellects with a scale of
mental tests. A detailed comparison of the percentage plan with other
forms of quantitative definition will be found in Part Two. We may note
here, however, that it guards against a number of the absurdities of
current descriptions of the borderline with measuring scales. It is a
criterion which may be consistently applied to the borderline of both
the immature and the mature. It may be adapted with comparative ease to
any system of tests. It aids in comparing the frequency of intellectual
deficiency among different groups, for example, among different types of
delinquents, regardless of whether the investigators have used the same
series of tests, provided only that each series has been standardized
for similar random groups.

Any form of quantitative definition, on the other hand, involves certain
assumptions which must be defended before it can claim to be of
advantage for practical purposes.



Fortunately the tendency to describe the feeble-minded person as if he
were a different species from the normal has been definitely attacked by
two noteworthy researches, that of Norsworthy (_159_) and that of
Pearson and Jaederholm (_164_) (_167_). In these two investigations
mentally deficient children either in special classes or in institutions
have been compared with groups of normal children from the same
localities on the basis of objective tests. The results are uniformly
supported by numerous other studies of deficient and normal groups with
the Binet and other tests. The conclusion is, therefore, thoroughly
established that there is no break in the continuity of mental ability.
It grades off gradually from average ability, and continually fewer and
fewer individuals are to be found at each lower degree of ability. The
borderline of deficiency will, therefore, not be a mental condition
which clearly separates different kinds of ability, but a limiting
degree of capacity to be decided upon by social policy in attempting to
care for those who most need social guardianship. Since ability changes
gradually in degree it is necessary to indicate a doubtful border region
of degrees of ability on which expert judgment must supplement the test
diagnosis. Below the doubtful region the diagnosis is clearly supported
by objective test criteria, so that the only question to raise is
whether the condition is caused by removable handicaps. The percentage
definition thus strictly conforms to the best objective studies of
mental deficiency in treating deficiency as a difference in degree.

It should, perhaps, be said that this view is in direct conflict with
the opinion that mental deficiency is accounted for as a Mendelian
_simple unit_ character. The opposing view has been advocated by
Davenport (_95_, p. 310) and others in the publications of the Eugenics
Record Office, and accepted by Goddard (_112_, p. 556). It has been so
fully answered by Pearson (_164_) and Heron of the Galton Laboratory
(_127_) and by Thorndike (_198_) that there is no occasion to take up
the question in detail. We seem to be reaching an understanding so far
as our present problem is concerned. If the explanation of the
inheritance of mental ability is through Mendelian characters,
nevertheless intellectual ability is the result of such a complex
combination of units that it may best be thought of in connection with
the unimodal distribution of ability adopted in this study. No random
measurement of mental ability has ever shown any other form of

The attempt has also been made by Schmidt (_179_) to find qualitative
differences between normal and feeble-minded children by means of tests,
and by Louise and George Ordahl (_162_) to find qualitative differences
between levels of intelligence among feeble-minded children. While these
studies are very suggestive in pointing out the tests which most clearly
indicate differences between individuals, they seem to me to fall far
short of showing that the qualitative distinctions are anything more
than larger quantitative distinctions. It is not clear that the authors
intended them to mean anything more than this, so these studies do not
seem to conflict seriously with our assumption that intellectual ability
grades off gradually and uninterruptedly from medium ability to that of
the lowest idiot.


A quantitative definition of intellectual deficiency would certainly be
much simpler if it could be assumed that the percentage of deficients at
each age is practically constant during the time when a diagnosis of
deficiency is most important, say from 5 to 25 years. Otherwise the
objection might be raised that it is impracticable to determine
different percentages for each year of immaturity or to formulate our
borderlines of ability for a particular age. When the general
instinctive origin of intellectual deficiency is considered along with
the incurability of the condition, we seem to be theoretically justified
in assuming that the variation will be slight from one year of life to
the next. This assumption is tacitly made by all those who use Stern's
quantitative description of deficiency in terms of the mental quotient.
On the other hand, there is a feeling among some of the investigators
that there is a sudden influx of feeble-minded at particular ages and
this position should be examined. Probably more important than this
possibility of increase is the question of a decrease in frequency with
age on account of the excessive death rate among the deficients.

It is a natural supposition that there is a sudden increase in the
proportion of feeble-minded at adolescence. On account of the increased
rate of growth at this period we might expect to find greater
instability for a few years. It may well be that there is a rather
sudden influx of the unstable type of feeble-mindedness at this period.
Such an increase may occur without being detected by a series of brief
intellectual tests such as the Binet scale. It would be of the conative
type of feeble-mindedness that cannot at present be diagnosed by
objective tests, the type that requires diagnosis by expert opinion. It
is to be noted, however, that Binet, who paid much attention to the
unstable type, says: “Since the ill-balanced are so numerous at ten
years of age, and even at eight, we conclude that in many cases the
mental instability is not the result of the perturbation which precedes
puberty. This physiological explanation is not of such general
application as is sometimes supposed” (_77_, p. 18).

Only when an emotional disturbance is so great as to be detectable by
mental tests will this influx need to be taken into consideration in
stating the borderline for objective tests. The evidence that few cases
of feeble-mindedness are not detectable until after ten years of age is
all the other way. With the Stanford measuring scale, Terman and his
co-workers did not even find a noticeable increase in the variability of
the groups at the ages of adolescence (_57_, p. 555). It is to be
remembered also that we are not concerned here with mere instability
which corrects itself with more maturity, such as has been described by
Bronner among delinquents. This does not, of course, amount to an
incurable conative deficiency and is not classified under

Goddard has suggested that possibly the moral imbecile group comes into
our class of feeble-minded suddenly with a common arrest of development
at about the stage reached by the nine-year-old. He notes that “of the
twenty-three cases of this sort picked out for us (at Vineland) by the
head of the school department, fifteen are in the nine-year-old group,
five in the ten-year-old, two in the eleven, and one in the twelve”
(_113_). He regards this evidence, however, as meager and only
suggestive. Doll has given evidence of late appearance of retardation in
rare cases (_100_ and _99_).

It is to be noted that if a sudden change is found in the percentage of
children falling below a certain test standard it is perhaps more likely
to mean that there is a change in the difficulty of the tests at that
point. For example our Table V shows 1.3% of the nine-year-olds test two
or more years retarded, while 18.9% of the ten-year-olds are retarded
two years or more. This presumably indicates a change in the relative
difficulty of the tests for VII and VIII rather than a change in the
frequency of retardation at ages nine and ten. When we turn to Goddard's
norms for VII and VIII we find that 81% of the seven-year-old children
pass the norm for VII while only 56% of the eight-year-old children pass
the norm for VIII.

The Jaederholm data (_167_) obtained by applying the Binet tests to
pupils in the regular school classes and in special classes for the
retarded may suggest a possible influx of intellectual deficiency at
about 12 years of age or else “more mental stagnation in the
intellectually defective” at this life-age and after. If one were to
define intellectual deficiency in terms of the standard deviation of the
regular school children, this data suggests that there is a marked
increase in the number of children sent to the special classes at 12
years of age who are -4 S. D. or lower. Roughly speaking it amounts to
36 children at 12 years of age, 36 at 13, and 21 at 14, as compared with
11 at 11 years and 13 at 10 years. On the other hand, this may as well
mean that intellectual deficiency becomes greater in degree rather than
in frequency at these ages. The latter interpretation is adopted by
Pearson for the Jaederholm data, so that it is perhaps not necessary to
consider this evidence further. On the average the pupils in the special
classes fall about .3 S. D. months further behind regular school
children with each added year of life from 5 to 14 inclusive. A third
possible interpretation of the greater number showing the degree of
deficiency measured by -4 S. D. with the older ages should be mentioned.
It is possible that 1 S. D. has not the same significance for
5-year-olds as for 12-year-olds. The distribution of abilities at
succeeding ages may be progressively more and more skewed in the
direction of deficiency. We shall return to this point in Part Two as
showing the advantage of the percentage definition over a definition in
terms of the deviation. In connection with the Jaederholm data on
special classes one should also consider the fact that younger children
are not as likely to be detected by the teachers and sent to the special
classes. It is possible also that the difference in difficulty of the
tests for different age groups is somewhat obscured by using a year of
excess or deficiency as a constant unit as Pearson has in treating this
data. The bearing of this difference in difficulty was pointed out above
for Goddard's data.

The investigations by Pearson of children in the regular school classes
indicate that there is no important shift with maturity in the frequency
of those with different degrees of ability, when the ability is measured
either in terms of years of excess or deficiency with the Jaederholm
form of the Binet scale or in terms of estimates of ability relative to
children of the same age (_166_ and _167_). In both these studies the
correlation of ability with age was shown to be almost zero. For tested
ability for 261 school children “r” was .0105, P. E. .0417; with the
estimated ability, the correlation ratios were for 2389 boys, .054, P.
E. .014; for 2249 girls, .081, P. E. .014. Until we have better data
this is certainly the most authoritative quantitative answer to the
question of the shift with age in the frequency of the same relative
degree of mental capacity.

The best method of empirically settling this question of the early
appearance and constancy of deficiency would be to test the same group
of children again after they had reached maturity and find out how many
of those who tested in the lowest X per cent. still remained in the same
relative position. This is, of course, not possible at present, but it
certainly should be done before we are dogmatic as to the permanent
isolation of the lowest X percentage at any age. The nearest approach to
this sort of evidence is Goddard's three annual testings of a group of
346 feeble-minded children with the Binet scale (_117_, p. 121-131).
Among these 109 showed no variation, 123 gained or lost 0.1 or 0.2 year,
18 lost 0.3 or more, and only 96 gained 0.3 or more of a year. With so
small a change in absolute tested ability the probability of a change in
position relative to normal children seems to be slight. Only one of the
76 who had tested in the idiot group gained as much as a half year in
tested age in three years.

It is not possible to settle this question of the constancy of the
percentage of intellectual deficiency from one life-age to the next by
considering the frequency of different ages of children among those who
are sent to special classes for retarded pupils. This is evident from
the fact that these classes contain a considerable proportion of those
who are feeble mentally mainly because of conative disturbances. These
would not be detected by our present tests and would not be classed as
_intellectually deficient_. In the second place the pupils for the
special classes are usually selected mainly on the advice of their
teachers, who cannot, of course, without tests select those who are
intellectually deficient except by trying them for a number of years in
the regular school classes. This means that a smaller percentage of
pupils in the special classes at the younger ages is to be expected.

The figures of the U.S. Census as to the ages of inmates of the
institutions for feeble-minded are also of little significance in
connection with the question of the variation from age to age. That the
number of inmates at the different ages is affected most largely by the
pressure of necessity for shifting the care from their homes to the
institution is shown by the fact that three-fourths of the admissions
are of persons over 10 years of age. It is also indicated by the fact
that for the period from 15 to 19 the males are over 20% more frequent
than females, while from 30-34 the females are nearly 20% more frequent.
Considering those ages most frequently represented in the institutions,
10-24 years, the average variation for the three five-year periods in
the percentage of the population of the corresponding ages who are in
these institutions is only 0.01%. The middle five-year period has the
most, but even if there were a cumulation of feeble-mindedness with age,
which is not shown, we would anticipate a change of not more than 0.05%
for these 15 years. This would be clearly negligible in considering the
general problem.

That little allowance for the variation from age to age need be made for
the number of cases not discoverable at the beginning of school life is
further indicated by report of the Minnesota State School for
Feeble-Minded. It shows that in only 247 out of its 3040 admissions was
the mental deficiency known to commence after six years of age (_154_).
If the number of feeble-minded who should be isolated were found to
increase after school age less than one in 10,000 of the population, as
this suggests, it would surely be better to neglect this variation from
age to age than to emphasize it in dealing with the problem of objective
diagnosis and social welfare.

How rare is the onset of feeble-mindedness after five years of age is
also shown by the frequency of hereditary causes. In his study of the
300 families represented at Vineland, Goddard places only 19% in his
“accidental” group and 2.6% in the group for which the causes are
unassigned. The rest are either in the hereditary group, probably
hereditary, or with neurotic heredity. Half of the cases in the
“accidental” group are due to meningitis. His histories show that only 9
of the “accidental” and unassigned groups were unknown at 5 years of
age. This is only 3% of his total feeble-minded group. To these might be
added, perhaps, a few from the hereditary groups who did not show their
feeble-mindedness at so early an age, but so far as I can judge these
would not be of the intellectually deficient type that would be
detectable by the Binet scale at any age. They would test high enough
intellectually to pass socially and require expert diagnosis to be
classed as feeble-minded.

Certain diseases, epilepsy and meningitis, are undoubtedly causes of
feeble-mindedness. The evidence, however, seems to be that they are so
rare compared with the mass of mental deficiency that after 5 years they
may well be offset by the excessive death rate among the feeble-minded.
That recoveries from feeble-mindedness are insignificant is generally
agreed. Among the 20,000 in institutions in 1910 only 55 were returned
to the custody of themselves. This is further evidence of the
fundamental, if not congenital, nature of the deficiency.

While the evidence submitted above makes it seem fair to assume that the
increase in the frequency of a certain degree of intellectual deficiency
with age is probably negligible, it is not clear that the decrease with
age in the proportion of feeble-minded caused by an excessive death rate
may be neglected even for the test ages 5 to 25. By searching the
literature it has been possible to assemble the records for nearly 3500
deaths among the feeble-minded in institutions in this country and Great
Britain distributed by ages in ten-year periods. This evidence is
presented in Table I. The number of cases under five years of age living
in the institutions is so small that the deaths under five years are
certainly misleading. They have, therefore, been omitted from the table
and the distribution calculated for those five years or over (_123_,
_154_, _204_, _205_). Comparison is made with a similar distribution of
the total deaths for a period of five years from 1901 to 1904,
inclusive, within the area of the United States in which deaths are
registered, compiled from the special mortality report of the Bureau of
the Census (_206_). This registration area has a population of about
32,000,000. The general agreement of the distribution of deaths among
the four different groups of institutional inmates seems to make it
reasonable to assume that the United States group of institutional
deaths for the year 1910 is a conservative description of excessive
death frequency at the early ages among the feeble-minded in

 TABLE I. _Age Distribution of Deaths in the General Population and Among
                     Feeble-Minded in Institutions._

             │Population│                     Ages
             │          │ 5-14  │ 15-24 │ 25-34 │ 35-44 │ 45-54 │ 55 &
             │          │       │       │       │       │       │ over
 Gen'l—U. S. │ 1,897,492│ 6.1%  │ 9.6%  │ 12.8% │ 13.0% │ 13.6% │ 44.9%
 in death    │          │       │       │       │       │       │
 registration│          │       │       │       │       │       │
 area        │          │       │       │       │       │       │
 F. M. 1910  │       840│ 26.6  │ 33.0  │ 18.9  │  9.1  │ 45 &  │
 in          │          │       │       │       │       │ over  │
 Institut'ns │          │       │       │       │       │ 12.3  │
 in U. S.    │          │       │       │       │       │       │
 F. M.       │       997│ 34.3  │ 41.1  │ 10.4  │  6.5  │  3.5  │ 55 &
 British     │          │       │       │       │       │       │ over
 (Earlswood) │          │       │       │       │       │       │  4.2
 F. M.       │       613│ 34.7  │ 46.8  │  9.5  │       │ 35 &  │
 British     │          │       │       │       │       │ over  │
 (Barr)      │          │       │       │       │       │  9.0  │
 F. M.       │       982│ 27.6  │ 38.0  │ 16.1  │  8.6  │  3.5  │ 55 &
 Faribault   │          │       │       │       │       │       │ over
 Minnesota   │          │       │       │       │       │       │  6.2

  TABLE II. _Mortality of Institutional Deficients in the United States
 Compared with the General Population, Showing its Possible Effect on the
               Frequency of Deficiency at Different Ages._

                                │ 5  │ 10 │ 15 │ 20 │ 25 │ 30 │ 35 │ 40
 General population             │1000│983 │972 │956 │934 │903 │872 │835
 Deficients in Institut'ns      │1000│795 │696 │606 │503 │428 │349 │290
                                │    │    │    │    │    │    │    │
 Per cent. deficient if 1% at   │1.40│1.11│1.00│    │.75 │    │    │
   age 15                       │    │    │    │    │    │    │    │

[Illustration: FIG. 1. _Mortality among Feeble-Minded in Institutions
Compared With the General Population_]

A comparison of the death rates of the feeble-minded and the general
population at different ages is of prime importance in connection with
all attempts at quantitative descriptions of deficiency. Heretofore this
has been completely neglected. Fig. 1 and Table II have been prepared to
provide a roughly adequate estimate, on the basis of the above data for
the United States, as to the survival of 1000 institutional cases of
feeble-minded 5 years of age for successive age periods compared with
1000 people in the general population. In constructing this table it was
necessary to assume, since the facts were not given, that the age
distribution in the registration area of the general population was the
same as for the United States as a whole (census of 1910) and that the
number of feeble-minded in the institutions at the various age periods
was equal to the number enumerated on the first of January plus the
admissions during the year 1910, disregarding the number discharged
since they are not distributed by ages. The average annual death rate
among the institutional cases of feeble-minded 5 years of age and over
in the United States in 1910 was 35.19 per thousand, while the
corresponding death rate in the general population of the registration
area for the five years 1901-1904 inclusive was 13.56. Assuming that the
death rates are uniform within the five-year periods, the decline in the
proportion of institutional feeble-minded from 5-25 years of age as the
result of excessive mortality is indicated by the last line in Table II,
after allowing for the mortality in the general population. That this
effect of excessive mortality upon the percentage of feeble-minded
cannot be neglected between 5 and 25 years of age is apparent unless the
mortality among institutional cases is much greater than it is among the
deficient generally. As the figures stand the proportion of
feeble-minded would be reduced nearly one-half between ages 5 and 25.
Only a small part of this reduction probably would be compensated for by
new cases developing from accident or disease. On the other hand there
is little doubt that the institutions contain an excessive proportion of
low grade cases among whom the mortality is much greater. The mortality
among institutional cases is, therefore, probably not typical of that
among the feeble-minded generally. Nevertheless it is so great that any
quantitative definition of deficiency which neglects it entirely is open
to serious objection. We shall, therefore, keep this variation in mind
in connection with the discussion in the next chapter of the percentage
which is deficient, and in the adaptation of the definition to a
measuring scale. It is clear that the percentage should be so chosen as
to allow best for the possible large effect of excessive mortality among
the deficients. Finally, it should be said that the percentage
definition of feeble-mindedness might be modified to meet a varying
percentage from age to age should that ever become desirable.


If most of the feeble-minded for whom society should provide were of the
type which is only conative and not detectable by our present objective
tests, a quantitative definition would be abortive. We must, therefore,
study our assumption that it is worth while to direct our attention to
those who are intellectually deficient. We shall attempt to discover how
frequent are the primarily conative types.

Before examining the quantitative evidence we may note that it is in
conformity with two prominent recent tendencies in psychology to
subordinate specialized abilities, as compared with abilities which
function commonly in many situations. The first of these tendencies is
represented by the fundamental researches of Hart and Spearman (_123_)
(_185_). This is not the place to set forth the technical work on which
their conclusions are based. It may be said, however, that, with 17
different psychological tests, they were unable to discover any
important specific mental weakness which distinguished adults who were
suffering with any one of various mental abnormalities, including
imbecility, manic-depressive insanity, dementia praecox, paranoia, and
general paralysis of the insane. This may have been the fault of the
tests, but it seems to be more likely that the fault lies in the custom
of emphasizing special abilities and disabilities, at least from the
point of view of tested capacities. On the other hand, all of these
mental abnormalities showed a weakness in general intellectual ability.
This is true whether this general ability be regarded, as it is by Hart
and Spearman, as due to a general fund of brain energy, or whether
general ability be taken to refer to the common recurrence of many
specific abilities in much of our mental life. Its significance for this
study is that a series of varied tests, such as that of Binet, may be
expected to give a good estimate of general ability, and its failure to
disclose specific disabilities is thus less important.

The second influence in psychology tending to emphasize average tested
ability is the establishment of the biological conception of the mind
which recognizes the mutual interdependence of the mental processes,
organically united through the activity of the brain. So long as
intellectual, emotional and volitional processes are all mutually
dependent, a disturbance of one aspect of mental life is bound to affect
the others. In considering the mutual dependence of the mental
processes, it is important to weigh carefully the striking examples
which Bronner[4] has brought together, illustrating special abilities
and disabilities. She has made an admirable start toward a differential
diagnosis of special defects in number work, language ability and other
mental activities. The degree of special deficiency which results in
social failure could be placed upon an objective basis, but the rarity
of special deficiencies as compared with general deficiency will make
this a slow task. In the meantime we may rely upon the mutual dependence
of the organic processes as a point of view which emphasizes the common
spread of deficiency to many activities. Knowledge of a single case of
specific disability is sufficient to make us recognize that such cases
do occur. On account of the rarity of those cases and the absence of
objective criteria, it seems necessary to leave the further
differentiation to the future, considering here only those cases which
may be grouped together as conative, as contrasted with those detected
by our general intellectual tests.

Whether the group of primarily conative cases is of any considerable
size can be only very roughly estimated at present, since the diagnosis
of such cases of feeble-mindedness rests at present almost exclusively
on the subjective opinion of the examiner. Before their diagnosis is put
upon an objective basis we must have a different form of test directed
at such traits of will as initiative, perseverance, stability and
self-control. These probably center on the mental side around the
instinctive emotional background of interest and the passions, while, on
the physical side, they raise the question whether the subject's energy
is adequate to endure the strain of competition or whether it shows
itself only in sudden bursts.

If the diagnosis of conative cases could be determined objectively, it
is possible that most forms of social unfitness would be found highly
correlated with intellectual deficiency. On the other hand, when the
diagnosis of unfitness for school or social life depends merely upon the
opinion of experts or teachers, the inaccuracy of the diagnosis may show
a wide discrepancy between the so-called conative and intellectual types
of deficiency. Binet, on the basis of his acquaintance with the pupils
in special classes, suggested that the number of unstable children is
probably equal to the number of those who are intellectually unsuited
for the ordinary schools or institutions (_77_). Since he then places
the total number of the two classes at four or five per cent., it is
apparent that he is discussing a higher type of ability than is usually
included under the term feeble-minded. We can get somewhat better
evidence on this question by studying the results of Binet tests applied
to children cared for in special classes or in institutions for the
feeble-minded. Chotzen (90) presents a table of 280 children in the
_Hilfsschule_ in Breslau, only 201 of whom, however, he himself
diagnosed as feeble-minded, _i. e._, _debile_ or lower. Of these only 51
were intellectually deficient as indicated by the Binet tests when we
include the doubtful cases according to the criteria we have adopted in
this study. If we suppose that, in addition to those in the special
classes, there would be one intellectually deficient child in an
institution for feeble-minded for every child testing deficient, we
would then guess that only 40% of the feeble-minded children in Breslau
were intellectually deficient. This sort of estimate seems to agree with
Binet's belief that half of the children requiring special care, at
least during school ages, are cases which are primarily conative.

Pearson has approached the same problem in another way (_164_) (_167_).
He has used the results of the psychological tests applied by Norsworthy
to children in New York in special classes and institutions for
feeble-minded compared with those in the regular school classes, and the
results of Jaederholm obtained with the Binet tests applied to 301
children in Stockholm in the special classes compared with 261 others
selected from the regular classes. He found that “70.5% of normal
children fall into the range of intelligence of the so-called mentally
defective; and 60.5% of so-called mentally defective children have an
intelligence comparable with that of some normal children” (_167_, p.
23). On the statistical assumption that those in the normal classes
would distribute according to the Gaussian normal probability curve he
estimates that, with the Binet tests, among those in the special classes
“10% to 20%, or those from 4 to 4.5 years and beyond of mental defect,
could not be matched at all from 27,000 children” (_164_, p. 46).
Another 20 to 30% could be intellectually matched by those in the
regular classes having from 3 to 4.5 years of mental deficiency, but
they would be matched very rarely. On the assumption that 1% of the
children were feeble-minded, not more than about two children in a
thousand of this regular school population would be expected to be 3 or
more years retarded and thus overlap those of like deficiency in the
special classes (_167_, p. 30). Considering the results of Norsworthy's
study he says on similar assumptions: “It seems, therefore, that a
carefully planned psychological test, while not sufficing to
differentiate 50 to 60% of the mentally defective from the normal child,
would suffice to differentiate 40 to 50%” (_164_, p. 35). Again we come
back to the estimate that psychological tests may well be expected to
select nearly half of the children at present found in special classes
for retarded pupils. Moreover, a considerable part of the overlapping of
intellectual deficiency in the regular classes with that in the special
classes which he found may be accounted for by the inadequate methods of
selection of pupils for the special classes by teachers or examiners who
have used no objective tests. Some who were left in the regular classes
should undoubtedly have been transferred to special classes and vice
versa. There seems to be nothing to indicate that less than half of
those properly sent to special classes would be of clear or doubtful
intellectual deficiency. If the tests served to select even a smaller
proportion of those assigned to special instruction, the “school
inefficients” as Pearson calls them, their value as an aid to diagnosis
would be demonstrated.

Among groups of delinquents, where we would expect the purely conative
cases to be more common, we find that a careful diagnosis of
feeble-mindedness on the basis of test data, medical examination and
case history indicates that conative cases without serious intellectual
deficiency are much rarer than intellectually deficient delinquents. At
least this is the evidence of one study where such information is
available. Kohs at the Chicago House of Correction found among 219 cases
over 16 years of age, which he diagnosed as feeble-minded, only 28
tested XI and there were only 52 who did not test either presumably
deficient or uncertain intellectually according to our criterion.
Another bit of evidence is that collected at the Clearing House for
Mental Defectives in connection with the New York Post-Graduate School
of Medicine, where 200 consecutive cases (108 males) were examined by
Miss Hinckley. Her graphs show that only 15% tested X or above with the
Binet revised scale, _i. e._, above those presumably deficient in
intellect. The cases were from 13 to 42 years of age. The clearing house
provides an opportunity for social workers to have suspected deficients
examined and the few cases over X seems to indicate that the purely
conative type is not very commonly met with among the social workers.

When we turn to the institutions for the feeble-minded we find that they
are today caring for few solely conative cases. Although I can find no
tables which give both the life ages and mental ages of the individual
inmates, we can at least be sure that few test so high as X, or above
with the Binet scale. This means that only a few have as yet reached the
threshold for passable adult intellects, which should be attained by 15
years of age. At the Minnesota state institution for the feeble-minded
in Faribault among 1266 inmates, excluding epileptics, 41 tested X; 28,
XI; 12, XII; and 8, XIII, a total of 7% (_154_). At Vineland, N. J.,
Goddard reported among 382 inmates, 14 tested X; 5, XI; and 7, XII,
about 7%. Some of the children who were under 15 in life-age might later
develop above the limit for intellectual deficiency. Of the 1266 at the
Minnesota institution, however, 508 were 15 or over at the time of their
admission, so that at least 82% of the 508 were clearly intellectually
deficient. Eight per cent. more tested X and were in the doubtful group
in intellectual ability according to the criteria we have adopted. This
suggests that not more than about 10% of those who are at present
isolated in institutions are there for feebleness of will alone. It
seems to confirm our presumption that the intellectually deficient
discovered by tests form the great majority of the social deficients who
need prolonged care or assistance.


The quantitative definition of intellectual deficiency must be made with
careful allowance for irregularities among different mental processes,
among different individuals, and among different groups. Theoretically
it is possible to place the borderline so low that a case with that
degree of deficiency and without removable handicaps would be clearly
feeble-minded. The chance that the diagnosis would be mistaken could be
reduced to any minimum desired. Above this a wider region of doubtful
deficiency could then be stated in similar form. This is the plan that
we suggest in attempting the percentage definition. Practically,
however, the plan assumes that a suitable allowance can actually be made
for these variations and raises a number of problems as to variability
which should be considered. Four of these sources of variation are
discussed below: (1) the variation due to a limited sample of
individuals measured, (2) the variation among different communities, (3)
the variations arising from sex, race and social differences, (4) the
variation of the same individual from one mental process to another. We
do not have the problem of neglecting these variations, but of
adequately allowing for them both in the percentage of presumably
deficient and in the doubtful region.

(1) _Variation among Samples of Individuals Measured._ The error
introduced by the fact that measurements are made on a limited rather
than an unlimited number of individuals, in establishing the standards
with a system of tests, can be taken care of statistically fairly well
by applying the theory of probability as to the error of a percentage in
a single sample. The range of the error can then be indicated on the
measurement scale. This supposes, however, that each sample to be
measured is taken from a random group and not from a selected group.
Allowance for this error of sampling is therefore complicated by the
fact that the usual test data have been obtained from groups of _school
children_, even when there has been no further selection within the
school group. Data on school children are certainly reliable only within
the years of compulsory school attendance. Ordinarily in this country,
they are not reliable for children of 14 years of age or over. Moreover,
the point of the scale which is reached by the lowest X percentage of
school pupils will exclude a slightly larger percentage of all children
of corresponding ages, since the idiots and some imbeciles are not sent
to the ordinary schools. This slight discrepancy should be kept in mind.
The problem of avoiding selected samples among adults is still more
difficult; but we found that it was possible in one community at least
to measure all the 15-year-olds in the lowest X percentage in certain
districts, as we shall note later. By this age, mental processes are
probably very much like those of adults, except for the amount of
information and practise.

(2) _Variation among Different Communities._ Under any conception of
deficiency it is clear that there are relatively more deficients in some
communities than others. The percentage should, of course, not be
determined for a small community such as a city or county, but for a
state or a nation in order to avoid the difficulty of the difference
between communities. It would not interfere with the plan for isolating
the lowest X percentage of a state even if that meant isolating 10% in
one small community and none in another. Indeed, it might be expected to
do just that, when one considers the accumulation of deficiency in
certain settlements such as Key has shown (_131_, p. 63). The data on
which the borderline with a measuring scale would be established should,
of course, not be obtained from communities known to be unusual in
respect to the frequency of deficiency.

Since social failure is our final criterion for judging deficiency, we
must further consider that it is easier for a person to survive in one
environment than in another: in the country, for example, than in the
city. This sort of problem has led to considerable confusion. Goddard
remarks: “In consequence of this it happens that a man may be
intelligent in one environment and unintelligent in another. It is this
point which Binet has illustrated by saying 'A French peasant may be
normal in a rural community but feeble-minded in Paris.'” (_117_, p.
573.) Goddard then goes on to suppose that a delinquent with the
intelligence of a sixteen year old may be “defective” because he happens
“to have got into an environment that requires a twenty-year-old
intelligence.” The suggestion that a criminal might be excused on the
ground of deficiency because he happened to fall among bad companions is
a _reductio ad absurdum_. Clearly environment must be defined as
ordinary environment, available environment or by some similar concept,
or else the definition of deficiency loses all significance. In another
place Goddard more properly suggests that it would be well to “draw one
line at that point below which a person of that intelligence is not
desirable or useful _in any environment_” (_117_, p. 3).

So long as the care of the feeble-minded is a state problem the
percentage of passable intellects would apparently be determined for the
available environment in that state. The problem of social care cannot
mean that the state should care for college men because they cannot
survive among college men or in the station of life into which they may
have been born. So long as there are environments within the community
where they can survive it is a problem of shifting them in their social
habitat, not a problem for social care. The same is true for the low
grades of intellect. It is not likely, however, that any portion of the
community could absorb many more of the low degree intellects. For the
problem of social care for the feeble-minded, the question: What
environment will allow this individual to survive? becomes the question:
Can he survive in any available environment in his community? It would
seem very hazardous to suppose that the different opportunities for
survival afforded by different localities in a state would be large
enough to care for more than the group of doubtful cases which should be
allowed for in a quantitative description of the border region.

(3) _The Variation with Sex, Race, and Social Position_ has been
carefully called to attention by Yerkes and Bridges in their studies
with the Binet Point Scale (_225_, Chap. V and VI). It may very well be
that not as high ability should be expected of certain groups as of
others; as a matter of moral obligation, they are not as responsible for
their conduct or their attainments. On the other hand this does not
directly affect the question, what lowest percentage of intellects
cannot get along in society? When that percentage is determined for the
environment available in the community all those who fall within it
might even turn out to be of one sex or of one nationality or of one
social position, without affecting the question whether they should be
cared for by society, or what grade of intellect is not socially
passable? Temporary social handicaps, such as lack of familiarity with
the language, lack of training, etc., must, of course, be allowed for so
far as they affect the individual's test record. Whether the difference
of 5% to 10% in the score of pupils born to non-English-speaking
families compared to their companions' (_225_, p. 66) is due to the
temporary handicap of language or to a permanent difference is, however,
just the problem which the Yerkes and Bridges study does not answer. The
fact that the difference is even greater for older children suggests
that it may indicate an inborn difference between the groups compared.

A diagnosis of deficiency should not be made until the examiner is able
to estimate whether the removal of training or health handicaps would
bring the individual above the borderline. So far as known temporary
handicaps affect the standard of the test results with groups they
should, of course, also be taken into account. On the other hand, it is
clear that the borderline which predicts social failure should not be
shifted to allow for differences in permanent handicaps whether those be
of race, sex or social position.

(4) _The Variation among Different Mental Processes._ With our present
knowledge the most difficult variation for which we must make allowance
at the borderline is the variation from one trait or process to another
in the same individual. One phase of it was discussed above under “c.”
The investigation of Norsworthy throws light on this question.
Summarizing her tests she says: “Among idiots there is not an equal lack
of mental capacity in all directions. There is something of the same
lack of correlation among the traits measured in the case of idiots as
there is with ordinary people” (_159_, p. 68). Again: “The idiots are
nearest the central tendency for children in general in the measurements
of mental traits which are chiefly tests of maturity, and farther and
farther away as measurements are made which are tests of ability to deal
with abstract data. They are two and a half times as far from the median
for children in general in tests like the genus-species test as they are
in tests like the A test or the perception of weight.” Weidensall (_60_)
and Pyle (_46_) also compare delinquent and normal individuals for
different tests, showing a variation with the sort of mental activity

While Norsworthy thus presents evidence of certain specializations of
deficiency, she notes, however, that perhaps feeble-mindedness is more
typically general than specific and that general deficiency is more
important to consider than specific. Even with that test with which her
group of retarded and feeble-minded children did best, only 28% of them
passed the point which would be excelled by 75% of the children in
general. In their worst test only 1% passed this point. It is also to be
noticed that those tests in which they most nearly approached ordinary
children are for just those simple processes which would be least likely
to be of use in the struggle for social existence. As a whole,
therefore, there is nothing in her results which shows that any
appreciable number of children who were deficient in the average of
tested abilities, would have good enough special ability along a few
lines to make them socially passable. Indeed, for all that we know at
present, the borderline for _passable ability_ in each of our various
mental processes might vary quite as much as Norsworthy found, without
this variation affecting a prediction of failure based upon the average
of a series of tests.

On account of the great attention that has been paid to individual
differences in recent years, on account of their importance for
diagnosis, for determining the causes of deficiency, and for planning
for the training of deficients, we have come almost to the point where
we forget the significance of the average as the most common condition
with which we have to deal. The lack of complete correlation between
abilities of an individual does not make us hesitate to use the concept
of his average ability; it should not make us neglect or misunderstand
the significance of the position of an individual testing low down on
the scale. For the problem of social care the borderline position on a
scale is immensely more important than higher ability. It seems
advisable, therefore, to define this borderline ability with some
suitable allowance for variability in mental processes. It is far safer
to judge an individual's chance of survival by his average or general
tested ability than by the little knowledge that is as yet available
regarding special abilities.


Footnote 4:

  AUGUSTA F. BRONNER. _The Psychology of Special Abilities and
  Disabilities._ Boston, 1917, pp. vii, 269.



At first it seems like a hopeless task to try to bring harmony out of
the confused estimates of the proportion of the feeble-minded in modern
society. Authoritative estimates by commissions or by recognized experts
range from less than 0.2% to 5.0% that is, from 2 to 50 per thousand.
Further study of these estimates shows that they reflect not so much a
difference in expert opinion about the same problem as differences in
the problems which were considered in making the estimates. As soon as
we compare only those estimates that have been made to answer the
question, what percentage of low grade minds should be provided with a
certain form of social care? it is rather surprising how much less the
discrepancy becomes. An analysis of important estimates will therefore
be undertaken in order to try to discover some of the sources of

The most significant thing about an estimate is that the estimator is
thinking of providing for his group of deficients in a special way. This
is the purpose of the estimates. Three important groups of the mentally
deficient now demand attention. They are: (1) The group which, for moral
and eugenic reasons, society is justified in isolating for life or an
indefinite period. (2) The group which needs special simple industrial
training in order to get along with social assistance without isolation.
These deficients may be cared for in their home towns by special
schools, public guardians, and after-care committees. (3) The group
which needs special school assistance, but is socially passable after
leaving school. These individuals are incapable of competing in school
with their fellows, but they are able to get along in the simplest
employments without social assistance. We may designate these three
groups as those needing (1) social isolation, (2) social assistance, and
(3) only school assistance. The largest estimates of feeble-mindedness,
it will be found, include the third group, while the smallest intend to
include only the first group. The first and second groups are clearly
below the limit of feeble-mindedness designated by the verbal definition
of the British Commission. They are socially unfit. The language of that
definition is ambiguous enough to include the third group, but the plan
of the Commission, judged by its consideration of the number to be sent
to special schools, would regard only the first two classes as
feeble-minded. Following this common conception I have regarded those in
the third group as above the feeble-minded. It will help to find harmony
among the estimates if we estimate separately those mentally deficient
enough to need social isolation, social assistance, and only school
assistance. This discrimination of the retarded by the kind of social
care needed should also make the social definition more useful.


Before we consider the percentage estimates in detail for these
different forms of social care, let us note the effect on them of two
other considerations. The first of these is the discrepancy between
estimates of the proportion of feeble-minded among school children and
estimates as to the proportion in the general population. Since
feeble-mindedness is regarded as a permanent arrest of mental
development occurring at an early age and usually due to hereditary
causes, it is plain that a school child who is feeble-minded would be
expected to remain so for life. Nevertheless we find that estimates of
0.3% of the general population are accompanied by estimates of 1.0% or
2.0% of the school population as feeble-minded. I have not been able to
find any careful attempt to account for these discrepancies. The
excessive mortality among the feeble-minded is hardly adequate to
explain so great a difference.

It is interesting to note some of these comparisons. Goddard, for
example, considers it conservative to estimate that 2% of the school
population is “feeble-minded” (_112_, p. 6). In the same publication he
says: “There are between 300,000 and 400,000 feeble-minded persons in
the United States” (p. 582). Since the elementary school enrollment is
about 20,000,000 (_208_), the feeble-minded school children alone on his
first estimate would account for 400,000 feeble-minded in the United
States without allowing for any feeble-minded outside of the ages in the
elementary school.

The report of the British Royal Commission, published in 1908, forms the
starting point for many of the estimates made today. The commission
added together the number of school children which were thought to
require special classes with the number of defectives found in
institutions, prisons and almshouses, or reported by its medical
investigators. The total gave 0.46% of the general population as
“mentally defective persons,” not including certified lunatics. From
this amount should be deducted .06% who were insane but had not been
certified as such, leaving 0.4% mentally deficient. This was not
regarded by the Commission as an estimate, but was the number actually
“enumerated by the medical investigators” in sixteen typical districts
studied in England and Wales with a total population of 2,362,222 (_83_,
VIII, p. 192). Turning to the school children we find that in the areas
investigated there were 436,833 school children of whom 0.79% were found
defective. Since this was an enumeration and not an estimate, the
commission paid no attention to the discrepancy between 0.79% of the
school children and 0.31% of the rest of the population. Tredgold,
moreover, based his estimates of the frequency of the mental deficiency
in England and Wales on the data of the Royal Commission without
attempting to harmonize this discrepancy. This oversight has apparently
been one source of the not uncommon difference between the estimates for
school children and for the general population. One suspects that the
fact that the elementary school population is about a fifth of the
general population, has also mistakenly contributed to this error. The
discrepancy of three to five times as large a frequency of deficiency
among school children as in the general population certainly needs
clearing up.

There is an escape from this dilemma which seems more reasonable than to
attempt to account for the discrepancy by excessive mortality. When
estimates are made concerning the school population the estimator is
usually thinking of that group of feeble-minded which needs special
school training and probably social assistance afterward. When estimates
are made of the general population the estimator is likely to be
thinking of that group which must be cared for permanently by society,
mainly in institutions or colonies. For some time at least the state
cannot be expected to undertake the indefinite care of all the
deficients who should have, at once, simple industrial training, in
special local schools or classes in order to survive, even with social
assistance. This difference in the type of care contemplated seems most
naturally to account for the discrepancy found with many writers,
between their estimates for the school population and for the general


A second source of confusion arises when one investigator is thinking of
the number of feeble-minded, the care of whom it is _desirable_ that
society should assume, and another is thinking of the feeble-minded, the
care of whom it is _advisable_ for society to assume at once. Considered
in connection with a specific case the distinction is quite obvious. It
is one thing to say that it would be desirable for the state to assume
the indefinite care of a particular person, it is quite another thing to
say that it would be advisable for the state to assume that care
immediately, when one remembers the crowded condition of the
institutions, the necessity of caring for the worst cases first, the
possibility of the person being cared for by his own family or in a
local school, the added public expense, the necessary neglect of other
movements for social welfare if society assumes this expense, etc., etc.

When you magnify this problem in the mind of the estimator who is
interested in the question of caring for the groups of feeble-minded,
the result is that his estimates of the size of the groups are decidedly
affected. For example, few would deny that the Site Commission of New
York appointed to locate the colony for mental defectives, now known as
the Letchworth Village, was emphasizing a program of permanent social
care when it estimated the number of feeble-minded in New York. The
Commission, “after taking into consideration the figures of the State
and National census, and other data collected from institutions,”
estimated that there were in New York state possibly 12,300 mentally
defective persons (Editor's Note, _205_, p. 84). This is less than 0.15%
of the population and very low compared with most estimates.

The low estimates will generally be found to be influenced by
considerations of public expense rather than the social unfitness of the
lower group. Inasmuch as there are no sharp distinctions between
different degrees of mental ability this consideration of public expense
is perfectly proper. At the other extreme, however, are the eugenists
who are convinced that it is _desirable_ to isolate a large group at the
lower range of ability. The member of the legislature will be concerned
mainly with the question how much money will the public be willing to
appropriate now for the care of these unfortunates. The eugenist will be
thinking of an ideal rather far in the future towards which to work.

The diagnostician should take a conservative intermediate ground. He may
leave to the court or other authorized tribunal to decide whether the
public has the facilities available at present for caring for a
particular weak-minded person, but he must decide whether expert
scientific opinion at the present time will justify diagnosing this
degree of deficiency as suitable for the special care provided for the
feeble-minded. Whether it is advisable to care for the particular
deficient at home, in a special local school, or in a state institution
would be left to the legal authority to decide. Under present
conditions, the diagnostician may possibly indicate whether the
individual is deficient enough to justify social isolation, or merely to
justify sending to a local elementary day school for deficients.


It is from the point of view of the diagnostician that we shall attempt
to focus this question of the percentage of feeble-minded. We shall
tentatively suggest limits as to the degrees of _intellectual
deficiency_ which we might be justified in regarding, under the present
conditions of scientific knowledge as being low enough in intellectual
capacity to justify particular forms of social care. Such estimates will
be of value if they help to harmonize the conflicting opinions by
bringing them into relation with the above analysis. We shall,
therefore, compare the suggested percentages with a number of
authoritative statements of the frequency of feeble-mindedness. By
considering the differences in the nature of the estimations we may
approach nearer to an understanding of the problem.

Since the percentages to be suggested are chosen from the point of view
of diagnosis, they do not represent the number for which every community
should immediately make financial provision. The expense is a local or a
state question. It is so much affected by state conditions and by public
policy that it probably must be determined in any state by a special
commission. On the other hand, the laws already provide for caring for
the feeble-minded in institutions or colonies and in special schools or
classes, so that the estimates may help to guide diagnosticians who are
called upon to decide whether a particular person might be rightfully
regarded as deficient enough intellectually to justify committing him
for permanent care to a state institution. In the present practise it is
fairly clear that this distinction is made in the minds of different
diagnosticians. It may ultimately be desirable that this differentiation
between the types of social care be introduced into the law. Until then
it will remain the duty of the court to determine what degree of social
unfitness is intended by a particular law. The social concept of
feeble-mindedness is just now undergoing a rapid evolution so that it
would be impossible to predict how it may legally crystallize a
generation hence.

To begin with the lowest group of the feeble-minded, we should consider
those whom the state might be clearly justified in isolating
indefinitely on the basis of their tested lack of intellectual capacity,
the social isolation group. For purposes of comparison let us place this
degree of intellectual ability as that possessed by the lowest 0.5% at
fifteen years of age. Above these let us estimate a group of uncertain
cases so far as isolation is concerned, but cases which the
diagnostician would be justified in regarding as intellectually
deficient enough to justify sending to special local schools for
training the feeble-minded. After special training the majority of these
cases might be expected to require social assistance indefinitely. They
would form the social assistance group. Isolation would be justified for
none of them on the basis of their test records alone. Those in this
group who were persistent delinquents would, by that additional fact,
fall into the lowest group so far as social care is concerned. Let us
estimate this social assistance group tentatively as the next 1.0% at
fifteen years of age.

These estimates have been made as at fifteen years of age since the
effect of the excessive mortality especially among the isolation group
is uncertain and may need to be allowed for in a discussion of the
percentage deficient at different ages. If the mortality were as great
as has been described among institutional cases in the previous chapter,
a rough estimate of the percentage intellectually deficient in the
general population places it at less than 0.5%. This estimate may be
made by using the estimated deficiency at the median age of those under
15 years of age and at the median age of those 15 years of age and over.
According to the age distribution of the 1910 census, there were 32%
under 15 years with a median age of 6 years. At age six 0.67% would be
presumed as low as 0.50% at 15 years. The older group (68% of the
population) has a median age of 32 with a corresponding percentage in
the isolation group at that age of 0.30%, after allowing for differences
in mortality on the plan indicated in Table II. This rough estimate for
the lowest group indicates that 0.42% of the general population would be
of as low a degree of intellectual capacity as the lowest 0.5% at 15
years. Our plan presumes, therefore, that between 0.4% and 0.5% of the
population are unable to pass their entire lives outside of institutions
under ordinary conditions; _i. e._, make an honest living and live
within the law even with social assistance and supervision.

The corresponding estimate for those requiring only social assistance
would be between 0.8% and 1.0% of the general population above the
lowest group. This might vary from approximately 1.34% at 6 years to
0.59% at 32, the median age for those over 14 years. Since the mortality
is probably less among deficients not in institutions, as they average
higher in ability, the changes in the percentages are probably extreme
estimates. We should keep in mind, however, the possibility that with
the excessive death rate the lowest 1.0% at 15 may mean an ability
corresponding to the lowest 1.34% at 6 years and the lowest 0.60% at 32

The next higher group in intellectual ability is so high as not to
require social assistance outside of school. When we ask how large a per
cent. we should be justified in placing in this group and separating
merely for special instruction in school, we reach a condition which is
at present so ill-defined even in the minds of educators that it seems
best to fall back on the general advice that our school systems should
provide just as nearly individual instruction as the public purse and
managing genius can devise. Mannheim, Germany, for example, takes care
of 18 per cent. outside of its regular school classes. The ideal is
individual instruction for all. School authorities would be justified in
providing special instruction for every degree of mental ability, if the
cost would not restrict other more important social undertakings. This
less degree of retardation in the group needing only school assistance
should not, however, be classed as feeble-minded. We shall see later the
percentages for which some authorities have considered it already
advisable to provide special school instruction. We need not attempt to
estimate the size of this group, as it is beyond the limit of

The purely conative cases are not taken care of in the above estimates,
which are intended for tested deficients. If the conative cases
unaccompanied by intellectual deficiency should be regarded as frequent
enough to replace those in the social assistance group who ultimately
care for themselves, plus those subtracted by the excessive death rate,
we would have a total of 1.5% of the general population feeble-minded
enough to warrant social care of some sort. About 0.5% might justly be
isolated. The reasonableness of this program can be judged by comparison
with authoritative estimates now to be reviewed. The problem here is
whether this is an unreasonable program for the diagnostician to assume
as scientifically justified, remembering that these estimates are for
tested deficients at 15 years of age and do not include purely conative
cases which might occur above these intellectual borderlines.


_The Social Isolation Group._ We are now ready to consider some of the
important estimates which throw light upon the reasonableness of the
percentages we have named. First, what percentage would we be justified
in socially isolating? In the United States Census Report on the Insane
and Feeble-Minded in Institutions in 1910, we find that the number then
actually in institutions for feeble-minded was only about 0.02% of the
population. At the most frequent ages this rises to about 0.05%. It is
evident that the number actually isolated is of little significance
except as a check on the estimates. The report, however, refers to the
special estimate made by the public authorities in Massachusetts which
also included feeble-minded in state hospitals for the insane, other
asylums, those reported by the overseers of the poor and those
enumerated in the general population. The U. S. report says: “The census
was not regarded as being complete, but it is of interest to note that
if the number of feeble-minded in proportion to the total population was
the same for the entire United States as it was in Massachusetts
according to this census, the total number of feeble-minded would be
over 200,000. Probably this may be regarded as a conservative estimate
of the number of feeble-minded in the United States and would indicate
that not over one-tenth of the feeble-minded are being cared for in
special institutions” (_205_, p. 183). This estimate, which thus amounts
to about 0.2%, may probably be considered as a reasonable program of
expansion from the institutional viewpoint. The diagnostician who is
considering the individual and not the mass must supplement it by
considering who should be isolated if facilities were available. If the
census bureau can contemplate institutional care for ten times those at
present thus provided for, it gives us some indication of a reasonable
limit as to the increase in institutional care that can be assumed to be
reasonably contemplated at present.

Dr. W. D. Cornell, director of medical inspection of the Philadelphia
public schools, after the personal examination of those cases which in
the opinion of the teachers should be sent to institutions, places the
“institution cases” at a minimum of 15 per 10,000 school children. He
adds: “The number of evidently feeble-minded above 6 years of age may be
said to be 1 to every 500 of the population. These figures are
conservative and have been accepted by experts for years.” This then is
the minimum estimate and quite clearly refers to institutional cases.

A committee of the Public School Alliance of New Orleans, of which Prof.
David Spence Hill was chairman, reported in 1913 a careful census of the
public school children in that city the previous year made by the
teachers in co-operation with the Newcomb Laboratory of Psychology and
Education. Each teacher was asked to state her opinion as to how many in
her room were “feeble-minded or insane children who should be under
institutional or home care, rather than in the public schools.” Also the
number of backward children not in the above class “who urgently need
special educational methods in special classes within the special
schools.” About a fifth of the total of the 38,000 school children in
the city are colored. The grand total showed 0.28% in the first class
mentioned above, and 7.7% in the second. Speaking of those “thought by
teachers to be feeble-minded” and needing institutional care the report

“The figure 0.28 of 1% coincides exactly with the estimate of the
Philadelphia Teachers' Association made in 1909 in a census of 150,000
school children. Secondly, while the teacher's estimates are open to
revision, nevertheless her judgment, as inevitably evidenced in her
attitude toward the child, is the _practically effective judgment_”
(_157_, p. 6). It is a well-known fact that teachers tend to
underestimate the frequency of mental deficiency, so that it would
certainly be a matter of regret if this were to continue to be the
“practically effective judgment.”

Another census of the institutional type of feeble-minded made by the
Director of Public Health Charities in Philadelphia and reported in 1910
enumerated 0.2% of the population as in this group. It included cases in
the institutions for feeble-minded, the insane hospitals, almshouses,
hospital, reformatories, orphanages and known to charity workers (_168_,
p. 13).

One of the most careful surveys of individuals who, because of mental
abnormalities, show such social maladjustment as to become the concern
of public authorities was made under the auspices of the National
Committee for Mental Hygiene in 1916.[5] It selected Nassau County as
representative of New York state. Part of the survey consists of an
intensive house to house canvass of four districts of about a thousand
population each. The result disclosed that 0.54% of the population of
this county were socially maladjusted because of “arrests in
development” and 0.06% more, because of epilepsy. This was in a
population of 115,827.

The Children's Bureau in the U. S. Department of Labor in 1915 made a
census of the number of “mental defectives” in the District of Columbia.
The census included only those whom we have termed feeble-minded. The
report states that 798 individuals, 0.24% of the population, were found
to be “in need of institutional treatment; and the number reported,
allowing for the margin of error in omission and inclusion, is probably
a fair representation of the number in the District who should have
custodial care” (_88_, p. 13). Over a quarter of the population of the
District is colored. The census was taken in connection with plans for
immediate care. The same Bureau also made in 1915 and 1916 a Social
Study of Mental Defectives in New Castle County, Delaware.[6] This
county had a population of 131,670 and the survey disclosed 212
“positive cases of mental defect” and 361 “questionable cases,” a total
of 0.44% of the general population in this county. Among the positive
cases, 82.5% were in need of public supervision or institutional care.
Among the questionable cases, information was obtained about only 175,
and 165 of these were either in institutions, delinquent or
uncontrollable, or living in homes where proper care and safeguarding
were impossible.

Two other important attempts to enumerate carefully all the
feeble-minded in definite areas in the United States have been made in
recent years. Lapeer County, Mich., was chosen for such a study, as it
was of average size and contained no large city. The census as reported
in 1914, showed 36 feeble-minded from that county in the state
institution and 116 others living in the county, a total of 1 from every
171 inhabitants (_145_). A special children's commission was appointed
by the state of New Hampshire to investigate the welfare of dependent,
defective and delinquent children. Its report in 1914 contained a
section by its chairman, Mrs. Lilian C. Streeter, on feeble-mindedness
(_40_). This comes the nearest to a complete enumeration for an entire
state which has ever been attempted. The commission tested with the
Binet scale the inmates of the State Hospital for the Insane, the County
Farms, the State Industrial School and the Orphanages within the state.
The borderline which it used for the scale was high. It counted all
those testing three or more years retarded and under XII as
feeble-minded. Taking its figures as they stand we find that they listed
947 as feeble-minded in institutions and 2,019 outside, a total of 0.69%
of the inhabitants of the state. Outside the institutions the commission
sent a questionnaire to all school superintendents and to chairmen of
school boards, physicians, overseers of the poor, county commissioners,
probation and truant officers, district nurses and charity workers
throughout the state, by which means they listed 792 additional cases.
This questionnaire gave the following description of the type of case it
was trying to list as feeble-minded.

  “The high grade imbecile, frequently known as the moron, is one who
  can do fairly complicated work without supervision, but who cannot
  plan, who lacks ordinary prudence, who cannot resist the temptations
  that are common to humanity. The high grade imbecile is most
  dangerous because, except to the expert, he is apparently not
  feeble-minded and is, therefore, usually treated as normal, and
  permitted to multiply his kind, and to corrupt the community.”

This description would tend to include cases above our isolation group.
Besides the questionnaire the commission made an intensive study of 52
towns in which it says practically complete census returns were obtained
by consulting doctors, school and town officials. With these
supplementary cases it secured a list of 2,019 cases outside of
institutions, making a total of 2,966 recorded cases within the state or
0.69% of the population. When it estimated the proportion for the entire
state on the basis of the rate of canvass returns to questionnaire
returns, this proportion rose to 0.95%. The commission does not advocate
compulsory isolation for all of these people although it recommends
custodial care for the feeble-minded women and girls of child-bearing
age, apparently of the degree of deficiency represented by its criteria.
This enumeration of 0.69% of the people of a state as feeble-minded is
the most liberal general census of the feeble-minded in any large area.
It clearly shows the trend of diagnosis since the British Census.

The Extension Department of the Training School at Vineland, N. J.,
states regarding estimates of the number of feeble-minded in the general
population: “Conservative estimates give one in three hundred as the
probable present number.” Under the discussion of estimates of the
general population I have already cited Goddard's estimate which was
approximately 0.3 to 0.4% and the enumeration of 0.4% by the British
Royal Commission in 16 districts with over two million population. While
all of these estimators are speaking broadly of the feeble-minded, in
the general population, we shall not be far wrong in supposing that they
are considering mainly those deficients for whom the state might well
expect to provide care for life, isolating all those who cannot be
eugenically guarded at home. We shall later quote the estimate of Van
Sickle, Witmer and Ayres of 0.5% of the school population as
“institution cases.”

Our estimate of 0.5% in the group justifying isolation on the ground of
intellectual deficiency seems to be conservative and to harmonize fairly
this type of estimate.

_The Social Assistance Group._ Passing now to the next higher group of
deficients, those needing special training in order to get along with
social assistance, the estimates have been based almost entirely upon
the study of school children. Francis Warner was the moving spirit in
the early investigations in Great Britain, which were made without tests
from 1888 to 1894. The census which he directed included about 100,000
school children who passed in review before medical examiners. As cited
by Tredgold (_204_) the estimate growing out of this work was that 1.26%
of the school population should have instruction in special classes. Of
these 0.28% required special instruction because of physical defects
only (_204_).

About the same time Will S. Monroe (_155_) on the basis of a
questionnaire sent to California teachers, who reported on 10,842 school
children, found that they estimated 1,054 of these as mentally dull in
school, 268 feebly gifted mentally, and 6 imbeciles and idiots. He
summarized his conclusion as follows: “A long experience teaches that
every school of fifty pupils has at least one child that can be better
and more economically trained in the special institutions than in the
public schools.” In his estimate of 2% he was probably thinking of care
in special local schools and not permanent isolation.

A government inquiry of school teachers in Switzerland, who had charge
of 490,252 school children, reported that 1.2% were so feeble mentally
as to need training in special classes. Only about a tenth of this
number were then being instructed in separate classes (_181_, p. 17).

Great Britain first gave legal recognition to the class of feeble-minded
above the imbeciles in its Education Act of 1898, following a report of
a departmental committee of its National Board of Education growing out
of the inquiries of Francis Warner. This committee estimated the
proportion of this class as approximately 1% of the elementary school
population (_181_). In discussing the comparative estimates on the
general and school populations I have already referred to the estimate
of Tredgold based upon an elaborate analysis of the most extensive data
ever collected,—that gathered by the British Royal Commission on the
Care and Control of the Feeble-Minded. While the Commission's
investigators enumerated 0.79% among the school as mentally defective,
Tredgold's estimate based on his analysis of their report was that 0.83%
of the school population in England and Wales were above the grade of
imbecile but still feeble-minded (_204_, p. 157). The variability of the
estimates collected by the Royal Commission from various cities probably
indicates the subjective character of the standards of deficiency. They
varied from an estimate of 0.24% of the elementary school population in
Durham to 1.85% in Dublin (_204_, p. 159). The Commission says regarding
estimates as to communities other than those reported by their medical
investigator, for Newcastle the “number of feeble-minded children of
school age” (morons) was 0.25%, for Leeds the estimate was 0.80%, for
London 0.50% or 0.60%, for Bradford 0.50%, for Dublin about 1% and for
Birmingham about 1% of the school population. Dr. Francis Warner's
general estimate was 0.8%. We have thus variations in estimates from
0.25%, 0.5%, 0.80% to 1% and some 2% (_167_, p. 90). For the rural areas
the estimates were generally less.

A careful estimate has been made with a different method by Karl Pearson
on the basis of a classification by teachers of school children in Great
Britain into nine different classes each especially defined and
extending from the imbecile to the genius. This distribution of the
children was then fitted to the normal probability curve. On this basis
Pearson estimated that 1.8% would fall in the “very dull group,” defined
as having “a mind capable of holding only the simplest facts, and
incapable of grasping or reasoning about the relationship between facts;
the very dull group covers but extends somewhat further up than the
mentally defective.” Lower down would be 0.1% in the imbecile group. He
says further regarding this estimate: “It is deduced from three series
covering between 4000 and 5000 cases, and the three separate results are
in several accord. It will, I think, be possibly useful for other
inquirers, and it endeavors to give quantitative expression to our
verbal definitions of the intellectual categories” (_166_).[7]

In 1914 Pearson cites estimates of mentally defective children in
several cities by teachers and medical officers based upon the
recommendation of elementary school children for special schools and
classes. These were, for London: boys, 1.59%; girls, 1.09%. For
Liverpool: boys, 0.827%; girls, 0.618%. The corresponding figure for
both sexes in Stockholm is 1.23%. He concludes that “something between
1% and 2% is true for England. Dr. James Kerr, Medical Research Officer,
thinks that the final estimate will be nearer the latter value.”

After giving a table of the percentages at each age in the elementary
schools of Stockholm, Pearson says: “Judged from this table it would
seem that the most reasonable estimate of the prevalence of mental
defect is to be formed when all the mental defectives have been
definitely selected and the normal children have not yet begun to leave
school, _i. e._, at the ages 11 and 12. For Stockholm this leads up to a
mentally defective percentage of about 1.5” (_167_, p. 6-8). In another
place he says that the members of special classes are selected
practically for the same reason, _i. e._, because they are school
inefficients, the bulk of whom will, no doubt, unless provided for
become “social inefficients” (_164_, p. 48). Since some were not
selected because of intellectual deficiency, our social assistance group
should be somewhat smaller.

In 1909-10 the actual number in the schools for mental defectives
maintained by the London County Council was 0.9% of the enrollment of
the London elementary Schools (_143_). The 1912 report of the London
County Council shows 7357 children enrolled in its local schools for
mental defectives, which is 1.1% of the average attendance from
1912-1913 in the elementary county council schools and voluntary schools
of London (_144_, p. 44).

Following a discussion in the Australian Medical Congress of 1911 the
Minister of Public Instruction called for returns as to the number of
feeble-minded in the Australian public elementary schools between 5½ and
14 years of age inclusive. The questionnaire used the definitions of the
British Royal Commission as a description of the various degrees of
retardation and brought returns from 2,241 of the state schools, all
except 57. For their average attendance of 175,000 children, these
teachers classified 1.9% as backward from accidental causes, 2% mentally
dull, 0.42% feeble-minded imbeciles or idiots, and 0.6% epileptics. To
this would be added 0.19% for children in the idiot asylums. The report
states that “the teachers' estimates will thus be realized to be an
absolute minimum, dealing only with the intermediate grades, and not
including the gross cases (idiots, etc.) on the one hand and the less
marked high grades of feeble-minded on the other” (_70_).

The census made by the Bureau of Health of Philadelphia through the
principals of schools in 1909 covered 157,752 elementary school children
of whom 1.9% above the 0.28% who could “properly be in custodial
institutions 'were classed' as backward children who require special
instruction by special methods in small special classes” (_168_).

A survey of the school population in the Locust Point District of
Baltimore was made by Dr. C. Macfie Campbell.[8] The district surveyed
was, however, not considered typical of Baltimore, but was a sample of
an industrial district in which the majority of families are “close to
the poverty line, and too often below it.” Out of a school population of
1,281 children, 166 (13%) were “found to have special requirements on
account of their mental constitution.” Among these, 22 (1.7%) “showed a
pronounced mental defect, which eliminated any prospects of their
becoming self-supporting.”

The city of Mannheim (_147_), which perhaps cares for its exceptional
children better than any other in the world, was in 1911-1912 caring for
0.7% of the children in its _Volkschule_ in _Hilfsklassen_ which do not
take them beyond the fourth grade. There were 12% more who were backward
in school and being taught in _Forderklassen_ where they may reach the
sixth grade. Including the exceptionally bright who were also in special
classes, 18% all together of its school children were not in the regular
_Hauptklassen_ of the eight grades. To these would be added those sent
to special institutions. When we estimate, therefore, that we are
justified at present in sending 1% of the children in school to special
classes because their intellectual deficiency is such that the bulk of
them cannot get along without social assistance, we are naming about the
proportion already thus cared for in several foreign cities.

Among the authoritative estimates of the number of feeble-minded, which
have been made by estimators who had in mind the evidence from mental
tests, is that made by James H. Van Sickle, Lightner Witmer, and Leonard
P. Ayres in a bulletin published by the United States Bureau of
Education in 1911 (_209_). They state that, “if all children of the
public schools could be ranked, it is probable that a rough
classification would group them about as follows—Talented, 4%; Bright,
Normal, Slow, 92%; Feeble-Minded, 4%. The 4% may for administrative
purposes be divided into two groups. The lower one includes about
one-half of one per cent. of the entire school membership.... They are
genuinely mentally deficient, and cannot properly be treated in the
public schools. They are institution cases, and should be removed to
institutions. Ranking just above these are the remaining three and
one-half per cent. who are feeble-minded but who could be given a
certain amount of training in special classes in the public schools.”
The estimate of institutional cases practically coincides with that
adopted above in this paper. The extension of the term feeble-minded to
include the lowest 4% seems to be extreme. The authors do not suggest
what portion of these they think might require social assistance
indefinitely, but are interested primarily in provision for special
classes in the public schools. If the term feeble-minded were to mean
only unfit for regular school classes and not socially unfit, I have
already suggested that the limit for special instruction might be
increased indefinitely. In Mannheim 18% are not cared for in the regular

The only estimate of feeble-minded which I have found that is so large
as this 4% is that of Binet. It is also intended to cover all cases that
should be sent to special classes regardless of subsequent social
survival. His statement as to those who are so abnormal or defective as
to be suitable for neither the ordinary school nor the asylum is as

  “As to France, precise information has not been available until the
  last year, when two inquiries were held—one at the instance of the
  Ministerial Commission, the other organized by the Minister of the
  Interior. According to the former inquiry we find that the
  proportion of defectives amounts to scarcely 1% for the boys, and
  0.9% for the girls. These percentages are evidently far too small,
  and we ourselves have discovered, by a small private inquiry, that
  many schools returned “none” in the questionnaires distributed,
  although the headmasters have admitted to us that they possessed
  several genuine defectives. In Paris, M. Vaney, a headmaster, made
  some investigations by the arithmetic test, which we shall explain
  presently, and reached the conclusion that 2% of the school
  population of two districts were backward. If we were to include the
  ill-balanced, whose number is probably equal to that of the
  backward, the proportion would be about 4%. Lastly and quite
  recently a special and most careful inquiry was made at Bordeaux,
  under the direction of M. Thamin, by alienists and the school
  medical inspectors, and it was found that the percentage of
  abnormality amongst the boys was 5.17. Probably the true percentage
  is somewhere in the neighborhood of 5. All these inquiries are
  comparable because they deal with the school population” (_77_, p.

In this estimate of 5%, Binet was considering those to be sent to
special classes regardless of whether or not they would require
indefinite social assistance after their schooling. It is therefore not
directly comparable with our estimate of 1.5% presumably or doubtfully
intellectually deficient.

The estimate of Dr. Henry H. Goddard, who has done the most to introduce
the Binet Measuring Scale in this country, is stated as follows: “It is
a conservative statement to declare that 2% of public school children
are distinctly feeble-minded, the larger part of them belonging to this
high-grade group which we call morons” (_118_). In another (_114_) place
he says: “The most extensive study ever made of the children of an
entire school system of two thousand has shown that 2% of such children
are so mentally defective as _to preclude any possibility of their ever
being made normal and able to take care of themselves as adults_.”[9]
The study to which he refers gives individual results with the Binet
1908 tests made on 1547 school children in the first six grades (_114_,
p. 43). Since the sixth grade does not include the better children who
are twelve years or over in age this group is clearly selected in such a
way that it would show an excessive percentage of mentally retarded
children. We find in the investigation referred to that he says: “Then
we come to those that are four years or more behind their age, and here
again experience is conclusive that children who are four years behind
are so far back that they can never catch up, or in other words, they
are where they are because there is a serious difficulty which can never
be overcome—they are feeble-minded. They constitute 3% of the children
in these grades.”

Since we have a random selection of school children in his table for
only those children who are 6 to 11 years of age inclusive, I find that
only 1% at these ages are retarded four years intellectually. On his own
basis, therefore, 3% is evidently too large an estimate. Later he seems
to have reduced his estimate to 2% of the school population. Of those
who test in the lowest 1.5% including our doubtful group, I believe that
there is no clear evidence that more than 1% will require even social
assistance as adults.

Many more estimates of the number of feeble-minded among school children
might be cited, but they would add little to these authoritative
samples. At the present time an estimate by health officers or teachers
who are not familiar with the results of mental testing has little
significance, as the whole complexion of the problem has been changed
since the work of Binet and Simon.[10] We may, however, cite three
estimates based upon familiarity with test results, which fairly cover
the range of estimates among school children. In connection with the
Springfield, Illinois, survey conducted by the National Committee for
Mental Hygiene under the direction of the Russel Sage Foundation, we
find that three typical schools with a total of 924 pupils were studied.
The report states that “the mentally defective children” constituted
3.8% of the number in attendance in March. The number of children in the
schools examined, for whom instruction in special classes would be
desirable, is about 7% of the entire enrollment of these schools (_203_,
p. 10).

In connection with the Stanford Version of the Binet Scale, Dr. Lewis M.
Terman says: “Whenever intelligence tests have been made in any
considerable number in the schools, they have shown that not far from 2%
of the children enrolled have a grade of intelligence which, however
long they live, will never develop beyond the level which is normal to
the average child of 11 or 12 years.... The more we learn about such
children, the clearer it becomes that they must be looked upon as real
defectives (_57_, p. 10). Again in placing the borderline for
feeble-mindedness” with the Intelligence Quotient used, he suggests that
“definite feeble-mindedness” lies below an I. Q. of 70 which with 1000
quotients was found to exclude about the lowest 1%. Above this is a
group with I. Q.'s 70-80 which he describes as “borderline deficiency,
sometimes classifiable as dullness, often as feeble-mindedness.” This
group would include, as judged by the results of these tests, over 4%

Dr. Wallin, who has had wide experience in testing both school children
and defectives, states: “I will venture the assertion, after years of
teaching in the public schools and clinically examining public school
cases, that the oft-repeated statement that 2% of the general school
population is defective (if by this is meant feeble-minded), exaggerates
the real situation. The actual number is probably about 1%” (_211_, p.

After reading a paper on “A Percentage Definition of Intellectual
Deficiency” before the American Psychological Association in 1915
(_151_), I was pleased to discover that Prof. Rudolf Pintner and Donald
G. Paterson were also about to propose a percentage definition of
feeble-mindedness for those who are dealing with mental tests (_44_).
While their idea seems to be fundamentally similar, their paper shows
that their conception is to be sharply distinguished in several
particulars from that which I am advocating. They would limit the use of
the term “feeble-mindedness” to individuals who test in a rather
arbitrarily chosen lowest percentage of the population. As opposed to
this I suggest continuing the present social definition of
feeble-mindedness and supplementing it, for the purpose of aiding in the
diagnosis, by indicating the social significance of those testing in
certain lowest percentages. Such tested deficients I designate as
“intellectually deficient.” It is important to consider their statement
and to note what percentage they have chosen to regard as feeble-minded.
They say:

  “It is in order to avoid this vagueness and uncertainty attaching to
  the term that we suggest a definite psychological concept. The
  lowest three per cent. of the community at large, that is, the
  lowest as determined by definitely standardized mental tests, are to
  be called feeble-minded. Such a definition will be unambiguous and
  the dividing line between this and other groups will become clearer
  and clearer as we increase the accuracy of our measuring scales and
  the adequacy of our standardizations. Furthermore, if evolution is
  raising the degree of intelligence the three per cent. at the lower
  end will still remain, for, whatever the degree of their
  intelligence may be, they will still be feeble-minded as compared
  with the normal.

  “Such a definition will in addition restrict the term to such as are
  lacking in intelligence and will differentiate them from the moral
  defectives and the psychopathic personalities, which are at present
  often confused with the group that we propose to call feeble-minded.
  An individual may be at the same time a moral defective and
  feeble-minded, but there is reason to believe that moral deficiency
  may exist without such intellectual defect as to warrant a diagnosis
  of feeble-mindedness. The same may be said of the psychopathic

  “The further question, whether all those coming within the proposed
  definition of feeble-mindedness are to be confined in institutions,
  is purely social and will be determined by the social needs of each
  community and does not concern us here. It is obvious that many more
  in addition to the feeble-minded as defined by us will require the
  restraint of an institution, even though no real mental defect

  “It is immaterial for the purposes of this hypothesis whether three
  or a smaller or larger percentage be designated as feeble-minded.
  The important point is the agreement upon some fixed percentage, and
  we have chosen three per cent. as covering presumably all the cases
  of marked mental deficiency. A brief glance at the chief estimates
  of the number of feeble-minded in civilized communities would
  indicate that our percentage is somewhat higher than the
  conservative writers give, but we shall show later on that it is
  much lower than the results obtained from groups of children tested
  by intelligence scales” (_44_, p. 36).

With those who understand that deficiency is mainly a question of
degree, it would seem that there might be some agreement as to the plan
for defining tested deficiency. In order to make this plan more useful
to those dealing with the social care of the feeble-minded, it would be
necessary to supplement the bare percentage definition by relating it to
expectations of social failure somewhat after the manner I have
attempted. In particular it will gain its main value for diagnostic
purposes, it seems to me, if the percentage is so chosen that it may
receive the support of conservative scientific opinion. To be most
useful it seems evident, also, that the percentages must be chosen with
regard to the sort of social care which it is anticipated would be
_justified_ for the particular degrees of deficiency.

Let us recall the percentages suggested to harmonize the estimates: the
lowest 0.5% to be regarded as presumably deficient enough to justify
isolation and the next 1% as doubtful, but low enough to warrant special
training and probably requiring indefinite social assistance. If these
percentages for tested intellectual deficiency have been shown to be
fairly conservative estimates in the light of the authoritative
judgments with which they have here been compared, the laboriousness of
this comparison has been worth while. Further light upon the social
assistance group may be thrown by the study of the success of those
children who have already had the advantage of training in local classes
for the deficient.

                           SPECIAL TRAINING.

That we are not justified in isolating all whom we class as
feeble-minded is best indicated by the evidence as to the number of
these sent to special local classes for deficients who are able to float
socially with the assistance of capable after-care committees. A fair
picture of the present situation may be obtained by thinking of these
pupils in the help-classes and schools as representing about the next 1%
above those who have been isolated in institutions. With this picture in
mind let us see what has been the outcome of their special instruction
and social assistance thereafter.

In his book on Les Enfants Anormaux, Binet collected the evidence
available at that time (_77_, p. 140). He says:

  “Mme. Fuster, after a stay in Germany, where she visited some
  _Hilfsschulen_ and Hilfsklassen (literally, 'help-schools' and
  'help-classes') made a communication to the _Société de l'Enfant_,
  from which it appears that in the case of 90 classes for defectives
  in Berlin, 70% to 75% of the defective pupils who were there became
  able to carry on a trade; 20% to 30% died in the course of study, or
  returned to their homes, or were sent to medical institutions for

  “According to a more recent inquiry, made under the auspices of M.
  de Gizycki at Berlin, and published in a book by Paul Dubois, 22% of
  the children were sent home or to asylums; 11% were apprenticed; 62%
  worked at occupations which required no knowledge and yielded little
  pay (laborers, crossing-sweepers, ragmen). If we add together these
  two last groups, we reach a proportion of 73% of defectives who have
  been made, or who have become more or less useful....

  “Dr. Decroly has kindly arranged at our request a few figures
  relating to the occupational classification of the girls discharged
  from a special class in Brussels.... Finally, then, out of nineteen
  feeble-minded subjects, regarding whom particulars have been
  supplied, one-half, or 50%, have been apprenticed, or more than
  half, 75% if we count the defectives who 'work....'

  “Through the intervention of an inspector, M. Belot, we have
  inquired of twenty heads of schools what has become of the
  defectives whom they notified to us two years ago. We have made
  these inquiries with regard to sixty-six children only.... If we
  subtract the two first groups, those about whom the particulars are
  wanting, and those who have not yet left school, there remain
  twenty-seven children, of whom seventeen have been apprenticed, or
  76%.... Now this proportion is, by an unexpected agreement,
  identical with that obtained in the classes of Berlin and Brussels.”

A more recent report concerning the _Hilfsschulen_ in Berlin by Rector
Fuchs is in close agreement. It indicates that from 70% to 80% of the
former pupils of these schools make a living after they leave school.

To compare with these reports indicating that about three-fourths of
those leaving the special schools of Paris, Berlin and Brussels by
social assistance attain occupational classifications, we have less
favorable reports from Great Britain. Shuttleworth and Potts (_181_, p.
23) say:

  “At the Conference of After-Care Committees held in Bristol on
  October 22, 1908, a paper read by Sir William Chance, Chairman of
  the National Association for the Feeble-Minded, dealing with the
  reports of the After-Care Committees of Birmingham, Bristol,
  Leicester, Liverpool, London, Northampton, Oldham and Plymouth. The
  combined statistics from the nine centers showed that 22% of those
  who had attended special schools for the mentally defective were in
  regular work, and 6.8% had irregular work.... To illustrate the
  necessity for continuous supervision and the futility of temporary
  care, we cannot do better than quote the records of the Birmingham
  After-Care Committee, as embodied in their report for 1908, after
  seven years work. It was found that, 'out of 308 feeble-minded
  persons who have left school and are still alive, only 19.8% are
  earning wages at all, and only 3.9% are earning as much as 10 s. per
  week'” (_181_).

Tredgold summarizes other data on this question of industrial success as

  “We may next turn to the reports of 'After-Care' Committees
  regarding feeble-minded (moron) pupils of the special schools. In
  _London_ the proportion of pupils known to be in 'good or promising'
  employment was 37.5%. Two years previously it had been 45.7%, and
  Sir George Newman, the Chief Medical Officer to the Board of
  Education, attributes the falling off to two causes—_firstly_,
  insufficient after-care; and _secondly_, the two additional years.
  He remarks: 'The longer the test the more severe it is.' In
  _Birmingham_, the 'After-Care' Committee compiled information
  regarding 932 cases which had passed through the schools during the
  previous ten years. Of these, excluding the normal and dead, 272, or
  34%, were engaged in remunerative work. At _Liverpool_, of 712
  children passing through the hands of the 'After-Care' Committee
  during a period of six years, 85, or 11.9%, were doing remunerative

  “Finally we may refer to some figures concerning 'After-Care' work
  compiled by Sir William Chance from the returns of the National
  Association for the Feeble-Minded. These were based upon an inquiry
  made of sixteen centers of the Association, and referred to a total
  of 3,283 persons. Of this number, 798 were doing remunerative work,
  89 were 'doing work, but not reported;' 202 were useful at home; and
  941 were returned as 'useless members of society.' If we exclude 340
  who were transferred to normal schools (not being feeble-minded), we
  have 27% engaged in remunerative work.

  “With regard to the term 'remunerative work,' however, it is to be
  remarked that the person employed is not being paid the standard
  wage. On the contrary, it is my experience that this is practically
  never the case, and this is corroborated by the observations of the
  secretary of the Birmingham center, who says: 'Although some of our
  cases have been at work for more than ten years, only 34 of the
  whole number (173) earn as much as 10 s., 2 d., per week. Of these
  only 6 earn as much as 15 s., and only 2 earn 20 s., which is the
  highest wages earned.... While it is not very difficult for some of
  our higher-grade cases to get work when they first leave school, it
  is almost impossible for them to retain their situations when they
  get older, and the difference between them and their fellows becomes
  accentuated. Uncontrolled and often quite improperly cared for, they
  rapidly deteriorate, the good results obtained by the training and
  discipline of the special school being under these circumstances
  distinctly evanescent.... There are few workers over twenty years of
  age'” (_204_, p. 425, 435).

The 1912 report of the London County Council (_144_) covers those who
left its special schools for mentally defective children during the
years 1908-1912 inclusive. These schools have accommodation for about 1%
of the elementary school enrollment. Of 2010 children who left these
schools during these five years, and who were still alive, 1357 were
employed and 311 more employed when last heard from, a total of 79%
employed at last accounts. Those out for five years show about the same
proportion employed. This is a more favorable showing and fairly in line
with the results of other European help-schools. The average weekly
wages of those employed ranged from 4 s. 6 d. for those just out to 10
s. 10 d. for those leaving five years before. A considerable proportion
who live at home thus have been meeting their necessary living expenses
as the result of this special training and subsequent assistance.

Dr. Walter E. Fernald reported to the British Royal Commission on the
Care and Control of the Feeble-Minded concerning the inmates of the
institutions for feeble-minded in the United States. These institutions
receive a much lower grade of cases on the whole than the local
help-schools abroad: (_83_, Vol. VIII, p. 159)

  “Some of the institutions where only the brightest class of
  imbeciles are received, and where the system of industrial training
  has been very carefully carried out, report that from 20% to 30% of
  the pupils are discharged as absolutely self-supporting. In other
  words at other institutions, where the lower grade cases are
  received, the percentage of cases so discharged is considerably
  less. It is safe to say that not over 10% to 15% of our inmates can
  be made self-supporting, in the sense of going out into the
  community and securing and retaining a situation, and prudently
  spending their earnings.... But it is safe to say that over 50% of
  the adults of the higher grade who have been under training from
  childhood are capable, under intelligent supervision, of doing a
  sufficient amount of work to pay for the actual cost of their
  support, whether in an institution or at home.”

The wages of the women at the Bedford Reformatory before entering
prostitution as given by Davis (_133_, p. 210) have a direct bearing on
the earning capacity of the higher grade feeble-minded. The Binet tests
of Bedford women by Weidensall indicate that about 38% of the successive
cases admitted to Bedford test in the lowest 0.5% intellectually, and
75% in the lowest 1.5% intellectually. Davis' table shows that for 110
whom she classes as mentally low grade cases at the reformatory, the
median wage of those in domestic service, as claimed by the women, was
nearly $4.50 before entering prostitution. These feeble-minded women, if
their statements of earnings can be accepted, are therefore
feeble-minded by reason of their low intelligence plus delinquency, and
not by reason of inability to earn the necessities of life. The best of
these mentally low grade cases earned as high as $5.00 in addition to
board and lodging in domestic service and $25.00 outside of domestic

In this country we have fewer studies of the results of training the
mentally retarded in special local classes and schools. Miss Farrell has
made a preliminary report of 350 boys and girls out of the 600 children
formerly in the ungraded classes in New York City during the preceding 8
years (_102_). Omitting seven whose status was unknown and 10 who had
died, only 6% were known to have failed to survive socially with
assistance. These were in penal or other institutions. On the other hand
a strict analysis of her returns shows only 28% earning $5.00 a week or
more and thus possibly surviving independently. Of the above group of
333, 86 were at home, 192 employed, 31 unemployed and 3 married.

In Detroit among 100 children over 16 years of age who had attended its
special classes and been out of school not over 5 years, 27 had been
arrested, but 39 of the boys had been at work and received an average
wage of $7.00 per week, while 16 girls had averaged $3.75 in weekly
wages, although few held their positions long (_97_).

Bronner (_6_) compared a random group of thirty delinquent women at the
detention home maintained by the New York Probation Association with an
intellectually similar group of 29 women all of whom had been earning
their living in domestic service and none of whom had been “guilty of
any known wrong doing.” The delinquents were 16 to 22 years of age while
the servant group was somewhat older. Only two or three of the
delinquent group were worse than the poorest of the servant group in any
of the five intellectual tests, so that, if more than this number were
intellectually deficient, they were no more deficient than those who had
survived in society. No Binet scale records were published so that we
have no means of determining how many of these delinquents might fall
within either of our deficient groups.

The principal deduction from this evidence on the earning capacity of
those of low intellectual grade is a caution against demanding the
social isolation of all the intellectually weak until we have more
definite information as to what portion of them are able to live moral
lives, as well as earn their living with social assistance, without
being cared for entirely in isolation colonies. That a significant
number of the lowest 1.0% intellectually next above the lowest 0.5% have
led moral lives and have shown considerable earning capacity after
attending special schools, when they are given proper after-care, has
probably been demonstrated. They should, therefore, be treated as an
uncertain group whose feeble-mindedness would never be decided purely on
the ground of the intellectual tests. Most of them will, however,
probably be found mentally deficient enough to need at least social
assistance and protection.

In concluding this summary on the estimates of the frequency of
feeble-mindedness, it need only be added that so far as concerns the use
of the percentage definition for fixing the borderline in any particular
system of tests the percentages chosen are not essential to the plan.
The principles of the method apply whatever percentages might be
adopted. For such important purposes as the comparison of the relative
frequency of deficiency in different social groups and harmonizing the
investigations with different mental scales, agreement upon a particular
percentage is not essential. In diagnosis, of course, it is a matter of
fundamental importance in order that injustice may not be done
individuals. For this reason the estimate should be conservative,
possibly more conservative even than our tentative 0.5% at 15 years of
age. Any investigator who disagrees with the above estimates of the
degree of tested deficiency justifying isolation may substitute X per
cent. with a doubtful region extending Y per cent. further. Provided
such a census were legally authorized and funds available it would be
not impossible to get a reliable determination by a house to house
canvass showing the number of adult deficients, say 21 years of age, in
typical communities, who were not able to survive socially without
assistance. This number would then give the key for a conservative
percentage and the movement for early care would be immensely advanced.

With the recent introduction of psychological tests into the cantonments
of the national army, the goal of symptomatic borderlines as determined
by objective tests seems to be almost at hand. Since the men are brought
practically at random to the camps by the draft and are under military
command, it may be possible to find out the social history of a large
enough group at the lower limit of tested ability to establish the
question of the necessary capacity for independent moral and social
survival. These borderlines could then be transferred from the army
tests to positions of equivalent difficulty in other test systems.

The remainder of this study will show some of the advantages of the
percentage definition for fixing the borderlines with a system of tests
and the result of applying such an interpretation to the particular
problem of delinquency. The advantage in increased definiteness should
already be evident. When a person is classed as presumably deficient it
will mean that he is in the lowest 0.5% in intellectual development or
within the lowest 1.5%, if he is a persistent delinquent.


Footnote 5:

  Aaron J. Rosanoff. Survey of Mental Disorders in Nassau County, New
  York. Publication No. 9, National Committee for Mental Hygiene, 1917.

Footnote 6:

  Emma O. Lundberg. A Social Study of Mental Defectives in New Castle
  County Delaware. U. S. Dept. of Labor, Children's Bureau, Publication
  No. 24, 1917, pp. 38.

Footnote 7:

  This statement in 1906 seems to be the earliest attempt at a
  quantitative definition of deficiency. As I discovered it after the
  present monograph was practically completed, it furnishes evidence of
  the natural tendency of attempts at more exact definition to take the
  percentage form.

Footnote 8:

  C. Macfie Campbell. The Sub-Normal Child—A Study of the Children in a
  Baltimore School District. Mental Hygiene, 1917, I, 96-147.

Footnote 9:

  Italics mine.

Footnote 10:

  The report of the Massachusetts Commission on Mental Diseases (Vol. I,
  p. 198) shows that social agencies systematically using mental tests
  reported 19.2% as mental cases, while those using examinations only
  for obvious cases reported 1.3%.


Sufficiently large random groups have not been tested with any
development scale to make the determination of the borderline on the
scale more than tentative. Such borderlines must be looked upon as
temporary descriptions to be used in aiding diagnosis until more data
are available. Nevertheless, the percentage method of procedure seems to
be an improvement over other plans of stating the borderline. So far as
the Binet 1908 scale is concerned, when we supplement Goddard's results
with 1500 school children by the data for the lower limits of a random
group of 653 15-year-olds which we tested, the limits on the scale for
passable intellects defined by the percentage method will be found, I
believe, not only more conservative, but more reliable than those in
current use. Moreover the intended meaning of such borders becomes


                  (a) INDICATION FROM A RANDOM GROUP.

The passing limit for adults is unquestionably much more important than
that for children since any child who once passes this limit is assured,
generally speaking, of social fitness so far as intellect is concerned.
He has attained a position intellectually which is sufficiently good to
enable him to get along without social assistance unless he is
especially deficient in will. This borderline for the mature has been so
thoroughly neglected that in none of the common published forms of the
Binet scale, except the new Stanford Scale, is there an attempt to
define it. This seems almost incredible in view of the general use of
the Binet method in diagnosing feeble-mindedness. To be sure, there are
discussions of this upper limit, as we shall see, but they have usually
not been embodied in the actual directions accompanying the scales which
get into the hands of amateurs. Most of these directions content
themselves with describing borderlines for children with no caution
about the final lower limit for social survival.

The borderline for the mature is the first difficulty which a court
examiner will encounter when he attempts to obtain assistance from an
objective system of measurement. Very little experience will convince
one that it is not enough to describe the deficient ability of an adult
in terms of years of retardation. It is widely agreed that at some age
during adolescence practically all the mental processes are available
that will be found in the mature. From that time the advance in ability
is made by attaining greater skill in specific activities through
training and by increasing knowledge, rather than through a native
change in the form of thinking. If mental tests mainly reach capacity
for thinking, as they aim to do, rather than amount of knowledge or
skill in specific work, then we are conservative in using a randomly
selected group at 15 years of age for approximating the borderline on
the scale for the mature.

In connection with the new Stanford Scale, Terman says: “Native
intelligence, in so far as it can be measured by tests now available,
appears to improve but little after the age of 15 or 16 years. It
follows that in calculating the I Q (intelligence quotient) of an adult
subject, it will be necessary to disregard the years he has lived beyond
the point where intelligence attains its final development. Although the
location of this point is not exactly known, it will be sufficiently
accurate for our purpose to assume its location at 16 years” (_57_, p.

Yerkes and Bridges in connection with their Point Scale say, “it seems
highly probable that the adult level is attained as early as the
sixteenth year” (_225_, p. 64). Kuhlmann (_138_) used 15 years as the
divisor in calculating the intelligence quotient of adults and Spearman
thinks that the limit of native development is reached about 15 years
(_184_). He says, “That mental ability reaches its full development
about the period of puberty is still further evidenced by physiology.
For the human brain has been shown to attain its maximum weight between
the ages of 10 and 15 years” (_184_). For the last statement he quotes
Vierordt. On the contrary Wallin thinks that we need more evidence for
the correctness of these hypotheses before choosing a fixed age as a
divisor for adults (_215_, p. 67).

We are not interested in determining a divisor for an adult intelligence
quotient but in fixing a conservative borderline for the mature.
Admitting that the mental capacity of those 15-year-olds at the lower
limit may not be like adults, nevertheless adults would be more likely
to be better than worse. Borderlines for the 15-year-olds, should,
therefore, be safe for adults. Moreover, the lower limits with a truly
random group of 15-year-olds would probably be more reliable than an
assorted group of adults subjectively chosen from different walks in
life and combined in an effort to represent a random mature group. The
Stanford Scale utilizes such combination of selected adults. It seems,
therefore, that we are justified in utilizing the lowest percentages of
randomly selected 15-year-olds as a reasonable criterion for describing
the limits for adult deficiency. Surely adults below this lower limit
for 15-year-olds would have questionable intellectual capacity.

The borderline for the mature being the crucial feature of a
developmental scale when used for detecting feeble-mindedness, it seemed
imperative to us that some effort should be made to obtain records with
a random group of older-age children or adults. Goddard's results with
school children were not significant above eleven years of age since the
personal examinations were confined to children in the sixth grade or
below. The twelve year old group in the sixth grade clearly omits the
best 12-year-olds, so that the percentage method would have no
significance applied to his figures for children above 11 years of age.
Moreover it was obvious that the group of _public school_ children 15
years of age or older would not give a picture of the lower end of a
random group since many children drop out of school at 14. On the
average those that leave are undoubtedly of lower ability than those who

The most valuable data on the borderline for the mature would come from
mental examinations of large random groups of adults. The impossibility
of gaining the consent of adults for such examinations puts this plan
out of consideration. Perhaps the next best method would be to examine
all the children of 15 and 16 years of age in typical communities. It
happened that we could approach this result in Minneapolis since we
there had an excellent school census made from house to house covering
all children under 16 years of age. The Minnesota law requires school
attendance until 16 years of age unless the child has graduated from the
eighth grade. Under the able direction of Mr. D. H. Holbrook of the
attendance department the census of children of school age had been made
with unusual care. All the children living in each elementary school
district in the city were listed in a card index regardless of whether
they were attending public, parochial or private schools, or had been
excused from attendance for disability or for any other reason. Since we
only needed to be sure to examine the lowest few per cent. of the
children in ability this group of 15-year-olds could be tested by
examining all those children in typical school districts in the city who
had not graduated from the eighth grade. A third of the 15-year-olds
were still in the eighth grade or below. Neither the compulsory
attendance law nor the census would have reached the 16-year-old
adequately. In most states even the 15-year-olds would have been above
the compulsory school age.

There were 653 children, (322 boys,) 15 years of age living in the seven
typical districts which were selected objectively for study. Among these
there were 196 who had not graduated from the eighth grade. All of these
latter children were examined, except one who could not be tested as she
was in a hospital on account of illness. Quite a number of the children
were in parochial or private schools, two were followed to the state
industrial school and a number were examined at home. In order to be
sure that we had not missed any institutional cases in these districts
the complete list of Minneapolis children at the State School for
Feeble-Minded was gone through to get any of low ability who might have
been missed.

The seven districts in which the children were to be studied were
chosen, with the idea of avoiding any personal bias in their selection,
by taking them alphabetically by the name of the schools, except that no
district was taken where the normal school attendance of the district
was affected by inadequate school facilities so that children had to be
transferred either to or from that district to other schools in order to
meet crowded conditions. It happened fortunately that none of these
schools represented extreme conditions in the city. The average
percentage of children in the 69 elementary schools of the city retarded
in school position below a standard of 7 years in the first grade, 8 in
the second, etc., was 24.1% with a mean variation of 6.5%. The
percentages retarded in the schools studied were as follows: Adams,
22.7; Bryant, 21.1; Calhoun, 21.7; Corcoran, 29.4; Douglas, 20.4;
Garfield, 18.6; Greeley, 26.4.

Kuhlmann's adaptation of the 1911 scale (_135_) was used as a basis for
the examinations, supplemented by the 1908 scale wherever tests had been
changed so that other forms of the tests were found in either Kuhlmann's
(_136_) or Goddard's (_110_) adaptations of the 1908 scale. Since test
results with the 1908 scale provide the most data for describing the
borderline for the immature, our plan was to use the 1908 form of a test
first when the procedure had changed. The supplementary directions were
arranged for each age so that the testing could proceed methodically and
the results be scored under either the 1908 or 1911 scale with the least
possible disturbance of each test. Over a third of the children were
tested by myself. The rest were tested by three advanced students in
psychology. It is a pleasure to express my thanks to these assistants,
Miss Rita McMullan, Miss Lucile Newcomb and Miss Florence Wells. Besides
having had brief experience in dealing with exceptional children, they
practised testing under my observation until the tests could be given
smoothly and I was convinced of their ability to follow directions
intelligently and make full records with reasonable accuracy. The
results of the tests were all carefully gone over and scored by me. So
far as I can judge, the results are quite as accurate as any other
published tables, although one must always consider the possible effect
of errors of testing. Separate rooms were provided at the schools or
homes so that the child could be alone with the examiner during the

In attempting to define the borderlines on these scales we might either
state the exact scale position in tenths of a year below which 0.5 and
1.5% of the cases fall, or we might merely attempt at present to state
the borderlines in rounded terms of years on the scale. The latter plan
is the one I have adopted for several reasons. The main reason is that I
wish to emphasize that these are still rough boundaries. Besides that,
however, a study of the results shows that the cases do not distribute
by separate tenths of a year so that exactly these percentages could be
picked off, without a questionable smoothing of the curves while the
rounded years approach these limits fairly well.

It seems to me that it is best at present to be carefully conservative
in describing these borderlines, so that I have chosen them from the
available data at the nearest rounded age position which is reasonably
sure not to catch more than these limiting percentages. Throughout the
tables I have also followed the published directions for the 1908 scale
in classing the person in the intellectual age group in which he finally
scores all or all but one of the tests. I recognize, of course, that
this is an arbitrary limit; but it is the limit fixed by the usual
printed directions going with the 1908 scale, which is the only one thus
far standardized for the immature on the percentage basis. For those who
wish to calculate other borderlines or reconstruct the individual tests
of the scale I have provided the complete data for each individual both
for the 1908 and 1911 scales in Table XXI, Appendix I. The table also
gives the exact ages and school grades of each child.

The summary of the results with the tests for those testing under XII is
given in Table III. Life-age[11] at the last birthday and not the
nearest life-age is used in the table. The children were all between
their 15th and 16th birthdays. Following the directions published with
the scales, the basal age for calculating the results in the table is
taken as the highest at which all or all but one test are passed for the
1908 scale, and the highest at which all were passed for the 1911 scale.
Two-tenths is allowed in the table for each test passed above the basal
age and 0.1 for an uncertain answer. The children were tested by the
long method, beginning with the mental-age group at which the child
could pass all the tests and continuing to that age group in which he
failed in all.


    _Percentages of 653 living in these districts, 196 of whom had not
 graduated from the eighth grade and were tested. Scored by the Kuhlmann
      and Goddard 1908 Binet scale and by the Kuhlmann 1911 scale._

                │        1908 Scale         │        1911 Scale
  Scored below  │ Pass all but one in basal │   Pass all in basal age
                │            age            │
                │  Per cent.  │    Cases    │  Per cent.  │    Cases
 IX.0           │          0.0│            0│          0.0│            0
 IX.8           │          0.2│            1│          0.5│            3
 X.0            │          0.3│            2│          0.5│            3
 X.8            │          1.1│            7│          1.2│            8
 XI.0           │          1.2│            8│          2.0│           13
 XI.8           │         10.0│           65│          8.1│           53
 XII.0          │         10.4│           68│         13.0│           85
 XII.8          │         23.6│          153│         29.1│          190
 XIII or XV     │         23.6│          153│         29.7│          194

Thrown into percentages of the group of 653 children living in these
districts, it is evident that a test score of XI raises any person above
the group of intellectual deficients. The percentage that tested this
low, _i. e._, under XI.8, with the 1908 scale, was 10.0 (65 cases) and
this would probably be increased if those who had graduated from the
eighth grade had also been tested. The percentage testing under the same
position in the 1911 scale is 8.1 (53 cases). With the 1911 scale there
were 32 additional cases testing XI.8 or XI.9. The table indicates that
0.2% of the 15-year-olds tested below IX.8 with the 1908 scale, and 0.5%
with the 1911 scale. This defines our scale borderline for the mature
who are presumably deficient as below test-age X. These positions are
near enough to the lowest 0.5%. The group testing of uncertain ability,
age X, (strictly speaking between IX.8 and X.7 inclusive,) includes 0.7
to 0.9%. We thus approach fairly well the rounded age positions which
exclude 1.0% above the lowest 0.5%. The total number testing in
presumably and uncertain groups is thus 1.1%, 7 cases out of 653, for
the 1908 scale and 1.2%, 8 cases, for the 1911 scale. This is to be
compared with the percentage definition that the lowest 1.5% are either
presumably deficient or uncertain.

At present we are entitled to assume that adults testing below XI, _i.
e._, below X.8, are so low in intellectual development that it is a
question whether they have sufficient equipment to survive socially.
Fine discriminations with the Binet scale are not possible with our
present knowledge. So far as our information goes, if we use the
percentage method of defining intellectual deficiency, we may say that
adults who test X are in an uncertain group in intellectual ability,
with the probability that they will require more or less social care,
while those who test IX are deficient enough to need continuous care
unless the evidence of the test is contradicted by other facts or is
accounted for by the existence of removable handicaps.

It is perhaps not necessary to call attention to the fact that X and XI
are used here merely to refer to positions on the Binet scale without
regard to what per cent. of ordinary 10-and-11-year-old children attain
these positions. For example, XI does not imply that most of the
children of eleven years of age are above this borderline. Table IV, to
be given later, suggests that hardly two-thirds of random 12-year-old
children pass this position on the 1908 scale and not half of the
11-year-olds. Thorndike regarded X.8 as normal for a child of 11.6 years
of age. (_200_)

So far as the determination of intellectual deficiency is concerned we
should note with emphasis that placing the limit of passable intellects
at XI for adults almost entirely removes the common objection to the
Binet scale on account of the difficulty of the older age tests. The
older age tests become of little consequence because the best of the
deficient group have a chance at tests in at least two groups above
those of mental age X, so that they can increase their score by passing
advanced tests as they could not if they had to test XII.

As a check upon the borderline for those presumably deficient, it is
important to note that the only case which tested below this borderline
with the 1908 scale was a girl in the 4B grade. She tested exactly IX
with each scale and was the only child in the group who was below the
fifth grade in school. There can be no question that she was mentally
deficient. On the other hand in the group which tested X or above there
are several cases which it would be unjust in my opinion to send to an
institution for the feeble-minded without some other evidence of mental
weakness. Half of them, for example, are in the seventh grade. In
Minneapolis this is not as significant as it might be in other cities,
since pupils are rarely allowed to remain more than two years in the
same grade whether they are able to carry the work of the next higher
grade or not. Pupils in higher grades may not always be able to do even
fifth grade work.

The evidence from the institutions for the feeble-minded indicates that
less than 5% of their inmates test XI or over. Of 1266 examinations at
the Minnesota School for Feeble-Minded, 3.8% (_154_); of 378 examined at
Vineland, 3.2% (_113_); of 140 consecutive admissions examined by Huey
at Illinois, 5.7% (_129_). To be sure, a goodly number of these inmates
are not eleven years of age, but a majority of them are at least that
old and many are older. Of 280 children in the Breslau _Hilfsschulen_,
Chotzen (_89_) found none reaching XI, and only six who tested X. These
few cases in institutions reaching XI or over may well come within our
class of those feeble-minded through volitional deficiency.

Goddard's description of the children at the Vineland school for
feeble-minded who tested XI with the 1908 scale hardly sounds like an
account of social deficiency. He says:

  “In the eleven year old group we find only five individuals, but
  they are children who, for example, can care for the supervisor's
  room entirely, can take care of animals entirely satisfactorily, and
  who require little or no supervision. They are, it is true, not
  quite as expert or trustworthy as those a year older, and yet the
  difference is very little and the two ages can probably be very well
  classed together” (_113_).

The studies of groups are more important for fixing our general rules
than individual examples. We must always expect to find exceptional
cases where the brief intellectual tests given in an hour or less are
not adequate, especially if the testing has been interfered with by the
person's emotional condition at the time or by deliberate deception. A
number of illustrations have been reported of successful adults who have
tested X under careful examinations. Such, for example, are three cases
of successful farmers tested by Wallin (_215_) and a normal school
student tested by Weidensall (_59_). There are two examples of persons
testing IX with the Binet scale and yet earning a living. Such is the
case related by Dr. Glueck of the Italian immigrant making two trips to
this country to accumulate wealth for his family by his labor (_109_),
and the case of the boy reported by Miss Schmidt (_179_). These cases
should make us cautious, but they are so rare that it seems best to
treat those testing IX at least as exceptions.

The group studies confirm our suggestion that a borderline of X or below
will bring in for expert consideration nearly all adults who are
feeble-minded from a lack of intellectual ability, while testing IX is a
fairly clear indication of such serious deficiency as to justify
isolation. That testing X, in the absence of other evidence of conative
disturbance, places the case only in an uncertain region so far as
isolation is concerned is best indicated by the fact that 1.1% to 1.4%
of these 15-year-olds tested this low. We have good evidence that many
in special classes, which contain only about the lowest one per cent.,
afterwards do float in society with or without social assistance. They
cannot be presumed to require isolation, as I showed in the previous
chapter. It is better to say at present that those testing X require
evidence of their deficiency before isolation, except in special
classes, is justified. The test diagnosis alone is too uncertain, even
when there are no removable handicaps.

As to the reliability of these borderlines, too much emphasis can hardly
be put upon the fact that they have been determined for only a single
group of 653 in a single community. They are undoubtedly not the exact
borderlines, although they are the most probable percentage estimates we
have at present and were obtained in a group that was as nearly
unselected as it is possible to obtain. The method of selection was
perfectly objective and excluded no feeble-minded children of this age
living in these school districts.

The theory of sampling applied to percentages (_228_) enables us to say
that the standard deviation of the true lowest 0.5% in samples of this
size made under the same conditions would not be more than 0.28%.[12]
That is to say, if our result were only affected by the size of our
sample the chances are about two out of three that the border of the
true lowest 0.5 per cent. would lie between the border of the lowest
0.22% and the lowest 0.78% of a very large sample. Assuming that the
distribution in this sample represented that of communities generally,
the chances would be two out of three that the true border of the lowest
0.5% for like groups in like communities examined under the same
conditions would lie between IX.0 and X.6 or X.4 on the 1908 and 1911
scales respectively. Moreover, the chances that a case in the lowest
0.5% in this sample would be above the doubtful group in a larger
sample, _i. e._, get above the lowest 1.5%, would be about 1 in 10,000.
On the other hand, the chances that a case above the true lowest 1.5%,
_i. e._, above the uncertain group, would get into the lowest 0.5% in a
larger sample, _i. e._, be classed as clearly deficient intellectually,
would be about 18 in 1,000.

So far as the theory of sampling goes it would seem that these
borderlines for the mature are sufficiently accurate for correcting
present practise. On the other hand, the conditions in Minneapolis so
far as deficiency is concerned are probably better than in the country
as a whole, so that the borderlines here described might very well
exclude more than the lowest 0.5% and 1.5% in the country at large. But
if we shifted the definition so as to exclude the lowest 0.2% and 1.1%
(the percentages empirically found below the limits described), the
borders on the Binet 1908 scale would not be changed from the rough
measures IX and X which are as accurate as we should expect to define
our limits with the present data.


Comparing the suggestions as to the borderline for the mature which have
heretofore been made, we find that they have gradually approached the
boundary now suggested by the percentage method. In 1910 the American
Association for the Study of the Feeble-Minded adopted a tentative
classification in which the upper limit of the feeble-minded included
those “whose mental development does not exceed that of a child of about
twelve years” (_64_). This was based mainly on the fact that Goddard had
found no case at the Vineland school for feeble-minded which tested
higher than XII. Huey later than this found only two such cases at the
institution at Lincoln, Ill., and Kuhlmann only ten cases at the
Minnesota State School for the Feeble-Minded.

There was an early statement by Binet which referred to the practise in
Belgium of regarding older school children as deficient when they were
three years retarded in their school work (_77_, p. 41). This practise
may have also contributed to this formulation by the American
Association. Binet, however, regarded a child of the mentality of twelve
as normal. In 1905, before his tests were arranged in age groups, he

  “Lastly we have noticed that children of twelve years can mostly
  reply to abstract questions. Provisionally we limit mental
  development at this point. A moron shows himself by his inability to
  handle verbal abstractions; he does not understand them sufficiently
  to reply satisfactorily” (_76_, p. 146).

It is important to consider how the suggestion of XII as the upper limit
of feeble-mindedness for adults got into the early practise in this
country as the lower borderline for the mature. It is the most serious
error which has marred investigations in this field. It seems to have
been a case of repeated misunderstanding on the part of examiners for
which nobody in particular was to blame. So far as I can determine
nobody stated directly in connection with any scale what should be
regarded as the lower borderline for the mature. Numerous examiners,
however, in reporting their results, concluded that if the feeble-minded
tested as high as XII then adults who tested XII were feeble-minded.
They were somewhat encouraged in this fallacy by the fact that the 1908
scales suggested three years of retardation as an indication of
feeble-mindedness, and the highest age-group of tests was soon shifted
to fifteen years.

The trouble seems to have been that early workers failed to recognize
that some of the feeble-minded in institutions, the purely conative
cases, have passable capacity so far as the brief intellectual tests are
concerned. To determine scientifically what is the borderline, we should
study randomly selected groups from the general population and determine
the positions on the scale below which practically all are socially
unfit. Or, as Wallin has suggested, we should find out the degree of
tested ability necessary for survival in simple occupations that are
afforded by society (_216_, p. 224). These positions can only be checked
by finding the conditions in institutions or special classes. They
cannot be determined by tests of these abnormal groups alone. Besides
the confusion arising from these feeble-minded who are primarily
unstable or inert, but with passable intellects, reasoning from the
statistics on abnormal groups merely repeats a common fallacy. The fact
that some inmates of institutions test XII does not let us know how many
outside the institutions who test XII actually survive in society.

The randomly selected groups of children on which Binet tried out his
tests were so ridiculously small that he continually cautioned against
adopting his suggestions as to borderlines as anything but tentative.
For judging the borderline for the mature there were no test results
which had not been seriously affected by the methods of selecting the
groups, so we collected the data on this random group of Minneapolis
15-year-olds. I trust that this will make any examiner more careful
about assuming that adults testing XI are clearly unable to survive
socially, unless he is ready to claim that 10% of the general population
are unfit socially.

It is to be noted that, taken literally, the description of the American
Association is not in terms of the Binet scale, but of the mental
development of a normal child of twelve years, although the framers of
the resolution undoubtedly had the Binet scale of mental ages in mind.
It was soon found that the tests for the older ages in the Binet 1908
scale were too difficult for the places assigned them. This is certainly
true with the tests for twelve years and probably with those for eleven.
This evidence is assembled in Table IV. The combined results should be
used only with great caution since the methods of the investigators
differed in detail and the groups were differently chosen. In the groups
of children which Bobertag and Bloch and Preiss tested, there had been
eliminated some of those who were backward in school, while Goddard's
group did not include the best 12-year-olds.

                               TABLE IV.

                            (_1908 Series_)

                │No. of Cases │ Pass tests  │  Pass tests XI or better
                │             │XII or better│
                │  Life-Age   │  Life-Age   │         Life-Ages
  Investigators │  12     11  │     12      │     11      │     12
                │ No.    No.  │ No.     %   │ No.     %   │ No.     %
 Binet and Simon│             │             │             │
 (School in poor│             │             │             │
 quarter)       │             │             │             │
   1908 study   │  11         │  2      18  │             │  7      64
                │         20  │             │  13     65  │
   1911 study   │  23         │             │             │15[13]   65
 Bloch and      │  21         │  21    100  │             │  21    100
 Preiss         │             │             │             │
 (Only pupils up│         15  │             │  13     87  │
 to grade)      │             │             │             │
 Bobertag       │  33         │  19     57  │             │  29     88
 (Pupils        │         34  │             │  18     53  │
 averaged       │             │             │             │
 satisfactory)  │             │             │             │
 Dougherty      │  46         │  9      20  │             │  36     78
 (Includes 8th  │         44  │             │  22     50  │
 grade)         │             │             │             │
 Goddard        │ 144         │  39     27  │             │  75     52
 (Includes none │        166  │             │  73     44  │
 above 6th      │             │             │             │
 grade)         │             │             │             │
 Johnston       │  24         │  6      25  │             │  ?
 (Includes some │         29  │             │  7      24  │
 high school    │             │             │             │
 pupils)        │             │             │             │
 Terman and     │  35         │  3      9   │             │  29     83
 Childs         │             │             │             │
 (Includes a few│         44  │             │  14     32  │
 in 8th grade)  │             │             │             │
 Rogers and     │  20         │  1      5   │             │  5      25
 McIntyre       │             │             │             │
                │         27  │             │  6      22  │
     Totals     │ 357    379  │ 100         │ 166         │ 217?

  Binet and Simon. L'Annee Psychol., 1908, _14_: 1911, _17_: 145-200.
  Bloch and Preiss. Zeits. f. angew. Psychol., 1912, _6_: 539-547.
  Bobertag. Zeits. f. angew. Psychol., 1912, _6_: 495-538.
  Dougherty. J. of Educ. Psychol., 1913, _4_: 338-352.
  Goddard. Ped. Sem., 1911, _18_: 232-259.
  Johnston. J. of Exper. Ped., 1911, _1_: 24-31.
  Terman and Childs. J. of Educ. Psychol., 1912, _3_: (Feb.-May).
  Rogers and McIntyre. Brit. J. of Psychol., 1914, _7_: 265-299.

Each of the studies indicated in the table, except that of Bloch and
Preiss, gives evidence that the XII-year tests are too difficult for
12-year-old children. Moreover, we find that in the 1911 revision of
their scale Binet and Simon advanced their 1908 XII-year tests to
test-age XV and four out of the five XI-year tests to test-age XII.
Passing the XII-year (1908) tests would, therefore, seem to bring a
child above the upper limit of feeble-mindedness as defined even by the
American Association for the Study of Feeble-mindedness, since it means
more than the intelligence of a child of 12.

Goddard still adhered to this borderline of the American Association in
1914 in his work on Feeble-Mindedness. He says: “We have practically
agreed to call all persons feeble-minded who do not arrive at an
intelligence higher than that of the twelve year old normal child” (p.
573). In the same year Schwegler's “Teachers' Manual” for the use of the
Binet scale says that a person who tests XII is a moron if mature
(_180_). Since the evidence of Table IV indicates that 75% of the
twelve-year-olds do not test above XI, even those who adhere to the high
limit of the intelligence of a 12-year-old should have required an adult
to test XI on the Binet scale in order to show deficiency.

In 1911 we find Wallin writing, regarding the 1908 tests, “it is a
question whether the line of feeble-mindedness should not be drawn
between eleven and twelve instead of between twelve and thirteen.... A
number of our twelve-year-olds are certainly very slightly, if at all,
feeble-minded” (_210_). Jennings and Hallock (_31_) and Morrow and
Bridgman (_39_) in testing delinquents reported in 1911 and 1912 that
they regarded those passing the tests for twelve years as socially fit.
Chotzen (_31_) thinks that the two children in his group of pupils from
a _Hilfsschule_ who test ten and are three years or more retarded are
not feeble-minded. Davis thinks that those “showing mentality from ten
to twelve years” may possibly not be called mentally defective (_133_,
p. 187).

In 1915 the editors of the magazine “Ungraded” in their recommendations
regarding the use of the Binet scale say “a mental age of 10 or above is
not necessarily indicative of feeble-mindedness, regardless of how old
the examinee may be” (_66_, p. 7). In the same year Kohs, in reporting
the examinations of 335 consecutive cases at the Chicago House of
Correction, says: “We find normality to range within the limits 12^2 and
10^4 and feeble-mindedness not to extend above the limit 11^2. In other
words, none of our cases testing 11^3 or over was found, with the aid of
other confirmatory data, to be mentally defective. None of our cases
testing 10^3 or below was found to be normal. Of those testing between
10^4 and 11^2, our borderline cases, a little less than half were found
normal, and somewhat more than half were found feeble-minded” (_33_).
His exponents here refer to number of tests and not to tenths of a
test-year. Hinckley (_182_) reports examinations with the Binet 1911
scale on 200 consecutive cases at the New York Clearing House for Mental
Defectives which show that with these suspected cases, which were from
13 to 43 years of age, seven-eighths tested X or below. Referring to
adults, Wallin states that he has “provisionally placed the limen
somewhere between the ages of IX and X” (_215_). Dr. Mabel Fernald at
the Bedford Reformatory laboratory said in 1917, “many of us for some
time have been using a standard that only those who rank below ten years
mentally can be called feeble-minded with certainty” (_16_). The reader
should also see the admirable review and discussion of the borderlines
on the Binet scale in Chap. II of Wallin's _Problems of Subnormality_.
Two descriptions of the scale borderlines in books on mental testing
which appeared in 1917 are of interest. In his _Clinical Studies in
Feeble-Mindedness_ (p. 76), E. A. Doll says:

  “By the Binet-Simon method feeble-mindedness is almost always
  (probably more than 95 times in a hundred) an accurately safe
  diagnosis when the person examined exhibits a mental age under 12
  years with an absolute retardation of more than three years, or a
  relative retardation of more than 25 per cent.”

N. J. Melville, in his _Standard Method of Testing Juvenile Mentality_
(p. 10), says:

  “Conservative estimates today place the upper limit of
  feeble-mindedness at least in a legal sense at Binet age ten; others
  place it at Binet age eleven.... A Binet age score below eleven when
  accompanied by a sub-age (retardation) of more than three years is
  usually indicative of serious mental deficiency. Even when
  accompanied by a slight sub-age score, a Binet age score below
  eleven may be indicative of potential mental deficiency when the
  test record reveals a Binet base that is six or more years below the
  life age.”

In 1916 the new Stanford scale appeared and its tests are arranged so
that approximately 50% of each age instead of 75%, test at age or above.
Even with this lowering of the scale units, Dr. Terman describes his
borderline for “definite feeble-mindedness” as below an intelligence
quotient of 70. This would mean for his 16-year-old mature borderline a
mental age on this scale of XI.2. We have no means of determining to
what positions these points on the Stanford scale would correspond on
the 1908 or 1911 Binet scales. Dr. Terman says “the adult moron would
range from about 7-year to 11-year intelligence” (_57_). Apparently also
referring to the Stanford scale, the physicians at the Pediatric Clinic
of that university agree with this borderline and say: “morons are such
high grade feeble-minded as never at any age acquire a mental age
greater than 10 years” (_169_). That there is still need for more
caution is evidenced by the statement of a prominent clinician in 1916
that “cases prove ultimately to be feeble-minded since they never
develop beyond 12 years intelligence” (_135_).

Most interesting perhaps is the fact that Binet and Simon themselves,
the collaborators who first formulated the scale for measuring
intelligence by mental ages, after their years of experience with the
tests came, by rule of thumb, to regard IX as the highest level reached
by those testing deficient. Dr. Simon stated the borderline for the
mature in this way in a paper read in England in 1914 and published the
next year. He said:

  “Provisionally it might be proposed to fix at 9 years the upper
  level of mental debility.... We have reason to think that a
  development equivalent to the normal average at 9 years of age is
  the minimum below which the individual is incapable of getting along
  without tutelage in the conditions of modern life. A certain number
  of facts suggest this view and are mutually confirmatory. Nine years
  is the intellectual level found in the lowest class of domestic
  servants, in those who are just on the border of a possible
  existence in economic independence; it is, on the other hand, the
  highest level met with in general paralytics who come under asylum
  care on account of their dementia; so long as a general paralytic,
  setting aside any question of active delirious symptoms, has not
  fallen below the intellectual level of 9 years, he can keep at
  liberty; once he has reached that level, he ceases to be able to
  live in society. And lastly, when we examine in our asylums cases of
  congenital defect, brought under care for the sole reason that their
  intelligence would not admit of their adapting themselves
  sufficiently to the complex conditions of life, we find that amongst
  the most highly developed the level of intelligence does not exceed
  that of a normal child of 9 years of age” (_182_).

In connection with their 1911 revision of the scale Binet and Simon had
stated that among 20 adults in a hospital where custodial care was
provided for the deficient “we found that the best endowed did not
surpass the normal level of nine or ten years, and in consequence our
measuring scale furnished us something by which to raise before them a
barrier that they could not pass” (_79_, p. 267). They, however, then
expressed complete reserve as to the application of this criterion to
subjects in different environments on their presumption that deficiency
for the laboring class is different from that for other classes in the

The Germans seem to have early recognized a lower borderline for the
mature than we did in this country for we find Chotzen saying in 1912
that he agreed with Binet's finding that “idiots do not rise above a
mental age of three, imbeciles not over seven, and debile not over ten”
(_89_, p. 494). Stern also quotes Binet as declaring that the moron does
not progress beyond the mental age of nine (_188_, p. 70).

The tendency of interpretation indicated by these studies is plainly to
lower the borderline for passable mature intellects until it approaches
the limits which the percentage definition suggests as reasonable from
our available evidence. The percentage plan thus confirms the borderline
that has been approached gradually by hit or miss methods. An adult
testing IX is presumed deficient, while one testing X is in an uncertain
zone. The numerous studies of delinquents which have regarded adults who
tested XI and even XII as deficient have seriously overestimated the
problem of the deficient delinquent, as we shall see in our later
chapter on tested delinquents.


                     (a) FOR THE BINET 1908 SCALE.

In attempting to adapt the percentage method of description to the
border region for the immature, it is essential that the tests shall
have been tried out on randomly selected groups. Neither teachers nor
the examiner should pick out children to be tested, if we are to know
much about the region of lowest intellects. While Bobertag's method of
choosing typical groups by balancing those backward in school by those
advanced, is serviceable for his purpose of determining norms, the
personal element of choice involved makes the results thus obtained
almost useless in determining the lower limit of ability.

In regard to the diagnosis of intellectual deficiency by the Binet 1908
or 1911 scales, we know much more about the interpretation of results
obtained with the 1908 scale than with the 1911 scale. The 1908 scale
was therefore used for our examinations of juvenile delinquents. The
best available data on which to base a description of the borderline for
the immature is that collected by Goddard (_119_). He says that he
“arranged to test the entire school population of one complete school
system. This system includes about five thousand population within a
small city and as many more outside, so that we have, city and country,
a school population of about two thousand children.... In the seventh
and eighth grammar grades and the high school, the children were tested
in groups.” Since only the first six grades were tested individually and
only these results are published in sufficient detail to be available,
we shall confine this account to the school children below the seventh
grade. It must be remembered that any children of the idiot class and
possibly some of the low imbeciles would not be included in his figures
for they would probably have been excused from school attendance. In a
small rural community it is not likely that these would be numerous
enough to change the rough borderline materially. We thus have a fairly
random group for a small town and its environs.

Since we cannot use Goddard's results for our purpose above the sixth
grade, it is plain that we would not sufficiently approach a random
distribution for any age above 11 years. In Minneapolis, for example, a
recent census showed 28% of the public school children 12 years of age
are in the seventh grade or above, while 6% of the better
eleven-year-olds would be excluded by including only those below the
seventh grade. We have therefore omitted from our calculations all of
Goddard's results for children above eleven years of age as too
unreliable for purposes of percentage estimations. Even his
eleven-year-olds may be affected.

Although it is not clear in the published reports whether the nearest or
last birthday was used, Dr. Goddard has informed me that his table shows
the results for ages at the last birthday. A child is regarded as six
until he has reached his seventh birthday, as is customary. Throughout
this book I have followed this method of using age to mean age at last
birthday, or _avowed age_. This is in conformity with the common use of
age and with general anthropometric practise. It is less confusing and
less subject to mistake or errors of record. On the whole, I believe
that in statistical work avowed age is preferable to nearest age.

                                TABLE V.

                    SCALE. (_From Goddard's Table._)

            │           │                Years Retarded
  Life-Age  │  No. of   │Two or more║  Three or │  Four or  │  Five or
            │   cases   │           ║    more   │    more   │   more
           5│        114│        5.3║        1.8│        ...│        ...
           6│        160│        2.5║        0.6│        0.6│        ...
           7│        197│        5.6║        1.5│        0.5│        0.0
           8│        209│        2.4║        1.9│        1.0│        0.0
           9│        201│        1.3║        0.0│        0.0│        0.0
            │           │           ╟═══════════╢           │
          10│        222│       18.9│        8.1║        1.4│        0.0
          11│        166│       25.9│       10.8║        3.0│        0.6
            │       ————│           │           ║           │
            │       1269│           │           ║           │

In the accompanying Table V Goddard's results are arranged so as to show
the percentages at each life-age retarded two or more, three or more,
four or more, and five or more years according to the Binet 1908 scale.
The heavy black line indicates the upper borderline of the doubtful
group according to our interpretation. In spite of irregularities, due
mainly to insufficient numbers, the trend of the table is fairly plain.
The column of percentages two or more years retarded and to the left of
the heavy line suggests that the break comes at ten years of age. Using
our tentative criterion of 0.5% presumably deficient and the next 1.0%
uncertain intellectually, the outcome of this analysis is a rather
striking demonstration of the feasibility of the percentage procedure
even when the groups examined at each age are only composed of about 200
cases. I have preferred to take the empirical data at the lower extreme
of each age distribution instead of projecting the tail of a smoothed
distribution curve for each age.

Until better data are available we have adopted in practise, as a result
of the study of this table, the procedure of considering any child who
is ten years of age or over as testing of doubtful capacity if he is
four or more years retarded below his chronological age, three or more
years retarded if he is under ten years of age. If he shows one
additional year of retardation we consider, in the absence of some other
explanation of his retardation, that he is presumably intellectually
deficient enough to justify a recommendation of isolation. Of course no
such recommendation should be made without a complete medical
examination, a full knowledge of the history of the case and a checking
of the record by further tests at different times when there is any
suspicion that the child has not done as well as he might under other

The fact that we have no data on random groups 12, 13 and 14 years of
age leaves a gap which may mean that our criterion of 5 years
retardation for presumable deficiency at these ages is too small. It is
possible that the shift to 6 years retardation should be made before 15
years, which is the position where our criterion for the borderline for
the mature automatically makes the shift. We say a 15-year-old testing X
is above the group presumably deficient as he has entered the “doubtful”
adult class.

It is also to be remembered that the standard error expected from the
results of samples as small as these is 0.5% when the sample is 200 and
0.7% when it is 100. The limits thus might easily shift a year. The
suggested borderlines for the immature can at best be regarded only as
the most likely under the meager evidence available.

Whether the borderlines for deficiency on the Binet scale should be
described in terms of years of retardation is doubtful except, as in
this case, for practical convenience. It is certainly only a rough
indication of the borderlines. When this method has not been followed
the most common practise is to use some form of Stern's “intelligence
quotient.” An extended discussion of this question is reserved for Part
II of this book, to which the reader is referred. It need only be said
here that the percentage procedure adapts itself to either method of
description. Since the designation of the limits must be very rough
until we have much further information from tests upon unselected
groups, we have adopted the common method of description in terms of
years of retardation, since it seems to afford for the 1908 scale the
simplest expression of the borderline until the tests have been much
improved. It happens that the empirical results for 5 years of age and
over lend themselves to designating the lowest percentages in terms of
years of retardation with only a single shift at 9 years of age. An
equally accurate designation by the intelligence quotient would be quite
complicated if it were adapted equally well to the different life-ages.

The fact that the Binet mental ages do not signify corresponding norms
at each age has been frequently pointed out (_200_). Moreover it is
probable that one year of retardation on the scale means a different
thing at different chronological ages. With the new Stanford form of the
scale, for example, “a year of deviation at age 6 is exactly equivalent
to a deviation of 18 months at age 9, and to 2 years at age 12, etc.”
(_197_) when measured in terms of the deviation in ability at these
ages. This variation does not interfere, however, with our use of the
“years of retardation” merely as a short method for describing
empirically the positions on the scale which roughly and conservatively
designate the same percentages of children of low ability at various
ages. Besides its convenience in this respect, there is no question but
that such a description does help better than a quotient to convince the
public of the seriousness of the deficiency.

A more serious theoretical objection to describing the borderline for
the immature in terms of years of retardation is that, when one changes
from three to four years of retardation, it is clear that a moron who
tests VI at 9 years of age would be supposed to be still only VI at 10
years in order to remain below the borderline, while it is known that
there is some, albeit a small, amount of progress made by the higher
class deficients at these ages. In the crude state in which the Binet
scale still remains, however, we have preferred to waive these
theoretical objections in favor of the prevalent custom which has the
advantages of simplicity, practical convenience, popular significance
and, in this case, equal accuracy.

It is, of course, very desirable that the results obtained by Goddard as
well as our Minneapolis results should be checked by data on unselected
groups elsewhere. With the 1908 scale the only other data which seems
fairly to represent a random selection are those of Terman and Child's
(_195_, p. 69). Since they examined less than 50 at any age, however,
their table helps only to check roughly the borderline suggested. The
percentages retarded two years or more changed to the basis of
calculation we used, indicate that the break comes at 10 years. The
percentages from six up to ten years run 0, 3, 7, 6, when they change to
12% or more for the following ages. While the groups are too small to
indicate the borderlines for each age, yet, when we group the children
from 6-9 years inclusive, under our interpretation we find that a year
less than our upper borderline for the uncertain group would give 4.8%
of 147 cases. With 142 cases in the group 10, 11, and 12 years old, 5.6%
would be caught by placing the borderline for the doubtful a year less
than we have indicated. Our scale borderlines are thus in harmony with
these data.


When we turn to data from randomly selected groups for judging the
borderlines with other developmental scales than the 1908 Binet, we find
that a group of children in the rural schools of Porter County, Indiana,
have been examined with the Goddard adaptation of the Binet 1911 scale
(_92_) and a group of school children in a Minnesota city, with the
Kuhlmann adaptation of the 1911 scale (_138_). The important results
with each study are given in Table VI. In the Indiana study the children
were examined through the eighth grade. The elimination of older
children from school would certainly affect the groups over 13 years of
age and probably disturb the results even for the 13-year olds. For this
group the results are published only for nearest mental and nearest
life-ages. The results are, therefore, not strictly comparable with
those of Table V. for the 1908 scale. It is doubtful whether tests on
children in the rural schools should be used for indicating borderlines.
The table suggests, however, that the borderlines we have indicated for
the 1908 scale are not too conservative for the immature tested with the
1911 scale. It is possible, however, that with Goddard's adaptation the
break comes at 9 years of age instead of 10.

                                TABLE VI.


  _Children in the Rural Schools of Porter County, Indiana, tested with
 the Goddard 1911 scale. (From Table XIII, U. S. Public Health Bulletin,
                                 No. 77)_

   Nearest  │   Total   │Percentages showing the following years of
  Life-Ages │  Pupils   │tested retardation according to the nearest
            │           │mental ages:
            │           │Two or more│ Three or  │  Four or  │  Five or
            │           │           │   more    │   more    │   more
           6│        107│        2.8│           │           │
           7│        232│       6.03│        .43│           │
           8│        234│       8.12│       2.12│        .42│
           9│        216│      12.04│       5.54│       1.84│        .92
          10│        278│      19.88│       3.58│       1.08│        .36
          11│        212│       18.3│        8.4│        1.8│
          12│        243│       33.9│       12.9│        2.6│
          13│        249│       63.7│       27.9│        8.4│        2.8

 _Number of Pupils Testing retarded according to Kuhlmann's revision of
          the Binet 1911 scale. (From Kuhlmann's Table VIII.)_

               │              │       Exact years of retardation.
    Nearest    │ Total Pupils │  1 or more  │  2 or more  │  3 or more
    Life-Age   │              │             │             │
              6│            38│            0│            0│            0
              7│            82│            4│            0│            0
              8│            95│            9│            0│            0
              9│            91│           12│            2│            0
             10│            84│           16│            9│            1
             11│            88│           18│            4│            0
             12│            75│           32│            8│            1

Kuhlmann, with the assistance of twenty teachers whom he started in the
work and whom he regards as “untrained examiners,” measured “the public
school children from the first to the seventh grade, inclusive, in a
Minnesota city.” The essential figures from his results are given in
Table VI. These results are not directly comparable with those of
Goddard using the 1908 scale, since Kuhlmann tabulates the nearest ages
instead of the actual ages. His age groups would therefore average a
half year younger chronologically than Goddard's. Moreover, the exact
amount of retardation to tenths of a year was then calculated from the
exact age, and it is to be remembered that the method of calculating the
mental age was changed in 1911 so as to start with a basal age in which
all tests were passed. The effect of these changes would be that some of
those recorded in Kuhlmann's table as two years retarded might easily be
a year more retarded under the same methods of calculation that were
previously used. Using his method of computation, it is clear that the
general borderline for the immature with this scale would not be as low
as we have indicated for the 1908 Binet scale. It would apparently be
about a year less, _i. e._, two years of retardation for those six to
nine years of age, and three years retardation for those 10 or above in
order to fall within our doubtful group. The 13 year old group are not
included here. They would not be even approximately random since those
who had reached the eighth grade or above were not examined. It is
interesting to note that the break in frequency of serious retardation
again occurs in the change from those chronologically 9 years of age to
those 10 years of age.

The Stanford Revision and Extension of the Binet-Simon Scale (_57_) has
included a percentage designation of the degrees of ability by a
classification of intelligence quotients (I Q's). It is interesting to
find the percentage method of setting forth the borderlines is utilized
to supplement the intelligence quotients in this important revision of
the Binet-Simon Scale. It shows how the method may be adapted to testing
of intelligence quotients. For fixing the borderline for the immature
the Stanford scale affords the best means provided by any of the
revisions or adaptations of the Binet scale. The amount of data on
randomly selected groups of school children, by which these borderlines
were determined, is, however, less than with the 1908 Binet Scale as
given by Goddard and summarized in our Table V. The Stanford Scale was
standardized for the immature by testing 80 to 120 native born school
children at each age from 5 to 14 inclusive, a total of 905. While the
1908 scale gives corresponding distributions for 114 to 222 children at
each age from 5 to 11 inclusive, a total of 1269. Using the I Q's
adopted by Dr. Terman for the Stanford Scale, the lowest 1% of the
children were found to reach only an I Q of 70 or below, 2% to reach 73
or below, 5% to reach 78 or below. The author designates below 70 as
“definite feeble-mindedness,” 70-80 as “borderline deficiency, sometimes
classified as dullness, often as feeble-mindedness.” His “definite
feeble-mindedness” thus includes somewhat fewer than our “presumably
deficient” and “uncertain groups” combined. The distribution of the
intelligence quotients was “found fairly symmetrical at each age from 5
to 14.” The range including the middle 50% of the I Q's, was found
practically constant (_57_, p. 66). The data for the extreme cases have
not been published except for ages 6, 9 and 13. For these ages 1% were
75 or below at 6 years, 2% at nine years, and 7% at 13 (_197_). The
results with the extreme cases at each age are the most important factor
in fixing the borderline. The combined per cent. results with I Q of 905
children at different ages, which show 0.33% testing 65 or below and
2.3% 75 or below, may be deceptive for separate ages.

It seems clear that the criterion for tested deficiency suggested by our
study is more conservative than that of the Stanford scale which says:

  “All who test below 70 I Q by the Stanford revision of the
  Binet-Simon Scale should be considered feeble-minded, and it is an
  open question whether it would not be justifiable to consider 75 I Q
  as the lower limit of “normal” intelligence. Certainly a large
  proportion falling between 70 and 75 can hardly be classed as other
  than feeble-minded, even according to the social criterion.” (_57_,
  p. 81)

In regard to the borderline for the mature with the Stanford scale it is
especially important to note that at present no randomly selected mature
group has been tested with this scale so that we are at a loss to know
what would be a safe borderline for adults with it. It is peculiarly
unsafe, it seems to me, to carry over an intelligence quotient which may
shut out the lowest 1% of children who distribute normally, to the
uncertain borderline of an adult group composed of thirty business men,
150 migrating unemployed, 150 adolescent delinquents and 50 high school
students. By these data it would be impossible to tell what per cent. of
a random group of adults would be shut out by this borderline of 70.


 The lower range of “intelligence coefficients” for the normal group of
              school children and adults (226, Table III).

 Nearest Ages   │  4-5  │  6-7  │  8-9  │ 10-11 │ 12-13 │ 14-15 │ 18-on
 No. of Cases   │  84   │  357  │  196  │  161  │  120  │  77   │  284
 Presumably     │       │ Under │       │ Under │       │       │ Under
   deficient    │       │  .61  │       │  .61  │       │       │  .61
                │       │ 0.4%  │       │ 0.6%  │       │       │ 0.7%
 Doubtful       │ Under │.61 to │ Under │.61 to │ Under │ Under │.61 to
                │  .51  │  .81  │  .51  │  .71  │  .51  │  .61  │  .71
 Both           │(4.8%) │ 1.5%  │ 1.5%  │(5.0%) │ 1.7%  │ 1.3%  │(6.3%)

     Pupils of Grammar School B, Cambridge, Mass. (225, Table III)

 Ages           │  6   │  7   │  8   │  9   │  10  │  11  │  12  │  13
 No. of Pupils  │  71  │  73  │  61  │  71  │  76  │  79  │  60  │  52
 Per Cent of    │ 1.4  │ 1.4  │ 1.5  │ 2.7  │ 1.3  │ 1.3  │ 1.7  │ 2.0
   Pupils at    │      │      │      │      │      │      │      │
 and Below      │  11  │  14  │  15  │  21  │  35  │  40  │  33  │  38
   Points       │      │      │      │      │      │      │      │

For the Point Scale for Measuring Mental Ability, prepared by Yerkes,
Bridges and Hardwick, we have two sets of data which give the only
empirical basis for estimating the percentage borderlines for the
various ages (_225_, _226_). These data are restated in terms of
percents in Table VII. The first part of the table shows the borderline
results with the normal group composed of 829 pupils of the Cambridge
schools, 166 pupils of Iowa schools, 237 in the group of Cincinnati
18-year-old working girls and an adult Massachusetts group of 50. The
table illustrates how difficult it is to find a common borderline in
terms of a ratio, in this case the “coefficient of intelligence,” for a
series of life-ages. It certainly seems hazardous to attempt to smooth
these empirical borderlines for the different ages by accepting, on the
present evidence, the suggestion of the authors that a coefficient of
.50 or less at any of these ages indicates the individual is “dependent”
and coefficients from .51-70 that he is “inferior,” since the data show
the lowest group would include only the lowest 0.04% of 18 years of age
and over, while it includes 4.8% of those in their table four and five
years of age. Indeed, the authors note that “a few months' difference in
age will alter the coefficient of a five or six year old child by ten to
thirty per cent.” Under such circumstances it would be better for the
present to use the empirical basis suggested from the data of Table VII
rather than to attempt to use a uniform borderline coefficient for the
various ages. For calculating the coefficient of a particular
individual, his point scale record should presumably be divided by the
revised norms published by the authors, which are as follows for the
nearest life-ages, reading the dots on their graph: 4 yrs. 15 points, 5
yrs. 22, 6 yrs. 28, 7 yrs. 35, 8 yrs. 41, 9 yrs. 50, 10 yrs. 58, 11 yrs.
64, 12 yrs. 70, 13 yrs. 74, 14 yrs. 79, 15 yrs. 81, 16 yrs. 84, 17 yrs.
86, 18 yrs. 88.

Since all the pupils in Grammar School B, who were not absent during the
periods of examination, were examined, the distribution of these 675
pupils may be serviceable for obtaining a rough idea of the borderlines
in terms of points at the different ages from 6-13 inclusive. These
individuals “constituted the population of a city grammar school in a
medium to poor region and including grades from the kindergarten to the
eighth, inclusive.” On account of the small number of individuals at
each age the errors are large and the limits should be used only with
much caution as an indication of the general trend of the table.

All the scales, it should be noted, have been tried out on immature
groups composed only of school children. These would not include those
children who are so deficient as not to be sent to school. The
borderlines determined with school children, therefore, tend to shut out
a slightly larger percentage of all children than of school children.
They would, therefore, tend to class slightly too many as deficient.
Moreover, the groups tested were probably in communities which are
somewhat above the average in ability so that we should be doubly
cautious in using the borderlines for the immature.


The confusion over the amount of allowable retardation in evaluating the
results of Binet tests is illustrated by the variations in practise. In
1908 Binet and Simon said: “On the contrary, a retardation of two years
is rare enough; ... Let us admit that every time it occurs, the question
may be raised as to whether the child is subnormal, and in what category
he should be placed” (_79_, p. 269). In 1911 they had become much more
conservative. With their new scale they stated: “We would add that a
child should not be considered defective in intelligence no matter how
little he knows unless his retardation of intelligence amounts to more
than two years” (_78_). This cautious statement seems to have been
converted by the various translators into a rule that every child
retarded three years was to be regarded deficient. Drummond, for
example, in his translation says: “Should a child's mental age show a
retardation of three years as compared with his chronological age, and
should there be no evident explanation of this, such as ill health,
neglect of school attendance, etc., he is reckoned as deficient
mentally” (_77_, p. 163). Wallin, however, in 1911 kept to the original
conservative statement, “children retarded less than three years should
probably not be rated as feeble-minded” (_211_, p. 16).

In his book on Mentally Defective Children, before the 1908 scale had
appeared, Binet had adopted the Belgian practise of making a distinction
between younger and older children as to the amounts of allowable
_school_ retardation before the question of mental deficiency should be
raised. As a method of preliminary selection for examination he used a
retardation in school position of two years when the child was under 9
years of age and three years when he had passed his ninth birthday
(_77_, p. 42). This practise was carried over into the field of mental
tests, and Huey then qualified these limits by the safer allowance of
four and three years of tested retardation with the change still at nine
years (_129_).

The German standard, formulated by Bobertag and accepted by Chotzen
(_89_, p. 494), is to place the lower limit for the normal as less than
three years retardation at ten years of age or less than two years
retardation under that age. The change in the amount of retardation
allowed came at the same position we advocated instead of at 9 as was
earlier suggested.

The early practise in the United States was merely to regard three years
retardation as the sign of feeble-mindedness. This custom was even
followed in 1914 for all under 16 years of age by Mrs. Streeter in the
investigation by the New Hampshire Children's Commission of Institutions
in that state. She did not call any feeble-minded who tested over XII
(_40_, p. 79). In both the 1908 and 1911 editions of the Binet scale
issued by Goddard, he stated that if a child “is more than three years
backward he is mentally defective,” giving no caution about a borderline
for the mature. This is a practise which has been followed so far as the
immature are concerned, by Goddard's students generally. Kuhlmann
carefully avoids the statement of a borderline with both his 1908 and
1911 adaptations of the Binet scale, but he has since advocated using an
intelligence quotient of less than .75 with his 1911 scale to indicate
feeble-mindedness and leaving a doubtful area from .75 to .80 (_140_).
Stern suggested a borderline of .80 with the intelligence quotient
(_188_). Even a quotient of .75 would call a child feeble-minded by
Kuhlmann's 1911 scale if he tested two years retarded at eight and three
years retarded at twelve. Haines suggests using, with caution, a
borderline with a modified Point Scale which should be at 75% of the
average performance measured in points at each age for individuals over
thirteen years, and four years retardation for 13 years and younger

Pintner and Paterson collected in one table the test results with the
Binet scale published by thirteen different investigators and covering
4,429 children tested (_44_, p. 49). They do not attempt to readjust
these results so as to allow for the very great differences in the
methods by which the different groups were chosen to be tested or the
different uses of actual life-age and nearest life-age. Such a table is,
as they recognize, too hazardous to use for determining the borderlines
of deficiency. There might be an average difference of at least a year
in the mental ages obtained by different investigators when no allowance
is made for their different procedures. Nevertheless, it is interesting
to note that a mental quotient of .75 is less conservative than the
lowest 3% which is the borderline of feeble-mindedness that they
suggest. The lowest 3% they find would include, for example, those who
were 1.5 years or more retarded at age 5, 2.1 years retarded at 9 and
2.8 years at age 10.

The most important confirmation of the claim that a borderline for the
immature should require at least 4 years retardation comes from the
Galton biometric laboratory in London. Karl Pearson has furnished a
careful statistical treatment of Jaederholm's results in testing all the
301 children in special classes in Stockholm compared with 261 normal
children in the same schools. Pearson found that the modified 1911 Binet
scale which Jaederholm used could be corrected so that the normal
children at each age averaged very closely to their age norms from 7 to
14 years of age. Under these conditions of the scale he generalized on
the basis of the children in the Stockholm special classes who were from
7 to 15 years of age, as follows:

  “The reader may rest assured that until the mental age of a child is
  something like four years in arrear of its physical age it is not
  possible to dogmatically assert, on the basis of the most scientific
  test yet proposed as a measure of intelligence, that it is
  feeble-minded. Even then all we can say is that such a child would
  be unlikely to occur once in 261 normal children, or occurs under ½%
  in the normal child population.” (_167_, p. 18).

In a later paper he says that those children “from 4 to 4.5 years and
beyond of mental defect could not be matched at all from 27,000
children,” on the assumption of a normal distribution fitted to the
normal Stockholm school children (_164_, p. 51). He says further:

  “It is a matter of purely practical convenience where the
  division—if there must be an arbitrary one—between the normal and
  defective child is placed; we suggest that it be placed at either 3
  or 4 years of mental defect. But as mental defect increases with the
  age of the mentally defective the division will be really a function
  of the child's age” (_167_, p. 37).

Since he finds the children in the special classes fall further behind
the normal children on the average 4 months each year of life, this
means that 3 years retardation at 7 years of age would be equivalent to
4 years at 10.

In spite of uncertainty introduced by the use of quotients, the general
tendency in interpretation of results with Binet scales has thus been to
make a distinction in the amount of retardation signifying deficiency
among younger and older children and to require four years retardation,
at least for the older ages. Our criterion for the borderline of three
years retardation for children under 10 years and four years for 10
years and over, with an extra year to be quite sure that the deficiency
is sufficient to justify isolation, seems to be in line with the best
practise at present among those who have had much experience with the
Binet scale. Fortunately, little harm has been done to the individuals
themselves by this uncertainty in the interpretation of the scores with
the scale, since only questionable cases have been affected. These have
generally been diagnosed, before disposing of the child, by some expert
who understands the sources of error in mental tests. On the other hand,
shifting the limit of allowable retardation by one year makes a great
difference in the estimation of the frequency of feeble-mindedness in
particular groups, as will be shown in our discussion of deficient


Footnote 11:

  Throughout this study I shall use the literal translation of the
  German term “lebensalter,” life-age, instead of the awkward
  “chronological age.”

Footnote 12:

  _S. E._ = √(_p._ _q._/_n_)

Footnote 13:

  Tests XI were recorded as XII in the 1911 series.



We are now in a position to evaluate the Binet examinations of
delinquents. Let us first note our results for a group of 123
consecutive cases at the Hennepin County Detention Home.[14] It is not a
detention home in the sense of a place where children are held awaiting
the disposition of their cases by the Juvenile Court. It is better
described by its unofficial title, The Glen Lake Farm School for Boys.
This county training school for delinquents is located on a splendid
farm beside a small lake fourteen miles outside of Minneapolis. The boys
are sent there by the juvenile court for a few months' training as an
intermediate discipline between probation and sentence to the State
School at Redwing.

The character of this group of 123 randomly selected delinquents is
further indicated by the fact that 69 of them had already been brought
into court two or more times, 54 were first offenders. Boys are sent to
Glen Lake whenever the nature of their delinquency or the conditions at
home, together with the personality of the boy, seem to the court to
require this special training. A summary of the offenses for which the
boys were brought into court does not, therefore, show the character of
the boy as it is known to the court through the evidence and the
efficient service of the probation officers. It shows, however, that the
last offenses for which this group were being disciplined were as
follows: Petit larceny 29, truancy 25, incorrigibility 25, burglary 9,
grand larceny 6, disorderly conduct 4, malicious destruction of property
4, trespass 3, sweeping grain cars 3, breaking and entering 3, indecent
conduct 2, miscellaneous offenses one each 8, total 123. Perhaps a more
important indication of the character of the offenders in this group is
that they represent about a quarter of the cases brought before the
juvenile court during the period of this study, a little over a year.
With the exception of a very few cases sent directly to the State
Industrial School they may thus be regarded as typically the worst
quarter of the delinquent boys under 17 years of age in Minneapolis.

The majority of boys were tested by myself after several year's
experience with the clinic in mental development at the University of
Minnesota and after examining many other delinquents. Some were tested
by assistants from the university clinic, Mrs. Marie C. Nehls and Mr.
Harold D. Kitson, who had been specially trained for this. Their
detailed reports were carefully gone over and evaluated. The Binet 1908
series (_136_) was used, except that for tests above XII either tests
XIII were used, or later these were supplemented by two other tests,
which have been placed in the age XV group or adult groups, in the
revisions of the Binet scale published by Goddard (_110_) or Kuhlmann
(_135_). This variation was of small importance since a boy was regarded
as of passable intellect if he scored X.8. We always gave the three
tests of the XIII group and the boy was credited with age XIII if he
passed two out of the original XIII year tests or four out of five tests
given above XII. In accordance with our conservative position the rule
of this 1908 scale for scoring was followed and the boy credited with
the highest age for which he passed all but one test, plus one year for
each five higher tests passed. This is the basis of the 1908 form of the
scale as standardized by Goddard. Appendix II gives the detailed results
for each boy with exact life-age and tenths of test-age on the scale,
basal test-age with the tests, grade in school at the first of September
when he was of this life-age and offense for which he was being
disciplined. It also indicates which boys were repeaters. The results of
this table are summarized in Tables VIII and IX. The life-ages at the
last birthday are used rather than the nearest ages, since this accords
with Goddard's standardization and with the common use of the term
“age.” Moreover it seems to conform to the best practise and to be less
likely to lead to mistakes. Table IX also shows the school position of
each boy. Since a number of the older boys had left school, in order to
tabulate their school positions in reference to their life-ages it was
necessary to assume that they would have continued to progress normally
from the position they held when they left. The Minnesota law requires
attendance at school until sixteen years of age unless before that the
child graduates from the eighth grade. In this group most of those
sixteen years of age and a goodly number of those fifteen years old had
left school, so that their school position had to be advanced a year in
the table; a very few of the 16-year-olds had to be advanced two years
in the table. In all cases the school position is given relative to the
first of September when the boy was of the life-age given. Either ages
six or seven are taken as satisfactory for the first grade, ages seven
or eight for the second grade, and so on with the other grades.

                              TABLE VIII.


          │                 Life-Ages at Last Birthday
 Test-Ages│   6│   7│   8│   9│  10│  11│  12│  13│  14│  15│  16│Totals
 VII      │    │   1│    │    │    │    │    │    │    │    │    │     1
 VIII     │   1│    │    │    │   1│    │    │   1│    │    │    │     3
 IX       │    │    │    │   4│   2│   1│    │   1│    │    │   1│     8
 X        │    │    │    │   1│   2│   2│   1│   5│   2│   3│   1│    17
 XI       │    │    │    │   1│   2│   8│   6│   9│   6│  13│   3│    48
 XII      │    │    │    │    │   1│   2│   5│   4│   6│   7│   3│    27
 XIII     │    │    │    │    │    │    │    │   1│   4│   8│   5│    18
   Total  │   1│   1│   0│   6│   8│  13│  12│  21│  18│  30│  13│   123

                                TABLE IX.

                          HENNEPIN COUNTY, MINN.

         │                           Life-Ages
  School │No. │ 6  │ 7  │ 9  │ 10  │ 11 │ 12  │ 13  │  14  │  15  │  16
 Position│    │    │    │    │     │    │     │     │      │      │
  Grades │    │    │    │    │     │    │     │     │      │      │
    +    │   1│    │    │XI  │     │    │     │     │      │      │
    +S   │  17│VIII│VIII│    │     │XII │XI   │XIII │XIII  │      │
         │    │    │    │IX-3│     │    │     │XI   │XII   │XI    │XII
         │    │    │    │X   │     │    │XII-2│XII  │      │      │
    -S   │  21│    │    │    │X    │XI-3│     │     │XIII-2│XI    │XIII
         │    │    │    │    │IX   │    │XI   │X    │      │      │
         │    │    │    │    │     │X   │     │     │XII-2 │      │
         │    │    │    │    │XII  │    │     │     │      │XIII  │
         │    │    │    │    │XI   │VII │     │     │XI    │      │
    -1   │  28│    │    │    │XI   │XI-3│XI   │XI-3 │XII   │XI    │XIII-2
         │    │    │    │IX-1│VIII │    │     │     │      │      │
         │    │    │    │    │X    │X   │XII  │XII  │XI-2  │XIII-4│XI
         │    │    │    │    │IX   │    │     │     │      │XII   │
    -2   │  26│    │    │    │     │IX  │XII-2│XII  │(X)   │XIII-3│XIII-2
         │    │    │    │    │     │XI  │XI-2 │X-2  │XIII  │XII-2 │XII
         │    │    │    │    │     │    │X    │XI   │      │XI-5  │
    -3   │  19│    │    │    │     │    │XI   │(IX) │XII-2 │(X)   │XI-2
         │    │    │    │    │     │    │     │XI-3 │XI-2  │XI-XII│
         │    │    │    │    │     │    │     │X XII│      │      │
    -4   │   7│    │    │    │     │    │     │VIII │XI    │(X)   │XII
         │    │    │    │    │     │    │     │X    │      │XI    │
         │    │    │    │    │     │    │     │     │      │XII   │
    -5   │   4│    │    │    │     │    │     │     │(X)   │(X)   │(IX)
         │    │    │    │    │     │    │     │     │      │      │(X)
  Totals │ 123│1   │ 1  │ 6  │  8  │ 13 │ 12  │ 21  │  18  │  30  │  13

  An Arabic numeral after a Roman numeral indicates the number of
  cases, when more than one case occurs at any position in the table.
  Parentheses indicate cases testing presumable deficient or doubtful.
  S is a satisfactory school grade.

The summary of the Binet scale testing of this group according to the
valuation which we have adopted, shows two clear cases of tested
deficiency. One boy who was 13 years of age tested VIII and was the only
case sent to the State School for Feeble-Minded from this group. The
other was 16 years of age and tested IX. Besides the two presumable
deficients, seven other boys were uncertain according to our
interpretation, as judged by the Binet tests alone. One of them was 13
and tested IX, the others were 14, 15 and 16 and tested X. This would
make a total of 7% possibly socially deficient, since they were all
delinquent. This seems to be the largest estimation of deficiency which
would be justified on the basis of these test results. To show, however,
how important is the interpretation of the results obtained with Binet
examinations when treated in gross, it need only be stated that a few
years ago, when this study began, it was not uncommon to count all who
were retarded three or more years and testing XII or under as
feeble-minded. On that absurd basis, there would be 45 such cases (37%).
As we have considered at length the reasons for not counting a person as
even of doubtful intellect who tests XI or above or is less than three
or four years retarded, we do not need to rehearse them here.


Using our conservative basis for interpreting the results of Binet
examinations, let us now review the evidence of the proportion of
delinquents which is intellectually deficient. We shall compare the
available data on groups of tested delinquents which have not been
subjectively selected, provided that the data permit of restatement on
the basis of the borderlines we have adopted. The evidence of tested
deficiency on over 9000 objectively selected delinquents has thus been
assembled under approximately the same interpretation of the
borderlines. This should help to make it clear how extensive the
preparations must be for dealing with this problem of the defective
delinquent and where the needs are most pressing. It should also enable
us to discover when the estimates have been excessive. We shall confine
ourselves to the reports of objective test examinations, so that the
estimates do not depend upon the judgment of the examiner alone. A
bibliography of these studies is given at the close of the book. How
much more has been accomplished in this field in the United States than
abroad is illustrated by the fact that repeated search has failed to
discover any reports of Binet examinations on representative, randomly
selected groups of delinquents in any foreign country. Binet
examinations have been made of juvenile delinquents in Breslau (_34_)
and in Frankfurt a. M., and in London (_56_); but only upon selected

Those who wish to compare the results as to tested deficiency with the
subjective opinions of various estimators should consult the reviews of
this literature by Bronner (_6_) and by Gruhle (_121_). The effect of
such a comparison is an increasing conviction that it affords dubious
evidence of the relative amount of deficiency in different groups of
delinquents. Without objective tests, there is no means of telling what
amount of mental retardation the different experts would class as


Women in state penitentiaries are a small group among delinquents in
institutions. According to one study by Louise E. Ordahl and George
Ordahl[15] the frequency of tested deficiency is smaller among them than
among women committed to reformatories, who in general commit less
serious crimes. All except one of the 50 women prisoners enrolled were
tested with the Kuhlmann 1911 revision of the Binet scale. About half
were negro women. Only 6 (4 negroes) tested IX or below and were in our
group of presumably deficient by the tests. Twenty others (13 negroes)
tested one Binet age higher and were in the doubtful group.

If we consider the worst condition so far as intellectual deficiency is
concerned, we find it in the reformatories and training schools for
women. Dr. Weidensall applied the 1908 Binet scale to 200 consecutive
women, 16 years to 30 years of age, as they were admitted to the New
York Reformatory for Women at Bedford. Seventy-seven tested IX or under
and were within our presumably deficient group. An additional 74 tested
X and were in the uncertain group, although if we regard them all as
deficient because of their persistent delinquency, we have a total of
75% (_59_). These results were duplicated by Dr. Fernald (_16_). She
tested 100 other consecutive cases with the 1911 scale and found 41%
tested below X, our presumably deficient group. She regards these as
“feeble-minded with certainty.”

Dr. Katherine Bement Davis, the former superintendent at Bedford,
estimated herself that among 647 prostitutes who were inmates there, 107
were “feeble-minded (distinctly so);” 26 “border-line neurotic;” 26
“weak-willed, no moral sense;” 11 “wild, truant, run-a-ways.” This makes
a total of 26% of this group whom she apparently thought might possibly
be classed feeble-minded or of questionable mentality because of
deficient intellect or will (_11_). It is quite clear that the objective
tests give a much better basis for comparison of the Bedford group with
those which are to follow.

The professional prostitute confined in institutions for delinquents has
been carefully studied and tested by the Massachusetts Commission for
the Investigation of the White Slave Traffic, So Called (_36_). Three
groups of 100 each were examined “without selection, except that all had
a history of promiscuous sex intercourse for pecuniary gain.” One of the
groups consisted of young girls under sentence in the State Industrial
School for Girls, the House of Refuge and the Welcome House. A second
group consisted of those just arrested and awaiting trial in the Suffolk
House of Detention in Boston. The third was made up of women serving
sentence in the State Reformatory for Women, the Suffolk County Jail and
the Suffolk House of Correction. “These three groups represent the young
girls who have just begun prostitution, the women plying their trade on
the streets at the present time, and the women who are old offenders.”

The Binet tests were applied to 289 of the 300 women examined, and other
psychological tests were applied in doubtful cases. The ages ranged from
12 up. Only 10 were under 15 and 32 were 36 years of age or over. The
investigators classed no case as feeble-minded which did not test XI or
under, but they did not class as feeble-minded 107 other cases which
tested XI and under. The Commission's diagnosis is therefore
conservative. It regarded 154 cases (51%) as feeble-minded, 46 in the
detention house group and 54 in each of the others. If we ask how many
tested below our standard we can not tell exactly, since the report does
not state whether X.8 was classed as X or XI. It shows 81 tested IX or
under (27%) and these were nearly all, therefore, within the limits of
our group presumably deficient. Ninety-nine others tested X, a total of
60% testing below our borderline for presumable and doubtful deficients.
Since only 2 cases were under 14 years of age, these figures could not
be much disturbed by the younger girls. We can be reasonably sure, then,
that at least 27% of these prostitutes should be placed under permanent
custodial care, and probably 50% would be more nearly correct.

In a recent report of the Bureau of Analysis and Investigation of the
New York State Board of Charities[16] Dr. Jesse L. Herrick reports
testing 194 inmates of the state reformatory for women known as the
Western House of Refuge. The Stanford Scale was used, 25% tested IX or
under with that scale and 14% tested X. In the same bulletin the report
is made of Binet ages for 607 inmates of the New York Training School
for Girls. Four versions of the scale were used so that the estimates
are somewhat affected. Moreover, 97 girls were under 15 years of age.
The table of Binet ages indicates 20% testing IX or under and 28%
testing X.

Hill and Goddard (_30_) report examining a group of 56 girls who had
been in a reformatory and were under probation with a certain officer.
In this entire group they found only four who were not feeble-minded,
“as we usually define feeble-mindedness.” Presumably this means three or
more years retarded, including those who tested XII, so that it cannot
be regarded as a conservative estimate. No further data is provided for
interpreting the borderline.

Taking up the younger and milder girl delinquents, Dr. Haines reports
the examination of an unselected group of 329 at the State Girls
Industrial Home near Delaware, Ohio (_26_). They were all under 21 years
of age and represent less hardened delinquents than the older groups at
the reformatories for women. The Ohio group was tested with the Binet
1911 scale as well as with the Yerkes-Bridges Point Scale. Counting a
result of .8 of a year as placing the case under the next mental age
above, as we have in fixing the limits, we find that his results are
given with such excellent detail that we may fairly compare the
percentages with our standard for the Binet Scale. On this basis 70 of
these delinquent girls (21%) are clearly deficient and 55 more are in
the uncertain group, a total of 38%.

As a check upon results, we may compare the report of Miss Renz for 100
consecutive admissions to the same institution in 1912, tested with the
Binet scale (_47_). She found 29 tested IX or under, 49 tested X or
under, slightly more than was shown by the Haines tests. Miss Renz'
report, however, does not show how many of the girls were under 14 years
of age and might thus be excluded from the deficient groups.

In the California School for Girls, Grace M. Fernald[17] examined 124
cases as they entered the school. Twenty-four tested under XI with both
the Binet 1911 and Stanford revision. This is a further indication of
the less frequency of feeble-mindedness in the state schools for girls
than in the reformatories for women.

Dr. H. W. Crane reports the results of the Binet testing at Adrian, the
Michigan Industrial School for Girls, which receives only minors and
corresponds to the Ohio Industrial Home (_37_). The Binet 1911 scale was
used, but this grouping in mental ages may mean that a few more cases
are thus classed deficient than with our standardized borderlines which
place the subject in the higher age group when he scores .8. It is to be
remembered also that the borderlines for those whose life-ages are under
15 have not been as well standardized with the 1911 scale. The testing
was done under the direction of a state commission appointed to
investigate the extent of mental defectiveness (_37_). Dr. Crane was
assisted by three other workers. The results at Adrian show, among the
386 inmates, 131 or 34% tested in our groups of presumably or uncertain
intellectual deficients. Seventy-seven of these, in our uncertain group,
should only class as deficient because also delinquent. The
investigators give it as their opinion that 16.7% of the inmates were
feeble-minded but not reached by the tests.

The entire population of the Illinois State Training School for Girls at
Geneva was tested by Louise E. and George Ordahl.[18] The Kuhlmann
revision of the Binet Scale, supplemented by the Stanford Scale, for the
older ages, was used. Among the 432 tested 13 per cent. tested below our
borderline for the presumably deficient and 22 per cent. more in the
doubtful group.

Dr. Otis, resident psychologist at the New Jersey State Home for Girls
at Trenton, examined 172 girls between 10 and 20 years of age inclusive
(_43_). Since she said it was “a preliminary testing” and “not many of
the smaller girls were included,” we conclude that it was a somewhat
selected group. She regarded those who stand between eleven and twelve
as practically normal and those who stand below ten as without doubt
defective. She then publishes three groups: “Defectives,” 45% (77 cases)
high grade; “Morons,” 30% (52 cases); and “Presumably Normal,” 25% (43
cases). Since she does not give the distribution of the cases it is not
possible to tell how many of her group were less than four years
retarded. Her statement of the ages, however, shows that not more than 7
of the defectives could have been less than four years retarded and not
more than 12 of the combined group of defectives and morons tested X or
over. We may be sure, therefore, that at least 68% of these girls are of
questionable intellectual ability according to the conservative standard
adopted in this discussion.

Dr. Bridgman has reported the examination of 118 girls, 10 to 21 years
of age, successively admitted to the State Training School for Girls at
Geneva, Ill. She states that 89% (105 cases) “showed a retardation of
three years or more.” The distribution of cases is not given so that it
is not possible to tell how many testing X, XI, and XII were classed as
feeble-minded or how many tested only three years retarded. The
published estimate is undoubtedly extreme, but I have no means of making
a more conservative estimate on this group. It is interesting, however,
to note that only 14 of the cases were not sexually immoral. These were
all cases which were either dependent or sent because uncontrollable at
home and all tested as passable intellectually. She states that
“according to the Binet tests, 97% of the children (_5_) sent to this
institution because of sexual immorality are feeble-minded as well.”
This percentage also would be decidedly discounted on a conservative
test standard. In another place Dr. Bridgman makes the important
statement that of 400 girls admitted to Geneva 60% were suffering from
venereal disease (_4_).

Mr. Bluemel (_2_) found that 24 out of 50 girls sent from Judge
Lindsay's Juvenile Court in Denver to the State Industrial School or the
Florence Crittenden Home tested XI or under and four or more years
retarded. This is less conservative than our standard, which would
exclude those who tested XI as above even the uncertain group in

Dr. Pyle (_46_) has tested the 240 girls at the Missouri State
Industrial Home for Girls with his standardized group tests. These girls
are from 7 to 21 years of age and his table gives the results with each
of six tests. The most significant fact for our purpose is that with the
different tests from 50 to 88 per cent. fall below the averages of
normal individuals who are three years younger. He says, “Our figures
would indicate that about one-third of these delinquent girls are normal
and about two-thirds subnormal. Most of them are probably high grade
morons.” This is based apparently on 69% being the average of the
results of six different tests as to the percentages three years or more
retarded from their life-ages. He indicates, however, that 38%,
similarly calculated, are within the average deviation of the normal
groups for their life-ages. This indicates that the lowest 62% test only
as low as we should expect to find the lowest 21% of random groups of
corresponding ages. They should certainly not be regarded as testing


When we turn to those who are cared for locally in city or county
institutions, we find Sullivan (_56_) has examined 104 women and girls
held temporarily at the Holloway jail in London, most of whom were
between 16 and 25 years of age. Apparently the cases were especially
selected for examination and therefore do not represent the general
condition there. He was interested, however, in finding the relative
amount of deficiency among different classes of these inmates and he
gives the detailed results with the Binet 1908 scale on small groups of
these different types which we may classify by our standard as follows:

  Twenty non-criminal, either not guilty or guilty of unimportant
  offenses, who represent, he thinks, the ordinary conditions among
  the corresponding working class in this community, 3 presumably
  deficient, 5 uncertain; twenty criminal by reason of the occasion, 1
  presumably deficient, 6 uncertain; twelve impulsive criminals, 1
  presumably deficient, 2 uncertain; eight moral imbeciles, 2
  presumably deficient, 2 uncertain; twenty-four recidivists, 2
  presumably deficient, 8 uncertain; twenty prostitutes, 3 presumably
  deficient, 8 uncertain. Together these different types of women in
  jail form a motley group of 104 of whom 12 test presumably
  deficient, 31 uncertain, a total of 41%.

Ordinary prostitutes are about as frequently deficient as are those in
reformatory institutions, if we may judge by an important study of women
who were sex offenders but not in institutions for delinquents. The
report is by Dr. Clinton P. McCord, health director of the Board of
Education at Albany (_35_). One group consisted of fifty cases of sex
offenders who were not legally delinquents at the time but were living
in houses of ill-fame. Their ages ranged from 22 to 41 with an average
age of 27. Nine of these (18%) tested IX or under with the Binet 1911
and 18 tested X, a total of 54% presumably and doubtfully deficient.
Another 38 cases were staying at a House of Shelter where most of them
had been sent by the courts. Nineteen of these tested IX or under (50%),
while 13 more tested X, a total of 84%. Since their ages ranged from 12
to 40 years with an average of 18 we cannot tell how many might be above
the borderline on account of an age less than 15 years, but probably
very few. A third group consisted of 9 street walkers and 3 wayward
girls. Among these 7 tested presumably or doubtfully deficient.

The McCord study of prostitutes not legally delinquent at the time of
examination is confirmed by the Virginia State Board of Charities and
Corrections in a special report to the General Assembly which gives the
results of examining the prostitutes in an entire segregated district in
one of the Virginia cities (_58_). Its table shows that, among 120 of
these women, 43, or 36%, tested approximately under our borderline for
the presumably deficient, while 67 cases, or 56%, tested below
approximately our borderline for the presumably passable intellects.

These results are similar to Weidensall's[19] findings among the
unselected group of unmarried mothers in the Cincinnati General
Hospital. While she does not give the number tested with the
Yerkes-Bridges scale, she indicates that 48% tested as low-grade morons
or worse, which should correspond to a test age of IX or lower.
Twenty-two per cent. had intelligence coefficients of .50 or less and
32%, from .51 to .70. A _Study of Fifty Feeble-Minded Prostitutes_[20]
by Mary E. Paddon gives an admirable summary of the social history of
prostitutes who tested deficient.

Dr. Bronner has made a careful study with Binet tests of a younger group
of randomly selected girls at the Cook County Detention Home which is
connected with the juvenile court at Chicago. The group included 133
girls 10-17 years of age inclusive, who were held awaiting a hearing or
were temporarily cared for in the detention home. The Binet tests were
given to all who did not show clearly that they were of passable
mentality by completing the sixth grade or above without retardation,
and passing school tests in long division and writing from dictation. A
14-year-old child “passing all the 10-year-old tests and some, but not
all, of the 12-year-old tests,” was regarded as doubtful. She was not
classed as feeble-minded without further testing and study. Dr. Bronner
does not state her criterion for the borderline with the younger
children, but we may judge that her borderline was more likely than ours
to have classed a child in the presumably deficient group. Her summary
shows only 15 girls “probably feeble-minded” (11.2%), and 2 others
“possibly” so. From her description we may suppose that the “probable”
group were comparable with our test standard of presumably deficient,
plus perhaps a few conative cases.

Mention should also be made of the work of Dr. Bronner to which we
referred under the earnings of the mentally retarded (_6_). This group
of 30 randomly selected delinquent women at a local detention home in
New York tested, with two or three possible exceptions, no lower than a
similar group of women servants who had never been offenders. Her data
do not enable us to determine how many would fall below our borderlines.

Stenquist, Thorndike, and Trabue (_54_) report the results with the
Binet 1911 tests, under a slightly modified procedure, for 75 randomly
selected dependent and 4 delinquent girls cared for by a certain county,
excluding those children within the county sent to an institution for
the feeble-minded. The children were from 9 to 16 years of age, with a
medium age of 11 years. The line between the delinquent and dependent
groups with these younger children becomes rather obscure. They state:
“A child may, in the county in question, become a public charge by
commitment by an officer of the poor-law on grounds of destitution, or
by an officer of the courts on grounds of delinquency.... The decisive
factor is often simply whether the parents are more successful in
getting justices to commit their children than in getting poor-law
officers to do so.” With the detailed records which they give it is
possible to apply our standard even for the immature, although it is
certainly less adequate for those under 15 years of age tested by the
1911 scale. I have translated their corrected Binet ages back to the
original test ages, since their summary of retardation in terms of years
below average ability at each age is not comparable with our borderline.
Among the 79 girls who are mostly dependent, there are 5 girls, or, 6%,
who fall within our presumably deficient group and 8 in the doubtful
group, a total of 16%. So far as serious deficiency is concerned the
situation is undoubtedly worse among delinquents than among
corresponding groups of dependents. The figures of these investigators
show this for their group of boys, to which we shall refer later.

Certain other groups of women and girls have been examined with the
Binet or other tests, but the results are of little significance for
judging the problem of deficiency objectively, since the individuals
were either selected for examination because they were thought to be
abnormal mentally or because there are not adequate norms for
determining the borderlines with the particular tests used. At the New
York State Training School for Girls in Hudson, we find that 208
selected cases who were not profiting by their training were examined
with the 1911 scale. They ranged in life-age from 12 to 20. We cannot
determine how many were under 14 years of age, or how much effect might
have been produced by selecting dull cases; but 44 tested IX or under
and 52 tested X (_158_). Dr. Spaulding (_183_) used Binet and other
psychological tests on a group of 400 inmates of the Massachusetts
Reformatory for Women at South Framingham; but she gives only her
judgment based on the examination and history of the cases so that we
have no data on this group for comparison. Her statement that 16.8%
showed “marked mental defect, _i. e._, the moron group” and 26.8% showed
“mental subnormality (slight mental defect)” is an excellent
illustration of the best type of subjective judgment on consecutive
cases, since she is familiar with test results. For her purpose of
deciding how to care for the women it is of undoubted value, but for
comparative purposes it is clear that it is impossible to tell how her
subjective opinion would agree with that of an equally competent
diagnostician, or what is meant by her terms “feeble-minded” or
“subnormal.” For scientific purposes the Binet results for her group
would be of much value, for we should like to know whether the
conditions at Bedford are typical among the women's reformatories for
the older offenders.

Dr. Rowland used psychological tests other than the Binet scale with a
group of 35 at the Bedford Reformatory for Women, but there are no
adequate norms for the comparison of her results with the general
conditions (_49_). Baldwin (_1_) has shown that delinquent colored
girls, 13 to 21 years of age, in the girls' division of the Pennsylvania
Reformatory school at Sleighton Farm are inferior to white girls in the
same institution in a learning test. As cited by Gruhle (_121_), Cramer
(_10_) used an Ebbinghaus completion test, definition tests, etc. with
376 delinquent girls in Hanover, but there are no borderlines for
comparison. As cited by Bronner, von Grabe gave several psychological
tests to 62 prostitutes treated in the city hospital in Hamburg and
compared them with a control group of 30 (_6_).

The most striking conclusion that comes out of the study of this
evidence of frequent deficiency among delinquent girls and women is the
close association between sex offenses and deficiency. One hundred and
four out of 118 consecutive admissions at the Illinois training school
were known to be sexually immoral. At Bedford 94 out of 100 consecutive
cases had records of immorality, while three-fourths of the same group
tested questionable in intellect by our standards (_11_). This evidence,
taken with the report of the Massachusetts' Commission and the tests of
sex offenders who were not at the time legally delinquents, reported by
McCord, and the Virginia Commission, leaves little doubt that there is
an excess of deficiency among this type of offender. Many of these
deficient girls probably at first drift into the life of prostitution.
They are passive rather than active agents. This distinction in the
nature of the offense accounts for some of the difference between the
sexes in this form of delinquency. Furthermore our public attitude in
matters of social hygiene has made the isolation of the female sex more
common. Part of this may be due to the greater difficulty of proof in
the case of men and boys, but in part it undoubtedly means that men have
not been held to as high a moral standard as women in this regard. The
greater frequency of deficient sex offenders among girls, does not mean
that girls are more likely than boys to be active sex offenders. They
are, however, more likely to be isolated for such offenses, and also
more likely to be passive offenders.

The greater amount of deficiency found among female delinquents than
among corresponding groups of males is thus easily accounted for by
frequent association between deficiency and sex delinquency on the part
of girls and women. The combination of legal sex delinquency and
deficiency is due both to a native sex difference and a difference in
social attitude toward the two sexes as to this form of offense.
Whichever may be the main cause of the facts found, it is clear that
deficiency is, today, most serious among female offenders. It is so
serious that some of our reformatories for women might even prove to be
practically institutions for deficient delinquents. It is in this type
of institution without doubt, that the immediate problem of the
deficient delinquent is most pressing. Permanent guardianship, if not
isolation, for at least a third of the inmates of an institution like
Bedford which shows this amount of clear tested deficiency, under our
very conservative standard, would seem to be a wise move in social
hygiene. It should be undertaken at once with vigor. A more fundamental
change in our social attack of this problem means state guardianship
before adolescence for all girls testing presumably deficient under our
standard, when their deficiency is not due to removable handicaps.


For the purpose of judging the importance of the question of
feeble-mindedness among the most serious criminals, those committed to
the state prison, we have a very important study by Rossy (_48_). Three
hundred cases were taken at random with the exception of a few selected
cases on which a report was requested. In this group, thirty prisoners
could not be examined either because of language difficulties or because
of their refusal to be tested. The Point Scale of Yerkes and Bridges was
used and the results are presented in terms of mental ages on that
scale. The examiner considered all those testing XI or under as
feeble-minded and found 22% of the 300 in this class. This is less
conservative than even our doubtful standard, but I estimate that 16%
would fall within our doubtful and presumably deficient groups. This
includes 11% who test X or under with the Point Scale plus 54% of those
who tested XI. This estimate is made on the basis of the tables given by
Haines (_26_), comparing Binet 1911 results with those of the Point
Scale on the same individuals. It adds the proportion of those testing
XI with Point Scale, who would test nearer X with the Binet 1911 scale.

Ordahl[21] examined 51 convicts in the penitentiary at Joliet, Ill. They
“were selected in a manner thought to secure fair representation of the
prison population as a whole.” The Kuhlmann 1911 Binet scale was used
and supplemented by tests for 13 to 18 years taken from the Stanford
scale. It is possible that selection affected the results with this
small group, since 25% showed test ages of IX or under and 36% tested X
or under.

Haines tested with the Point Scale 87 consecutive admissions to the Ohio
penitentiary (_24_). He found 18% tested below a record corresponding to
X.6 on the Goddard 1911 scale, which is about the upper limit of our
doubtful group.

That a smaller proportion of the state prison inmates is found
intellectually deficient than is found among the inmates of the
industrial schools is not surprising. This may be due to various causes.
Among these may be mentioned the failure to recognize feeble-mindedness,
heretofore, among the younger delinquents while the adult feeble-minded
were more carefully isolated in their proper institutions. The deficient
adults have also been reduced in frequency by the excessive mortality.
Probably the feeble-minded are not so likely to plan or commit felony as
lesser crimes and misdemeanors. Moreover the adult feeble-minded may be
more stable and less inclined to delinquency than adolescents. Whatever
may be the explanation, deficiency generally does not seem to be as
common among the inmates of a state prison as among minor delinquents in
states which are in the forefront in the care of their feeble-minded.

The state reformatories reach a class of delinquents between those of
the state prisons and the state industrial schools. In Minnesota all the
inmates of the reformatory except 80, who were disqualified by inability
to speak English or otherwise, were tested by Dr. E. F. Green. Men are
sent there only between the ages of 16 and 30, so that his table of
mental and life-ages gives us the opportunity to apply our criteria
accurately. Thirteen per cent. of the 370 examined tested IX or under
and were presumably deficient, while 22% more were in the uncertain
group testing X (_22_).

In a report of the Binet results with 996 inmates of the Iowa
Reformatory, which Warden C. C. McClaughry kindly sent me, 200 tested IX
or under and 146 tested X, a total of 35% including the doubtful group.
The range of ages was from 16 to 49. The Warden notes that the tests
were not made by an experienced psychologist. “In many cases it is
suspected that the crafty criminal was endeavoring to lower his standing
as to mentality in the hope of excusing or mitigating his crime in the
eyes of the Board of Parole.” The results, however, agree well with what
has been found in similar institutions.

Supt. Frank Moore of the New Jersey Reformatory at Rahway says, “Nearly
every young man who has entered our institution in the last eighteen
months has been tested by this system (Binet), and the results have
shown that at least 46 per cent. were mentally subnormal” (_38_). By his
discussion this seems to mean that they tested below XII which would
mean that all those testing XI were less deficient than our standard for
doubtful cases. These young men were from 16-25 years of age and 17.5%
of them had had one year or less in school. Ten per cent. could not be
examined because of unfamiliarity with English. A later report in 1912
regarding the same institution (_42_) says that 600 of the inmates have
been examined with the Binet tests in two years, but does not state how
these were selected. Of those examined we are told “48% are of the moron
type of mental defectives, ranging in mentality from three to eight
years, below the average normal adult.” Again, no further information is
given so that it is impossible to allow for those testing X or XI or for
the cases only three years retarded. Both of these estimates at the New
Jersey Reformatory are excessive when judged by conservative

Dr. Fernald has applied 11 objective tests to a representative group of
100 inmates at the Massachusetts Reformatory (_15_) but the norms for
the tests which he used were obtained, for the most part, by testing a
dozen boys so that the line which he draws for the limit of the
defectives is largely a matter of his expert opinion and the estimation
loses objective character. He estimates that 26% of his group whose ages
run from 15 to 35 inclusive were defective. Beanblossom[22] has
published an account of tests on 2000 inmates of the Indiana
Reformatory. Some of the Binet tests as well as other tests were used
but the published results do not admit of reinterpretation.

Comparing the reports from the Minnesota, Iowa, and New Jersey
reformatories with the tested deficiency found in institutions for women
delinquents on the basis of the same borderline with the scale, the
records indicate clearly that the percentage of feeble-mindedness is
greater in the reformatories for women. At the Bedford Reformatory for
women, for example, Dr. Weidensall's results show that the corresponding
borderline to that used in the New Jersey men's reformatory which
reported 46% deficient, would class 100% at Bedford as feeble-minded,
where only one case in 200 tested as high as XII. A conservative
estimate of tested deficiency in men's reformatories from the above data
would be from 15 to 20%.

In the state institutions for minor delinquents, usually called
industrial schools, we have several studies of representative groups
with sufficient data to make objective interpretations comparable with
our standard. In Ohio, Dr. Haines (_26_) reports on the examination of
671 delinquent boys 10 to 19 years of age at the Boys' Industrial School
near Lancaster. Interpreted as we have indicated for the Ohio
Institution for girls, we find 100, or 15%, in the group testing
presumably deficient and 179 in the doubtful group, a total of 42% clear
and questionable.

In the corresponding Michigan Industrial School at Lansing, Dr. Crane
(_37_) shows by his table of mental and life-ages that 52 out of the 801
unselected inmates, or 6% are presumably deficient and 171 below the
presumably passable, or 21%. This is only a slightly greater number than
our criterion would provide, if .8 of a year were not classed in the
next higher mental age by these examiners. The age of those examined ran
from 10 to 17.

T. L. Kelley in his “Mental Aspects of Delinquency”[23] gives the
results for an extensive series of measurements and tests on about three
hundred boys in the Texas State Juvenile Training School. On the basis
of an analysis of his tests he estimates that 20% of the boys there
should be in a school for the feeble-minded. Interpreting his original
data for the 1911 Binet tests on the same basis as our own, 8% fall
within the clearly deficient group and 9% in the doubtful. The latter on
account of their delinquencies might also be included as feeble-minded.

The 215 inmates of the Whittier State School in California were examined
by J. Harold Williams with the Stanford revision of the Binet scale
(_61_). The boys were 10 to 22 years of age, median 16 years. He states
that 32% were feeble-minded in the sense of having Intelligence
Quotients less than .75. This is a standard which would include about 2%
of those tested with the scale, so that we may consider the bulk of them
as within our presumably deficient and uncertain groups combined. He
also states that approximately 14% tested below X with the Stanford
Revised Scale. In another paper he shows that the amount of
feeble-mindedness was much different among the different races
represented in the institution. With 150 cases according to his standard
there were 6% feeble-minded among the whites, 48% among the colored, and
60% among the Mexican and Indian races. In this group 64% were native
whites, 21% of Indian or Mexican descent and 15% colored. “While the
negro population of California constitute but 0.9% of the total, yet the
results of this study indicate that more than 15% of the juvenile
delinquents committed to the state institution are of that race.” It is,
of course, of fundamental importance in regard to all estimates of
feeble-mindedness among delinquents to consider the racial conditions at
the particular institution.

A New Hampshire Commission tested the children in its State Industrial
School. Its table shows that among the 113 boys tested at least 37% were
presumably or doubtfully deficient. To these should be added some 14
years of age and over who tested X, in order to have the total number
below our borderline for the presumably passable cases. The published
table does not separate these from the 13-year-olds (_40_). Hauck and
Sisson report in School and Society for September, 1911, tests made at
the Idaho Industrial School, which receives both boys and girls from 9
to 21 years of age, including some children who would be classed as
dependents but can not be cared for elsewhere in the state. Supposing
that our standard applied to the 1911 scale which was used, among 201
tested there were 5 presumably deficient and 13 doubtful.

A partially selected group of 341 inmates at the St. Charles, Ill.,
State School for Boys chosen in such a way that it naturally would
somewhat increase the frequency of deficiency, was tested by Dr. Ordahl
with Kuhlman's form of the 1911 scale supplemented by the Stanford Scale
above XII. The results showed 11% in the presumably deficient group and
20% in the doubtful group (_41_).

One of the main uses of the objective scale is to demonstrate that the
same conditions do not prevail in various institutions which, except for
this objective evidence, might be expected to care for the same type of
inmates. This is illustrated by the comparison of the above studies in
Ohio and Michigan with that made at a similar state school for
delinquent boys in Indiana reported by Hickman (_12_, _28_). The Binet
1911 tests, Goddard's adaptation, were applied to 229 new boys 8 to 17
years of age inclusive, admitted to the Indiana Boys School at
Plainfield. Among these, 68 boys (30%) tested below our borderline for
the clearly deficient and 53 more within the doubtful region, a total of
48%. There seems little doubt that this represents a significant
difference from the condition at the corresponding Ohio and Michigan
schools where only 15% and 6% respectively tested clearly deficient on a
corresponding standard. An interesting commentary on the necessity of
reinterpreting the borderline for feeble-mindedness on the scale arises
when we note that Hickman says: “One hundred and sixty-six, or about 75%
of the whole number tested, tested as much as three years or more below
normal, and therefore would be classed as feeble-minded to a greater or
less degree.”


It seems likely that in city and county institutions deficiency is most
common among repeaters in the jails or workhouses. One study has been
made of a randomly selected group of repeaters who were in the jail of a
Virginia city for fixed sentences of not more than a year. The
examinations are summarized in the Special Report of the Virginia State
Board of Charities and Corrections (_58_). In this Virginia city 50
whites of both sexes and 50 negroes of both sexes were examined. Among
the whites, 18 tested IX or under and 5 more tested X. Among the
negroes, 24 tested IX or under and 10 tested X. The percentages would be
just twice these numbers, a total of 61% below passable capacity in this
group of 100. If such is the condition in other jails in other parts of
the country, it indicates one of the most serious hot beds of deficiency
among delinquents. The repeaters in this city jail during three years
were responsible for 60% of the commitments to jail, although only about
one-fourth of the 33,306 arrests in this city during the three years
resulted in commitment to jail. The feeble-mindedness among the
repeaters, therefore, may be little indication of the frequency of
deficiency among those arrested in the city. The repeaters represented
only a third of those committed to jail during this period and this
third was probably the most deficient among those committed, since
recidivism goes with deficiency. Moreover, those committed to jail are
probably more likely to be deficient than those who escape jail
sentences. To assume, therefore, that 61% of this city's delinquents
were of doubtful ability would be clearly unjustified, and yet this sort
of reasoning about the frequency of deficient delinquents has been all
too common.

Gilliland[24] tested one hundred male inmates of the Columbus, Ohio,
Workhouse (28 negroes) selected so as to attempt to represent the
different offenses about in their proportions. He gives the results in
point scores with the Yerkes-Bridges scale, which may be translated only
roughly into Binet 1911 ages by Haines' data, as I have indicated for
the study by Rossy. All were 18 years of age or over, so that I estimate
14% would fall into our presumably deficient group including only the
proportion of those under 64 points who would test as Binet IX or less.
The doubtful group would include 17% more, including the proportion
under 66 points who would test X or under.

Among the local institutions supported by the county or city, the most
serious delinquency is probably found in the group reported by Kohs at
the Chicago House of Correction (_33_). He tested with the 1911 Binet
scale 335 consecutive cases between 17 and 21 years of age. Among these
were 72 cases (21%) who tested clearly deficient according to our
standard, and 95 cases doubtful, a total of 50% at least uncertain in
intellectual ability.

Through the courtesy of Catherine Mathews, who made the examinations for
the psychological clinic of the University of Pittsburgh, which is under
the direction of Dr. G. C. Bassett, I am able to give the records of 125
consecutive admissions to the Allegheny County Detention Home. The
institution is known as the Thorn Hill School. It is situated some miles
outside of Pittsburgh and provides on the cottage plan for about 300
boys. The boys are sent from the Juvenile Court for milder training than
that at the state school. The school has also been found to furnish a
necessary place to care for cases of feeble-minded delinquent boys who
cannot be immediately admitted to the state institution on account of
its crowded condition. A detention home is also provided in the city for
juvenile court children awaiting trial or the disposition of their
cases. These are not included in the Thorn Hill group.

Among the 125 consecutive cases at Thorn Hill, omitting two cases which
are probably dementia praecox, there were 37, or 29%, who tested
presumably deficient according to our standard, and a total of 68 cases,
or 55%, presumably and doubtfully deficient. It is to be remembered that
our standard for the immature was arranged for the 1908 scale and not
the 1911 scale which was used here, although the difference would be

                                 TABLE X.


 Life-Ages │                        Mental Ages
           │ IV  │  V  │ VI  │ VII │VIII │ IX  │  X  │ XI  │ XII │Totals
         18│     │     │     │     │     │     │    2│     │     │     2
         17│     │     │     │     │    1│    3│    3│    1│    2│    10
         16│     │     │     │     │    2│    5│    7│    7│    1│    22
         15│     │     │     │    1│    3│    8│    8│    8│    1│    29
         14│    1│    1│     │     │    3│    4│    6│    5│    2│    22
         13│     │    1│     │     │    3│    4│    3│    4│    3│    18
         12│     │     │     │     │     │    4│    4│    1│    1│    10
         11│     │     │     │    1│     │    1│    1│     │     │     3
         10│     │     │     │    1│    1│     │    2│     │     │     4
          9│     │     │     │     │    2│    1│     │     │     │     3
          8│     │     │     │    1│     │     │     │     │     │     1
   Totals  │    1│    2│    0│    4│   15│   30│   36│   26│   10│   124

The accompanying Table X shows the distribution, omitting the dementia
praecox cases. It classes .8 as in the next higher test age and shows
the last birthday for life-age. In interpreting these figures it is
highly important to remember that Thorn Hill is necessarily used at
present to shelter deficient boys who are dependent or delinquent and
cannot be otherwise provided for. This is undoubtedly a wise temporary
relief until the state takes proper care of these unfortunates. Under
the cottage system which prevails at Thorn Hill the segregation can be
made with little interference with the main purpose of an institution
for delinquents. It is apparent that any deductions made from the large
frequency of feeble-mindedness among these delinquents without
considering the particular local conditions under which they are found,
would be wholly unjustified. A similar local condition probably explains
the high percentage of tested deficiency among the following group of
boys in the Newark, N. J., detention home.

A representative group of 100 in the detention home at Newark, “chosen
entirely at random,” was examined by Mrs. Gifford, and reported by
herself and Dr. Goddard (_17_). In this group of 100 there were 66
between the ages of 14 and 17 who were at least four years retarded
mentally. Moreover, among these 66 “none tested over eleven and only a
few at that age.” Only average mental ages are published, so that we
cannot tell how many tested XI or X, but the statement quoted shows that
few of these 66 would test XI, and would thus be above our doubtful
class. We may, perhaps, suppose that about 66% of this group in the
Newark detention home tested as low as the randomly selected group at
Thorn Hill, Pittsburgh.

That the explanation of the excessive amount of deficiency found at
Newark lies in the inadequate provision for recognized feeble-mindedness
in that community is indicated by the Fourteenth Annual Report of the
Newark City Home. It states that “the lack of a state institution for
defective children made it necessary to commit to the City Home many
children, who, on account of physical defects and psychic disturbances,
have become juvenile delinquents.” A statistical table shows that of 181
boys, 151 were either illiterate or below the fifth grade in school in
spite of the fact that the average age of the boys at the school is 13
years. This shows clearly that the differences between the test results
at this institution and those in Minneapolis, Chicago, and elsewhere, is
not the result of different methods of giving the tests. It seems to be
mainly due to inadequate state provision for recognized feeble-minded

Among the more serious juvenile court offenders we have a group of 1000
recidivists referred to Dr. William Healy at the Psychopathic Institute
connected with the Chicago Juvenile Court. The cases are not tabulated
separately for the sexes as to mentality. They were all under 21 and
averaged between 15 and 16 years of age. While he used the Binet tests
quite generally, as well as his own and Miss Fernald's series (_125_),
Dr. Healy has not summarized his data in reference to the test
standards. Nevertheless, according to his experience after the results
of the test examinations were known, he classified only 89 of these
cases as moron and 8 imbecile, a total of only 9.7% feeble-minded.
Another group above these amounting to 7.9% was classed as of “subnormal
mentality—considerable more educability than the feeble-minded” (_27_,
p. 139).

From the same psychopathic laboratory comes the estimates of Dr. Bronner
(_7_) of a group of less serious offenders, some of whom were in court
for the first time, a group at the Cook County Detention Home connected
with the Juvenile Court in Chicago, where cases are held for trial or
until other disposition can be made of them. I have already reported her
results with the Binet tests for the girls in this group. Using the same
standard which was there described, she found among 337 boys 7 to 16
years of age 7% “probably feeble-minded,” and 2.4% doubtful, a total of
9.4% “possibly feeble-minded.” As nearly as I can tell from the
description of the borderline which she used with the tests, a boy was
perhaps slightly more likely to be regarded as testing probably
deficient than by our standard for the presumably deficient. Inasmuch as
Miss Bronner worked with Dr. Healy, this may throw some light on the
test standard which he had in mind in connection with his more serious

By means of Bluemel's study of different classes of juvenile delinquents
who passed through Judge Lindsay's Juvenile Court in Denver, we are able
to compare the intellectual ability of a group which was on probation,
about half of whom were first offenders, with groups sent to the Boys'
and Girls' State Industrial Schools (_2_). Although the report does not
so state, I should judge that the cases were objectively selected. The
published data is not adequate to state the results on the basis of our
conservative borderlines; but we can note the cases which tested XI or
below and were four or more years retarded with the 1911 Binet Scale
(Goddard's modification). This only differs from my broadest
interpretation by also including those that test XI. On this basis 6 of
the 100 probationers were possibly deficient; 9 of the 50 boys sent to
the State Industrial School, and 24 of the 50 girls sent to the State
Industrial School or Florence Crittenden Home. These are all somewhat
excessive estimates of the amounts of deficiency in this group as judged
by the interpretation we have been using. A more telling comparison of
the mentality of these groups may be made by weighting each retarded
case by the tests according to the number of years he is retarded. The
amount of retardation alone averages 1.3 years for the group of
probationers, 1.8 for the boys at the state school, and 3.8 years of the
institutional group of girl delinquents. Fifty first offenders among the
probation group average 1.1 years retarded. The girls and the more
serious juvenile delinquents in these younger groups show more

The Stenquist, Thorndike, and Trabue study of children 9 to 16 years of
age, who were county charges as delinquents or dependents in a single
county, provides results for a group of 104 delinquent boys. Translating
their records as I have explained for the girls in the group, we find 11
of these presumably deficient and 18 doubtful, a total of 28%. So far as
their delinquency is concerned these probably correspond to the local
institution groups. While there is little difference in the average
mentality of the groups of delinquent and dependent children in this
county shown by tests there is apparently some difference in the
frequency of serious deficiency. In their corresponding group of 63
dependent boys who were county charges, 2 are in the presumably
deficient group and 10 in the doubtful, a total of 19%. Miss Merrill
found only 0.8% in our presumably deficient group and 1.6% uncertain in
a group of 250 dependent children at the Minnesota State home (_149_).

Dr. Pintner reports the examination of 100 cases in the Columbus, Ohio,
Juvenile Court who were in the detention home waiting to be disposed of
or held for trial.[25] He does not say whether they were selected cases
among those in the home, but we may presume that they were more serious
offenders than the usual juvenile court cases not in the home. Their
ages ranged from 7 to 20 years. He used the Binet 1911 series and
allowed double credit for any test passed in the XV or adult series. By
placing his borderline so that a person testing 3.1 years retarded if he
scored under XII would be regarded as feeble-minded, Dr. Pintner found
46% feeble-minded in this group. Under the same standard about 20% of
the Minneapolis group would be classed as feeble-minded, instead of 2 to
7% under our more conservative borderlines.

In a preliminary report of the doctorate examination of Dr. Olga L.
Bridgman (_132_) I find that she reports testing 205 delinquents and 133
dependent children sent to the psychological clinic of the University of
California. She found 36% of the delinquent and 26% of the dependent
cases thus especially selected for clinical examination to be
“definitely feeble-minded,” but the preliminary report does not enable
one to judge the standard used for her borderline (_3_).

Ordahl's study[26] of 61 cases who were wards of the San Jose Juvenile
Court is not comparable with other groups since both sexes, both
dependents and delinquents and ages from 3 to 44 were included.

Dr. Hickson (_8_) reports concerning some 2700 cases selected especially
for examination from those passing through the municipal court in
Chicago, in the divisions of the Boys Court, the Morals Court and the
Domestic Relations Court. His tables state only average mental ages, and
he classes 728 boys who average XI.11 as morons, so that I am unable to
make any comparisons with his data.

Dr. Walter S. Cornell (_92_) published in 1912 the results of Binet
tests on 100 cases at the Philadelphia House of Detention among whom 64%
tested three or more years below normal and 41% four years or more below
normal. We are unable to tell how many of these tested X or above and
were thus of questionable deficiency. He also gives the results merely
with the years of retardation for a group of 73 “mildly delinquent boys
of Miss Wood's special school and the Children's Bureau (mostly
truants).” Of this group 46% were three years or more and 25% four or
more years retarded according to the tests. Again we are unable to judge
how the cases were selected or what was the mental age distribution so
as to discover those that fall under our borderlines, especially under
the borderline of XI for the mature.

Psychological examinations have been employed in connection with the
children at the Seattle Juvenile Court. Although the results are not
presented in a form which can be compared with other localities, Dr.
Merrill, the physician who directs the general clinic, is of the opinion
that feeble-mindedness was the cause of the delinquency of only 6% of
421 consecutive cases (_148_). Previously in the same court, Dr. Smith,
the psychologist, on the basis of tests, reported among 200 consecutive
cases only 11 cases as feeble-minded, 5 as mentally defective, and 8 as
“moral imbeciles,” a total of 13.5% (_53_).

Frau Dosai-Révész (_13_) gave a number of tests to 40 boys, 9 to 16
years of age, selected from the boys training school of the Children's
Protective League in Hungary. The cases which she classified as morally
feeble-minded were found to test between the normal and the
feeble-minded groups.

As yet only the preliminary announcement has appeared of a study of a
thousand delinquent boys and girls with the Point Scale which has been
made by Bird T. Baldwin. It is to be published as a Swarthmore College
Monograph (Psychol. Bull., 1917, _14_, p. 78).

The reader should also consult the series of articles by L. W. Crafts
and E. A. Doll appearing in the Journal of Delinquency beginning with
May, 1917, on “The Proportion of Mental Defectives among Juvenile
Delinquents.” It is especially valuable as a critique of the conditions
desirable for exact comparison of the results of different

A Bibliography of Feeble-Mindedness in Relation to Juvenile Delinquency,
compiled by L. W. Crafts, may be found in the Journal of Delinquency,
Vol. I, No. 4. In Chap. II of his _Problems of Subnormality_, Dr. Wallin
gives an admirable review of numerous studies of tested groups.


In bringing together these studies in which we can make somewhat
comparable estimates of tested deficiency covering over 9000
delinquents, it seems possible to analyze further the question of the
deficient delinquent. Comparison of the amounts of deficiency on an
objective basis is scientifically a big step in advance from a reliance
upon the subjective opinion of experts who cannot possibly have the same
standard of deficiency in their minds. The results of the comparable
investigations, on the basis of the above reinterpretation of the
borderlines, are brought together in Table XI. The frequency of tested
deficiency which is found among about the lowest 0.5 and 1.5%
respectively of the population generally is there shown for these
different groups of delinquents. This review of the studies thus
assembled enables us to correct a number of impressions that have become
prevalent by the early studies, as well as to formulate the general data
in regard to the deficient delinquent in a manner that places the
practical control of this problem on a safer foundation. We shall
summarize the data under four heads.


  _Comparison of the frequency of tested deficiency among objectively
    selected groups of delinquents reinterpreted on roughly the same
      borderlines, which are often not those used by the original
 investigators. “Presumably deficient” in the table corresponds roughly
 to about the lowest 0.5 per cent., and the doubtful group to about the
             next 1.0 per cent. in the general population_

                            │          │          Percentages
   Group and Investigator   │  No. of  │Presumably│ Doubtful │   Both
                            │  Cases   │deficient │          │
       Women and Girls      │          │          │          │
                            │          │          │          │
 STATE INSTITUTIONS         │          │          │          │
                            │          │          │          │
     _Penitentiaries_       │          │          │          │
 Illinois Penitentiary (L.  │        26│        15│        27│        42
   E. and G. Ordahl) Negro  │          │          │          │
 Illinois Penitentiary (L.  │        23│         9│        30│        39
   E. and G. Ordahl) White  │          │          │          │
                            │          │          │          │
     _Reformatories_        │          │          │          │
 Bedford Reformatory, N. Y. │       200│        38│        37│        75
   (Weidensall)             │          │          │          │
 Bedford Reformatory, N. Y. │       100│        41│        24│        65
   (M. R. Fernald)          │          │          │          │
 Western House of Refuge, N.│       194│      (25)│      (14)│      (39)
   Y. (Herrick)             │          │          │          │
                            │          │          │          │
     _Training Schools_     │          │          │          │
 State Home for Girls, N. J.│       172│          │          │      (68)
   (Otis) Partially selected│          │          │          │
 Girls Industrial Home, Ohio│       100│      (29)│      (20)│      (49)
   (Renz)                   │          │          │          │
 State Industrial School and│        50│          │          │      (48)
   Florence Crittenden Home,│          │          │          │
   Colo. (Bluemel)          │          │          │          │
 N. Y. Training School for  │       607│      (20)│      (28)│      (48)
   Girls (Hall)             │          │          │          │
 Girls Industrial Home, Ohio│       329│        21│        17│        38
   (Haines)                 │          │          │          │
 Illinois State Training    │       432│        13│        22│        35
   School for girls (L. E.  │          │          │          │
   and G. Ordahl)           │          │          │          │
 Industrial School for      │       386│        14│        20│        34
   Girls, Mich. (Crane)     │          │          │          │
 California School for Girls│       124│          │          │        19
   (G. M. Fernald)          │          │          │          │
                            │          │          │          │
 COUNTY AND CITY            │          │          │          │
                            │          │          │          │
     _Sex Offenders_        │          │          │          │
 Sex Offenders not under    │        88│        32│        35│        67
   arrest, Albany, N. Y.    │          │          │          │
   (McCord)                 │          │          │          │
 Unmarried mothers,         │          │      (48)│          │
   Cincinnati General       │          │          │          │
   Hospital (Weidensall)    │          │          │          │
 Professional prostitutes,  │       300│        27│        33│        60
   Mass. (State Commission) │          │          │          │
 Prostitutes in a segregated│       120│        36│        20│        56
   district in a Virginia   │          │          │          │
   City (State Commission)  │          │          │          │
                            │          │          │          │
     _Juveniles_            │          │          │          │
 Cook County Juvenile       │       133│        11│          │
   Detention Home, Chicago  │          │          │          │
   (Bronner)                │          │          │          │
                            │          │          │          │
        Men and Boys        │          │          │          │
                            │          │          │          │
 STATE INSTITUTIONS         │          │          │          │
                            │          │          │          │
     _Penitentiaries_       │          │          │          │
 Illinois Penitentiary      │        51│      (25)│      (11)│      (36)
   (Ordahl)                 │          │          │          │
 Ohio Penitentiary (Haines) │        87│          │          │        18
 State Prison, Mass. (Rossy)│       300│          │          │        16
                            │          │          │          │
     _Reformatories_        │          │          │          │
 State Reformatory,         │       370│        13│        22│        35
   Minnesota (Green)        │          │          │          │
 State Reformatory, Iowa    │       996│        20│        15│        35
   (Report)                 │          │          │          │
                            │          │          │          │
     _Training Schools_     │          │          │          │
 Indiana Boys School        │       229│        30│        18│        48
   (Hickman)                │          │          │          │
 Boys Industrial School,    │       671│        15│        27│        42
   Ohio (Haines)            │          │          │          │
 State Industrial School,   │        50│          │          │      (18)
   Colo. (Bluemel)          │          │          │          │
 Whittier State School,     │       215│      (14)│      (18)│      (32)
   Calif. (Williams)        │          │          │          │
 State School for Boys, Ill.│       341│      (11)│      (20)│      (31)
   (Ordahl)                 │          │          │          │
 Industrial School, Mich.   │       801│         6│        15│        21
   (Crane)                  │          │          │          │
 State Industrial School, N.│       147│          │          │     (37+)
   H. (Streeter)            │          │          │          │
 Texas State Juvenile       │       296│         8│         9│        17
   Training School (Kelley) │          │          │          │
                            │          │          │          │
 COUNTY AND CITY            │          │          │          │
                            │          │          │          │
     _Jails and Workhouses_ │          │          │          │
 Repeaters in jail in a     │    50[27]│        48│        20│        68
   Virginia city (State     │          │          │          │
   Commission) Negro        │          │          │          │
 Repeaters in jail in a     │    50[27]│        36│        10│        46
   Virginia city (State     │          │          │          │
   Commission) White        │          │          │          │
 Chicago House of Correction│       335│        21│        29│        50
   (Kohs)                   │          │          │          │
 Columbus, O., Workhouse, 28│       100│      (14)│      (17)│      (31)
   Negroes (Gilliland)      │          │          │          │
                            │          │          │          │
     _Juveniles_            │          │          │          │
 Newark Detention Home, N.  │       100│          │          │    66[28]
   J. (Gifford and Goddard) │          │          │          │
 Allegheny County Juveniles │       125│    29[28]│    26[28]│    55[28]
   Detention Home, Pa.      │          │          │          │
   (Mathews)                │          │          │          │
 Boys cared for by the      │       104│        11│        17│        28
   county (Stenquist,       │          │          │          │
   Thorndike and Trabue)    │          │          │          │
   Delinquents              │          │          │          │
 Cook County Detention Home,│       337│         7│          │
   Chicago (Bronner)        │          │          │          │
 Glen Lake Farm School for  │       123│         2│         5│         7
   Boys, Hennepin County,   │          │          │          │
   Minn. (Miner)            │          │          │          │
 Probationers, Juvenile     │       100│          │          │       (6)
   Court (Bluemel)          │          │          │          │

  Parentheses indicate percentages or selection on a somewhat
  different basis.

1. Intellectual deficiency as a social problem is undoubtedly at present
most serious among women and girls who are sex offenders. It is this
fact which accounts for the excessive amount of deficiency found in the
industrial schools for girls, and the reformatories for women. It is not
necessary to repeat the discussion of the reasons for this which were
considered at the close of the studies of women delinquents. The most
closely corresponding class of male delinquents is probably the “vags,”
as Aschaffenburg suggests (_68_, p. 162). The vagrants form a much
smaller portion of the inmates of the institutions for male delinquents
than do the prostitutes in the institutions for women and girls. The
little evidence we have indicates, moreover, that as a class the
ne'er-do-wells average higher in ability than the prostitutes. They are,
probably, a more mixed group. As reported by Terman (_57_), Mr. Kollin
found among 150 “hoboes” at least 20 per cent. belonged to the “moron
grade of mental deficiency.” * * * “The above findings have been fully
paralleled by Mr. Glen Johnson and Professor Eleanor Rowland, of Reed
College, who tested 108 unemployed charity cases in Portland, Oregon”
(_57_, p. 18). Since these investigators used the Stanford Scale, the
borderline was probably set at the position where it would exclude about
1% of the ordinary population, a little more conservative than our
doubtful group. We should know more about deficiency among the typical
“Weary Willies,” since it is likely that courts are accustomed to assume
that vagrancy is a habit which can be corrected by a term in the
workhouse. There is little doubt that mental deficients fill up the
recruiting stations for the prostitutes and “vags.” It is with these
classes that the most intensive social work should be done in the
campaign for early isolation of the unfit.

2. Institutions which care for the same type of delinquents show
pronounced variation in the amount of tested deficiency. Compare the
Indiana Boys' School with the Michigan Industrial School for Boys.
Thirty per cent. tested presumably deficient in the former as against 6%
in the latter; or 48% in the former and 21% in the latter tested below
our borderline for the presumably passable intellects. This difference
can hardly be explained by errors in testing. It marks a significant
difference between the care of the mentally deficient in the two states.
The difference in the success of states in isolating their feeble-minded
is best shown by comparing the Newark and Pittsburgh institutions for
boys from the juvenile courts on the one hand, and the local groups of
boy delinquents from Hennepin County, Minn., and Cook County, Ill., on
the other. In one case over 60% and in the other less than 10% were
below the same borderline. In other words, the courts in Newark and
Pittsburgh were deliberately sending mental deficients to their local
institutions for delinquents because there was no better place
available, not because they mistook deficiency for delinquency. The
better diagnosis of deficiency by test criteria is, however, the first
step in demonstrating this situation so that public sentiment for an
adequate state care for the feeble-minded may be in accord with a
conservative statement of the present conditions. Moreover, we have made
real progress when we have demonstrated objectively that the difference
in the character of the inmates of corresponding institutions is not a
mere matter of opinion.

3. Unfortunately for social reform, a wholly incorrect impression seems
to have spread abroad that half of the delinquents in _juvenile courts_
are feeble-minded. Exaggeration of the condition retards rather than
assists a sane public policy regarding the indefinite isolation of those
demonstrably deficient by psychological tests. The mistaken impression
apparently started with the study of Goddard and Gifford as to the
condition found among boys at the Newark Detention Home. Two-thirds of
these boys tested approximately below our borderline for clearly
passable intellects. I should not be inclined seriously to question
calling these two-thirds in the Newark Home feeble-minded, since I am
willing to class those in our doubtful group as feeble-minded provided
that they are persistent delinquents. The deductions which were drawn
from this startling discovery seem, however, to have slipped into the
literature of the subject without anybody noting that they were
unjustified by the facts. In the first place the condition at Newark
Detention Home may reflect a peculiar local situation analogous to that
at Pittsburgh in which deficient boys had to be cared for in the
detention home because no other institution was available for these
feeble-minded. Under these recognized local conditions, it would seem
that the general situation might be better represented by the conditions
of deficiency found since then in Cook and Hennepin counties than by the
conditions at Newark. We at least know that Newark and Pittsburgh
represent special and not ordinary conditions among those in local
detention homes, unless the situation is very different in the East from
that in the West.

Besides regarding the condition in the Newark Detention Home as
representative of the general condition in detention homes elsewhere, it
was argued that the condition in the detention home represented the
condition among the ordinary cases of delinquents before the juvenile
courts. The groups in detention homes are undoubtedly extreme both as to
the seriousness of their delinquency and as to their deficiency. Since
Goddard published his paper following the Newark study considerable
additional evidence has been made available. But even without this
contradictory data, it was a big jump to assume that the condition in
the local detention home represented the frequency of deficiency among
the ordinary cases which come before the juvenile courts.

Either Dr. Goddard overlooked this distinction between serious offenders
who are often repeaters and the ordinary offenders, or he took the
questionable position that the difference was unimportant. On the basis
of the tests of cases in the detention home in Newark, which we have
quoted, he says that “by actual test 66% of the children in the Juvenile
Courts of Newark are feeble-minded.” Again after quoting the results of
examinations of delinquents at several _institutions_, he says: “Suppose
we take the very lowest figure that any of these studies suggests,
namely 25%, and see for a moment where it leads us. Twenty-five per
cent. of the children _who come before the Juvenile Court_[A] are
feeble-minded. The figures cannot be less than that” (_19_).

This paper was subsequently referred to by Dr. Fernald, physician at the
Massachusetts Reformatory, as follows: “It has been found by the most
eminent research workers in this field that probably not less than 25%
of the criminals who come before our courts are feeble-minded and that a
_much larger percentage of the children brought before the Juvenile
Court are defective_” (_103_).[29]

The incorrectness of the assumption that detention home cases show no
more deficiency than ordinary juvenile court cases could not at the time
be demonstrated. Since then, however, there have been several objective
studies. In Minneapolis we found that relatively twice as large a
proportion of the serious offenders sent to the county detention home
were either three or four years retarded in school as we found among the
ordinary juvenile offenders taken consecutively. The data will be
presented later under our discussion of the school test. We also found
that if we compared the results of Binet examinations at the Minnesota
reformatory (_22_) with those at the county detention home, tested
deficiency is about five times as common among the older and more
established offenders at the reformatory. At Chicago serious deficiency
was less frequent among those in the detention home than among more
serious recidivists. Bluemel, as we have also noted, found that the
frequency of tested retardation was decidedly greater among boys in
Denver sent to the State Industrial School than among those only put on
probation in that city. The investigation of Stenquist, Thorndike and
Trabue shows that serious deficiency is less among dependent boys than
among delinquents in the same county. Cornell found less truant boys
deficient than delinquent boys, in the Philadelphia House of Detention.
In Chicago, Denver and Minneapolis, moreover, less than 10% of the more
serious cases in the detention homes were found deficient. This evidence
all tends to contradict the assumption that a large proportion of the
ordinary children brought before the juvenile court is feeble-minded.

Ernest K. Coulter, as Clerk of the Children's Court of New York County,
has raised his voice in protest against charging the Juvenile Courts
with dealing mainly with feeble-minded children. He says:

“The writer, who has seen at close range 80,000 children pass through
the largest Children's Court in the world, has little patience with the
sentimentalist who would pounce on every other juvenile delinquent as a
mental defective” (_94_, p. 68).

Unless we are to convert valuable propaganda for isolating the
feeble-minded from good kindling wood into shavings, we must remove this
cloud which has been cast upon the mentality of the ordinary children
who are brought before juvenile courts of the country. Travis, (_202_)
years ago, may have been nearer right when he said that 95% of the
children who come before the Juvenile Court are normal. Surely this
agrees better with the conditions found in Chicago, Denver, and
Minneapolis. Possibly these western cities, however, show unusually good
conditions. The evidence as to the peculiar local situations in Newark
and Pittsburgh makes one confident that their detention home conditions
do not at all represent the frequency of mental deficiency among
ordinary juvenile offenders in these cities. I see nothing in the
present evidence from mental tests to indicate that the frequency of
mental deficients who might justly be sent to institutions from among
the ordinary children who come before the juvenile courts of the
country, would be over 10 per cent.

4. What shall we say as to the general frequency of deficiency among
delinquents of all classes? How about the impression that a large
proportion of them are not responsible because of their deficiency and
that the condition is worse among juveniles? Note some of the published
statements: “Probably 80% of the children in the Juvenile Courts in
Manhattan and Bronx are feeble-minded.” “Preliminary surveys have shown
that from 60% to 70% of these adolescents [sent to the industrial
schools in one state] are retarded in their mental development and are
to be classed as morons.” “Forty to 50% of our juvenile delinquents are
without a doubt feeble-minded.” “The best estimate and the result of the
most careful studies indicate that somewhere in the neighborhood of 50%
of all criminals are feeble-minded.” “Nearly half of those punished for
their wickedness are in reality paying the penalty for their stupidity.”
“More than a quarter of the children in juvenile courts are defective.”
“One-third of all delinquents are as they are because they are
feeble-minded.” “It is extremely significant in the study of juvenile
delinquency that practically one-third of our delinquent children are
actually feeble-minded.”

Fortunately, some of these writers are already beginning to qualify and
modify their views, and some of these statements misstate the idea of
the investigators, but it is difficult to correct the impression that
has been gathered from those who speak with authority. In the face of
the fact that mental deficiency is undoubtedly the most important single
factor to be considered today in the institutional care of delinquents,
one hesitates to correct even the most exaggerated impressions as to its
importance. On the other hand, it seems time to modify opinions which
raise false hopes as to solving the problem of delinquency by caring for
the feeble-minded. Above all it is important to lay a surer foundation
on which a platform for the social care of these unfortunates may be
securely built.

In the first place, it is necessary to recognize that after all the
feeble-minded are properly cared for by society the problem of the
ordinary delinquent may still remain with us in much of its present
proportions. Surely the isolation of the deficient children will hardly
scratch the surface of the problem of first offenders as it comes before
the juvenile courts of the country. To this it should be replied that
the first offenders are not, after all, the troublesome cases before our
courts. If we study the different groups of delinquents which have been
tested, we notice that they represent highly selected groups among the
ordinary offenders whether these be adults or minor delinquents. The
only parallelism which can be traced at all is between prostitutes and
vagrants and some of the institutional groups. We should stop assuming
that the institutional delinquents represent the ordinary offenders. The
present evidence points to the conclusion that it is the repeaters, not
the first offenders either in the juvenile or criminal courts, who are
most likely to be deficient. Nevertheless, 68% of the boys brought
before the Chicago Juvenile Court during its first ten years were first
offenders (_142_), while 89% of 4143 boys in the Juvenile Court in
Minneapolis were first offenders (_105_). We know almost nothing about
the frequency of deficiency among the first offenders brought before our
courts and yet the bulk of delinquents are undoubtedly first offenders.

On the other hand, the repeaters do account for a considerable portion
of the _cases_ before the courts, especially the municipal courts,
because each offender appears time and time again. In the Virginia city
cited, for example, repeaters furnished 60% of the jail commitments for
three years. This is probably also an indication of the workhouse
situation, which is best represented by such a study as that of Kohs.
The proportions of _offenses_ accounted for by deficiency would,
therefore, be much larger than the proportion of _offenders_ who are
deficient. While the offenses of repeaters might not commonly be serious
crimes, they afford a serious problem because of their bulk and because
temporary restraint is of little use when the offender is mentally weak.
As Aschaffenburg says: “We must not forget that it is not the murderers,
not the swindlers, on a large scale, not the assassins of people in high
places, and not the sexual murderers, that determine the criminal
physiognomy of our day, but the thieves and pickpockets, the swindlers
and abusers of children, the tramps and the prostitutes” (_68_, p. 181).

The best that we can do is to study Table XI, which gives us a
classified list of different types of delinquents in institutions. If we
should pick out in it such institutions as represent to us the typical
conditions in the country we could get an idea of what we might expect
from groups of offenders of each type. For example, we might say that
the Massachusetts State prison is typical of such institutions, and it
contained possibly 16% who were deficient. Picking the Ohio Boys
Industrial School as typical of its class, it had between 15% and 42%
deficient, depending on how conservative you wish to be in your
diagnosis. So one might go through the list stating the expectation for
each type of institutional delinquent. If these were then weighted
according to the number of delinquents of each class in the country sent
to them, we would have some idea of the frequency of deficiency among
those who reach the institutions. Merely to average the columns in Table
XI would give only a false impression. The seriousness of the situation
is amply demonstrated among repeaters and the inmates of certain
institutions. Each superintendent should be put upon inquiry as to his
own charges.

Nothing which I have said in caution as to the importance of deficiency
in solving the problem of delinquency can be taken for a moment to
signify that the effort for the isolation of the deficient is misspent.
Elimination of a generation of deficients will not solve the problem of
delinquency, but in no other way is there open such a clear and definite
method of reducing that problem. The better care and prevented
procreation of even a tenth of the delinquents who would propagate
deficiency, would mean the most scientific advance in attacking the
problem of delinquency. A safe public policy can be formulated which
would at first provide for appropriate permanent care of at least that
number of delinquents in institutions who by test are presumably
deficient. This perfectly obvious first step promises to tax our
facilities for years.


Footnote 14:

  During the months when these examinations were made we failed to test
  six boys, four of whom were sent to relatives outside of the state.
  One other could not be tested because of his unfamiliarity with the
  English language.

Footnote 15:

  Louise Ordahl and George Ordahl. A Study of 49 Female Convicts.
  Journal of Delinquency, 1917, _2_, 331-351.

Footnote 16:

  Eugenics and Social Welfare Bulletin No. XI, 1917, p. 73.

Footnote 17:

  Grace M. Fernald. Report of the Psychological Work at the California
  School for Girls. J. of Delinquency, 1916, _1_, 22-32.

Footnote 18:

  Ordahl, Louise E. and George. A Study of Delinquent and Dependent
  Girls. J. of Delinquency, 1918, III, 41-73.

Footnote 19:

  Jean Weidensall. The Mentality of the Unmarried Mother. National
  Conference of Social Work, 1917.

Footnote 20:

  J. of Deficiency, 1918, III, 1-11.

Footnote 21:

  George Ordahl. A Study of Fifty-Three Male Convicts. J. of
  Delinquency, 1916, _1_, 1-21.

Footnote 22:

  M. L. Beanblossom. Mental Examination of Two Thousand Delinquent Boys
  and Young Men. Indiana Reformatory Print, 1916, p. 23.

Footnote 23:

  Bull. No. 1713, University of Texas, 1917, p. 125.

Footnote 24:

  A. R. Gilliland. The Mental Ability of One Hundred Inmates of the
  Columbus, (O.) Workhouse. J. of Crim. Law and Crim., 1917, _7_, pp.

Footnote 25:

  R. Pintner. One Hundred Juvenile Delinquents Tested by the Binet
  Scale. Ped. Sem., 1914, XXI, 523-531.

Footnote 26:

  George Ordahl. Mental Defectives and the Juvenile Court. J. of
  Delinquency, 1917, II, 1-13.

Footnote 27:

  Both sexes.

Footnote 28:

  Local conditions explain the excessive amount of deficiency.

Footnote 29:

  Italics mine.


The Binet scale in its various forms provides only part of the objective
evidence as to the mental inferiority of delinquents, although it
affords the best means at present of interpreting the borderline of
deficiency. Among the other investigations in which psychological tests
have been tried with delinquents in comparison with normal subjects, the
recent study of the Mentality of the Criminal Women by Weidensall is the
most important so far as estimating the frequency of deficiency is
concerned (_60_). It affords an admirable check upon our conclusions
from the Binet examinations, since she gives in detail the results with
a random group of 88 women inmates of the Bedford (N. Y.) Reformatory,
which is quite comparable with the group of 200 which she tested with
the Binet scale, and which we have already considered.

For our purpose, the most important comparisons are those between the
group of women in the reformatory and the group of 15-year-old
Cincinnati working girls tested by Woolley with the same tests.
Weidensall's Table 92 shows for three tests the percentages of the
Bedford women who tested below the lowest 1% of these girls. For the
opposites test, 20% were below this borderline; for a test on the
completion of sentences, 12%; for the memory span for digits, 29%. She
also shows that 17% of the delinquent group were poorer than any of the
working girls and 30.7% as poor as the poorest 5.7% of these working
girls, when their mentality is measured by the number of the tests in
which their ability is at or above that of the median working girl of
fifteen. This 30.7% is probably most nearly comparable in ability with
the lowest 0.5% of the general population.

Kelley's monograph on Mental Aspects of Delinquency, to which reference
was made in the last chapter, gives the results with boys in the Texas
Juvenile Training School for the completion test and his own
construction test, as well as for a number of physical measurements,
sensory and motor tests. He has used various data from which to provide
norms for comparison. In connection with the Psychopathic Institute at
the Chicago Juvenile Court, Healy and Fernald (_125_) have published an
elaborate series of tests with suggestions as to how they may be
employed for analyzing a child's mental ability and estimating his
mental capacity. Schmidt has partially standardized these tests (_178_).
Guy G. Fernald (_15_) tried out a dozen different tests and recommends
seven of them for testing delinquents who are of adolescent age or
older. Haines has sought the diagnostic value with girl delinquents of a
dozen tests including Fernald's test of moral judgment. Weidensall
(_218_), Smedley (_51_), Rowland (_49_), Porteus (_45_), and Whipple and
Fraser (_220_, p. 663), have published results with certain tests tried
with delinquents. With none of these tests can we adequately define the
borderline of feeble-minded intellects.

There is no series of tests which has been employed outside the field of
delinquency which diagnoses the borderline cases objectively so well as
the Binet scale. The tests of Weyandt (_219_), Rossolimo (_175_),
Rybakow (_176_), and Knox (_134_) are without definable limits based on
unselected groups. Those employed by Dr. Norsworthy, while
scientifically better scored for describing the borderline, were not
arranged with this in view (_160_). Carpenter has published norms
obtained with Squire's tests on 50 pupils of each age from 7 to 14.
Single tests like the form board (_87_), Knox's cube test (_134_), the
substitution test (_1_), and the A test (_160_) have been tried with
delinquent or feeble-minded groups as well as with normal people. Under
the direction of the New York Board of Charities an excellent beginning
has been made in determining norms for eleven different tests (_158_).
Stenquist, Thorndike and Trabue (_54_) have furnished developmental
norms for several tests. Gilbert (_108_) and Smedley (_51_) at an
earlier date provided age norms and deviations for certain tests. Mrs.
Woolley has provided the percentile distribution for a series of mental
and physical tests with 14-and 15-year-old children leaving the public
schools to go to work (_222_) (_223_). In England a goodly number of
different tests have been tried out on small groups or on children of
particular ages (_84_) (_63_) (_224_). Pyle has obtained norms and
variations with a series of group tests. It approaches nearest to the
Binet as a developmental scale for the immature, but these tests have
not been tried as individual tests and so could hardly be used safely
for individual diagnosis. A graphic summary of the developmental curves
for most of these tests on children will be found in Chapter XIII.

In no case do we find any tests except the Binet scales which have
reached a stage of practical usefulness for the diagnosis of deficiency
except as supplementary aids for checking the Binet indication with
children of particular ages. The emphasis has almost universally been
placed on determining the central tendencies of children of different
ages and not on the lower limits of the distributions. Considering
mental tests apart from the Binet scale, in all the extended literature
which has been brought together in books like Whipple's Manual of Mental
Tests (_220_), one may seek in vain for tests which have reached the
position of defining the limits of serious mental deficiency. This
indicates, of course, the difficulty as well as the newness of the
problem, although the quantity of work that is being done shows the
great interest aroused. From all of this mass of research on mental
tests one may gather much that is useful in analyzing the character of a
mental defect. Many of the tests admirably aid in elaborating the
subjective impression of the examiner. The failure to do this
systematically has been one of the main criticisms raised against the
Binet scale. This and the incorrectness of the borderline described in
the published scale seem to be the main objections made by Miss Schmidt
to the Binet Method. She voiced the objection of the Juvenile
Psychopathic Institute in Chicago to the tests as follows: “It has been
the experience of the writer, and it may be added of all others who have
worked in this laboratory, where practical results are demanded, that
the Binet tests cannot furnish an adequate means through which to come
to conclusions for the disposition, classification, or treatment of the
cases which come for diagnosis” (_179_).

Dr. Merrill of the Seattle court also seems unfriendly to the Binet
scale when he says: “Any system of tests by which _alone_[30] it is
attempted to classify the child as being of a given mental age involves
the fallacy of pseudo-exactness, and needs carefully to be avoided”
(_148_). Nobody would seriously urge that real exactness of definition
leads to confusion. It is just the looseness of definition of borderline
with the Binet Scale which has led to most of the mistakes with it.
Perhaps Dr. Merrill has not discovered that the scale works just as well
when used as a graded series of tests without the designation of mental
ages at all. The latter is merely a convenience. On the other hand, we
should agree when he says, that “no scale of tests can give a valid
measure of the child's intelligence unless supplemented by a
consideration of his history,” especially if he includes in the child's
history a medical diagnosis.

The objection that the Binet tests do not analyze the source of the
child's mental defect is of course important if one were considering
whether a better scale might not be devised. It is rather beside the
point, however, when one remembers that it is not the purpose of this
scale to determine the causes of deficiency, but only to say whether a
deficiency in general intelligence is present and to what degree. The
causes of the disturbance must then be determined by an expert.
Moreover, if one classifies the Binet tests as Meumann has done one may
often get valuable clues as to whether the deficiency is mainly in
information or in mental process. In seeking the causes of the
disturbance, the expert should not overlook the standardization of the
Rosanoff and Kent Association Test which has been available for
delinquent, feeble-minded and normal children (_174_). It is one of the
most important supplementary means for mental analysis which has yet
been standardized for practical use. The most complete tables on
children's reactions for this test have been published in a
_Psychological Monograph_ by Woodrow and Lowell.

The importance of more accurate psychological tests in studying mental
disturbance is well illustrated by comparing the results that may be
obtained with the Binet tests with the desultory, unstandardized tests
such as one finds in Dr. Schaefer's Allgemeine gerichtliche Psychiatrie
für Juristen, Mediziner, and Pädagogen (_177_), or Dr. Cimbal's
Taschenbuch (_91_) prepared for physicians and jurists. Suggestive as
these books are for disclosing different mental activities, they give no
means of evaluating the disclosures. They show the puerile stage in
diagnosis which had been reached before standardized tests were

Among those who are engaged in practical clinical work for determining
mental development the Binet Scale has advocates who are quite as ardent
as critics we have noted. Goddard, Kuhlmann (_139_), Wallin (_213_), and
Towne (_201_), have all used it in the practical examination of hundreds
of cases and heartily commend its use in connection with delinquents, as
does Healy for the earlier ages (_27_, p. 80). On the other hand there
is a growing sentiment that the examinations should only be entrusted to
experts in mental development. It is felt that the physician who has not
had enough training in a psychological laboratory to understand the
snares of mental tests, and very few have had this opportunity, ought to
refer this question to a clinical psychologist as the best physicians
now do when such experts are available. Perhaps nobody is so well
equipped to judge a child's mental development without diagnostic tests
as his school teacher, although Terman has shown that the teacher's
judgment may be seriously at fault when he has not learned to dissociate
mental capacity from the age and size of the child (_196_). In an
editorial in the Journal of Criminology, Dr. Gault (_106_, p. 322)
expresses the opinion that “dissatisfaction with mental tests as a means
of diagnosis” is traceable to the fact “that what the lay mind
recognizes as palpable errors are often made by half-trained
'investigators,' 'research directors' and even by men and women whose
only qualification is that they have been trained for six weeks in a
psychological clinic.” Dr. Wallin demands that the tests should be used
for diagnosis only by the psychologist with clinical experience.

The American Psychological Association has cautioned against diagnosis
by those inadequately trained and adopted the following resolution at
its 1915 meeting:

  “Whereas, psychological diagnosis requires thorough technical
  training in all phases of mental testing, thorough acquaintance with
  the facts of mental development and with the various degrees of
  mental retardation.

  “And whereas, there is evident tendency to appoint for this work
  persons whose training in clinical psychology and acquaintance with
  genetic and educational psychology are inadequate:

  “Be it resolved, that this Association discourages the use of mental
  tests for practical psychological diagnosis by individuals
  psychologically unqualified for the work.”

Binet's suggestion as to the diagnosis of mental development seems to be
best. He says that “the selection of defectives calls for three
varieties of experience—that of teachers, of doctors, and of
psychologists” (_77_, p. 38). These three points of view may be combined
in a committee as in France, or the decision may rest with a specialist
in mental development whose judgment should only be given after he has
all the information which the medical, educational, and social diagnosis
can provide to supplement his test records and his evaluation of the
causes of the condition found.

Those who are considering the legal isolation of the feeble-minded,
especially defective delinquents, and superintendents who wish a safe
rule for transferring school children to special classes or schools for
the mentally retarded should keep a committee plan in mind. A legal
requirement embodying an examination by such a commission could easily
be framed. In my opinion the expert in mental development should be
required at least to have the equivalent of a year of graduate work with
his major time in testing. On the other hand very desirable information
as to children that require examination may be obtained by a teacher who
uses a mental scale intelligently. In the hands of an amateur it may
perform an analogous service to that of a vision chart in discovering
children who require expert examination of their eyes. The danger lies
in the novice not knowing his limitations. Few who have had experience
with tests can doubt, however, the much greater danger of inadequate
diagnosis of mental development on the part of physicians who give
opinions about mental deficiency without having had experience with test


Footnote 30:

  Italics mine.


                           A. IN MINNEAPOLIS

Besides the estimates of deficiency based on tests, the school records
may furnish valuable objective evidence about mental retardation among
delinquents. The school environment is the first prominent social
environment to which the child must adjust himself. If he fails in this
while in regular attendance we have an important indication of mental
deficiency. With laws which require attendance at school, we may even
estimate the mental character of groups, on the basis of success in
school, provided that we use proper caution as to the effects of late
entrance and of absence from school. Moreover, whether retardation in
school shows mental deficiency or not, it certainly sets forth a vital
problem in connection with delinquency. We shall first consider the
school retardation of delinquents and leave the problem of checking the
tests by school records until later.

In order to study school retardation we tabulated the school position of
236 boys and 95 girls consecutively found delinquent in the Minneapolis
juvenile court. To make the results more significant we did not include
any cases dismissed at their hearing in court. Comparison with more
serious delinquents is made by means of the group of 100 juvenile
repeaters and 123 from the Glen Lake Farm School. The school position
and actual age of each delinquent was compared with the age and grade
distribution among Minneapolis elementary school children. The latter
was determined by a census made the same year the returns for which
included about 15,000 of each sex (see Table XII).[31] The ages and
grades were recorded for the beginning of September, when the school
year opens, and the census was taken late in the year after all the
children had been registered in school. That different groups can only
be properly compared when the age-grade distributions are made for the
same time in the year is clear when one remembers that the ages are
changing throughout the school year while the grades remain the same for
at least half the year. The census was taken for another purpose so that
it unfortunately does not include the high school pupils. Since the
frequency and amount of retardation increases for older ages which occur
relatively more frequently in the groups of delinquents the comparison
somewhat exaggerates the difference between the groups. This difference
in the relative ages of the groups is allowed for, however, in a later
table on which the discussion will be based. The school positions of the
various groups of delinquents and of ordinary school children are given
in Table XIII and graphically in Figure 2.

                               TABLE XII.

                         SCHOOLS OF MINNEAPOLIS


     │                               _Ages_
 Gra-│ 5│   6│   7│   8│   9│  10│  11│  12│  13│  14│ 15│ 16│17│18+│ To-
 des │  │    │    │    │    │    │    │    │    │    │   │   │  │   │tals
    I│61│1656│ 629│ 144│  44│   7│   4│   4│   4│    │  2│   │  │  1│ 2556
   II│ 1│ 151│ 979│ 650│ 221│  92│  28│  11│   4│   2│  1│   │  │   │ 2140
  III│  │  12│ 169│ 724│ 606│ 290│ 106│  44│   9│  10│  4│  3│  │  2│ 2140
   IV│  │    │    │ 140│ 628│ 635│ 344│ 184│  66│  34│ 13│  2│  │   │ 2046
    V│  │    │    │   2│ 120│ 489│ 541│ 371│ 190│  88│ 36│  9│ 1│   │ 1847
   VI│  │    │    │    │   5│  94│ 428│ 594│ 380│ 223│ 96│ 20│ 1│  1│ 1842
  VII│  │    │    │    │    │   7│  97│ 422│ 458│ 397│204│ 60│ 6│  2│ 1635
 VIII│  │    │    │    │    │    │    │ 112│ 308│ 499│346│142│27│  6│ 1444
     │62│1819│1777│1650│1624│1614│1552│1742│1419│1235│702│236│45│ 12│15489


     │                               _Ages_
 Gra-│ 5│   6│   7│   8│   9│  10│  11│  12│  13│  14│ 15│ 16│17│18+│ To-
 des │  │    │    │    │    │    │    │    │    │    │   │   │  │   │tals
    I│45│1642│ 493│ 117│  38│   9│   6│   3│   1│   1│  1│   │  │  1│ 2356
   II│  │ 143│ 890│ 582│ 159│  63│  27│   6│   5│   1│  1│   │  │   │ 1877
  III│  │  10│ 165│ 755│ 553│ 193│  77│  27│  12│   4│   │   │  │   │ 1796
   IV│  │    │   6│ 168│ 727│ 618│ 290│ 132│ 446│  18│  8│   │  │  1│ 2014
    V│  │    │    │  12│ 133│ 573│ 611│ 309│ 131│  44│ 15│  4│  │  1│ 1833
   VI│  │    │    │    │   7│ 132│ 493│ 519│ 330│ 179│ 80│ 17│ 1│  3│ 1761
  VII│  │    │    │    │    │   6│ 113│ 447│ 554│ 342│173│ 29│ 5│  2│ 1671
 VIII│  │    │    │    │    │    │   6│ 109│ 432│ 577│348│ 96│12│  8│ 1588
     │45│1795│1554│1634│1617│1594│1623│1552│1510│1166│626│146│18│ 16│14896

                              TABLE XIII.


      │             │      Summary       │      Percentages      │
      │    BOYS     │Number│ Retardation │Advanced │Satisfactory │
      │             │      │ Per  │ Av.  │ 2  │ 1  │      │      │
      │             │      │ Cent │ Am't │    │    │      │      │
      │Ordinary     │ 15489│    70│  0.37│ 0.2│ 6.1│  36.3│  30.0│
      │  pupils     │      │      │   Yr.│    │    │      │      │
      │             │      │      │      │    │    │      │      │
      │Ordinary     │   236│    27│  1.34│ 2.5│ 9.7│  17.4│  30.1│
      │  delinquents│      │      │   Yr.│    │    │      │      │
      │             │      │      │      │    │    │      │      │
      │Recidivists  │   100│    74│  1.77│ 1.0│ 1.0│   6.0│  18.0│
      │             │      │      │   Yr.│    │    │      │      │
      │             │      │      │      │    │    │      │      │
      │County Farm  │   123│    68│  1.66│    │ 0.8│  13.8│  17.1│
      │  School     │      │      │   Yr.│    │    │      │      │
      │             │      │      │      │    │    │      │      │
      │    GIRLS    │      │      │      │    │    │      │      │
      │             │      │      │      │    │    │      │      │
      │Ordinary     │ 14879│    23│  0.27│ 0.3│ 6.8│  40.0│  30.2│
      │  Pupils     │      │      │   Yr.│    │    │      │      │
      │             │      │      │      │    │    │      │      │
      │Ordinary     │    95│    91│  2.57│ 1.1│ 0.0│   2.1│   5.3│
      │  Delinquents│      │      │   Yr.│    │    │      │      │
      │             │              Percentages              │
      │    BOYS     │               Retarded                │
      │             │ 1  │ 2  │ 3  │ 4  │ 5 │ 6 │ 7 │ 8 │ 9 │
      │             │    │    │    │    │   │   │   │   │   │
      │Ordinary     │15.9│ 7.6│ 2.7│ 1.2│   │   │   │   │   │
      │  pupils     │    │    │    │    │   │   │   │   │   │
      │             │    │    │    │    │   │   │   │   │   │
      │Ordinary     │24.6│ 9.7│ 3.4│ 1.3│0.9│   │   │   │0.4│
      │  delinquents│    │    │    │    │   │   │   │   │   │
      │             │    │    │    │    │   │   │   │   │   │
      │Recidivists  │17.0│25.0│18.0│11.0│3.0│   │   │   │   │
      │             │    │    │    │    │   │   │   │   │   │
      │             │    │    │    │    │   │   │   │   │   │
      │County Farm  │22.8│21.1│15.4│ 5.7│3.3│   │   │   │   │
      │  School     │    │    │    │    │   │   │   │   │   │
      │             │    │    │    │    │   │   │   │   │   │
      │    GIRLS    │    │    │    │    │   │   │   │   │   │
      │             │    │    │    │    │   │   │   │   │   │
      │Ordinary     │14.0│ 5.9│ 1.8│  0.│   │   │   │   │   │
      │  Pupils     │    │    │    │    │   │   │   │   │   │
      │             │    │    │    │    │   │   │   │   │   │
      │Ordinary     │15.8│32.6│20.0│ 8.4│9.4│1.1│2.1│2.1│   │
      │  Delinquents│    │    │    │    │   │   │   │   │   │

[Illustration: FIG. 2. _School Retardation of Minneapolis Delinquents
Compared With Elementary School Boys._]

In the Minneapolis group of elementary school children it will be found
that there is about as much chance of a child being in either of the two
most common ages for a grade. Among the boys, for example, 36% were in
the series represented by age 6 in the first grade, 7 in the second
grade, 8 in the third grade, etc., while 30% were in the series
represented by one year older for each grade. It is, therefore,
reasonable to regard either 6 or 7 as a satisfactory age in the first
grade, 7 or 8 in the second, when one estimates the amount of
retardation in this group. The allowance of two ages as satisfactory for
a grade is in conformity with the practise of Strayer (_189_). The
necessity of taking these ages at either the beginning or the end of the
school year, and not merely “in the grade,” is emphasized by the report
of the New York City Committee on School Inquiry (_72_). Ayres (_71_)
also considers only those pupils over-age who are over 7 in the first
grade, 8 in the second, etc., so that this may be regarded as fairly
well established as a standard for measuring the retardation in school
position of groups of children.

The summary of results in Table XIII shows that 70% of the ordinary
delinquent boys were retarded in school position as compared with 27%
among the Minneapolis boys in the elementary schools, 91% of the
ordinary delinquent girls as compared with 23% of the Minneapolis girls
of these schools. When one compares the age distribution of the
delinquent groups, given in Table XIII with that of the Minneapolis
school children in Table XII, it is clear that an allowance should be
made for the much larger proportion of older children in the delinquent
groups. This may be done by determining the percentage retarded at each
age and in each group and then calculating indices of retardation by
weighting the percentage retarded at each age in the proportion to the
number of delinquents at that age. Table XIV gives these results for the
ages 8 to 15 inclusive.

For example, in calculating the indices 39 and 70 for the frequency of
retardation among ordinary delinquent boys as compared with elementary
school boys, the percentages retarded at each life-age for each of these
groups was multiplied by the number of ordinary delinquent boys at this
age, as shown lower in the table, and the totals divided by the number
of ordinary delinquents, 213. The average frequency of the retardation
of a school group which compares in ages with the delinquent group was
thus determined. In calculating the indices of amount of retardation the
same procedure is followed except that the average number of years
retarded is found for each age and this is multiplied by the number of
delinquents at that age. The 16-year-olds are omitted because of the
inadequacy of the school census for this age. According to the standard
which regards 7 years as satisfactory in the first grade there can be no
retardation under eight years of age. Since some of the pupils 13 years
of age and over have reached high school and so do not show in the
Minneapolis table the percentage of retardation for children 13-15 years
is based on the assumption that the number of children at these ages
will be the same as the average number for 11 and 12 years. No credit
could be allowed for those advanced in school positions on account of
the incompleteness of the Minneapolis census for older ages. The
comparison is, therefore, on the basis of retardation alone.

                               TABLE XIV.

                          CORRESPONDING AGES.

   (_Age 7 or younger regarded as satisfactory in the first grade._)

                     │                   RETARDATION
                     │       Percentage Retarded at Each Life-Age
                     │  Index   │ 8  │ 9  │ 10 │ 11 │ 12 │ 13 │ 14 │ 15
 School Boys         │     =39%=│   8│  16│  24│  31│  35│  40│  45│  43
 Delinquent Boys     │     =70%=│   0│  44│  50│  67│  58│  60│  77│  93
 School Boys         │     =36%=│    │    │    │    │    │    │    │
 Glen Lake Boys      │     =86%=│    │  17│  50│  46│  66│  81│  61│  87
 School Girls        │     =35%=│   7│  12│  16│  25│  31│  33│  37│  93
 Delinquent Girls    │     =90%=│   0│ 100│  50│  50│  75│  83│  95│ 100
                     │  Index   │Average Amount of Retardation in Years
 School Boys         │ =.61 Yr.=│ .09│ .19│ .31│ .43│ .54│ .63│ .78│ .64
 Delinquent Boys     │=1.27 Yr.=│ .00│ .66│ .50│ .86│1.09│1.11│1.23│2.11
 School Boys         │ =.54 Yr.=│    │    │    │    │    │    │    │
 Glen Lake Boys      │=1.54 Yr.=│    │ .17│ .50│ .62│1.25│1.86│2.11│2.03
 School Girls        │ =.64 Yr.=│ .07│ .15│ .22│ .34│ .45│ .50│ .59│ .82
 Delinquent Girls    │=2.29 Yr.=│ .00│1.00│1.00│1.00│1.25│2.25│2.05│2.84
                     │  Totals  │  Number of Children at Each Life-Age
 School Boys         │    13,123│1650│1624│1614│1552│1742│1647│1647│1647
 Delinquent Boys     │       213│   3│   9│   6│  21│  25│  47│  56│  46
 Glen Lake Boys      │       108│   0│   6│   8│  13│  12│  21│  18│  30
 School Girls        │    12,781│1634│1617│1594│1623│1552│1587│1587│1587
 Delinquent Girls    │        82│   2│   1│   2│   2│   4│  12│  21│ 338

  Index equals the sum of retardation at each age multiplied by the
  number of delinquents at that age divided by the total number of

From the indices of frequency of retardation in Table XIV it will be
seen that retardation of one or more years below the standard of age 7
in the first grade is nearly twice as common among the ordinary
delinquent boys as among a group of school boys of corresponding ages,
while it is fully 2½ times as great among the ordinary girl delinquents
as among a corresponding group of school girls, when estimated on the
same basis.

To understand the significance of this comparison one should consider
the relative difference which is shown between school children and
delinquents in the statistics of health, defective sight, nose and
throat obstructions, etc. The percentages of consecutive delinquents
showing other defective or diseased conditions has never, so far as the
writer is aware, been found to be double that among the school children
generally when figured on a corresponding basis. Medical inspection
shows that for other conditions than retardation the frequency of
defects and disease found among representative groups of ordinary
juvenile delinquents can often be equaled in the poorer schools of the
city. To find a factor relatively twice as common among delinquents as
among school children, when the frequencies are as great as with
retardation, means a variation that is unquestionably significant. This
is, of course, not an argument against the detection and treatment of
handicaps that can be benefited by the physician. It only suggests the
relative size of the two problems.

In considering the frequency of school retardation among delinquents in
Minneapolis, it will be noted that the most serious condition is clearly
among the girls, 90% of whom are below grade as compared with the index
of 35% for the corresponding group of school girls.

One may estimate that the chance of a Minneapolis boy who is retarded in
school getting into juvenile court is about 3½ times that of a boy who
is up-to-grade. But the chance of a girl who is retarded in school
getting into juvenile court is about 17 times as great as that of a girl
who is up to grade. This calculation is easily made on the assumption
that the indices of Table XIV are typical for a single year, knowing
that about 194 in 10,000 school boys in Minneapolis get into the court
annually and 21 in 10,000 school girls.

The best measure of the difference in school attainment cannot be shown,
however, without considering the _amounts_ instead of the frequency of
retardation in the groups compared. We should regard two years
retardation as twice as serious as one year and make a corresponding
allowance for each additional year of retardation. Thus weighting our
results we find in the indices of Table XIV that the boys 8-15 years of
age in the Glen Lake Farm School group of delinquents have on the
average lost 1.54 of a year through retardation in school attainment
compared with the satisfactory standard of 7 in the first grade. The
ordinary delinquent boys have lost on the average 1.27 of a year, while
the indices for Minneapolis school boys of corresponding ages are—.54
and—.61 of a year respectively. Among the ordinary delinquent girls the
average amount of retardation on the same basis is 2.29 years as
compared with .64 of a year among the school girls of corresponding age

The indices for the amount of school retardation are the most
significant figures in any of these tables, although they are based on
too few numbers to afford more than rough comparisons. It is, however, a
fairly reliable estimate to say that retardation in school attainment in
Minneapolis is about twice as great among ordinary delinquent boys and
among the detention home group while it is three times as great among
ordinary delinquent girls as among corresponding groups of elementary
school children. If we had been able to credit the groups with those in
advance of the expected position for their ages the difference would
have been even greater.


In view of the fact that retardation in school offers an important check
upon the question of the frequency of mental deficiency among groups,
besides stating a different training problem of its own, it is curious
that it has not been more systematically studied in connection with
delinquency. Few investigations include any reference to the question.
Auden (_69_) reports that among 263 committed to Borstal institutions
(juvenile reformatories) in England for the year ending March 31, 1909,
71% (_186_) had not reached the fourth standard, corresponding to the
fourth school grade. These were delinquents between 16 and 21 years of
age. The next year 402 out of 554 (72%) had not reached the fourth
grade. Not one person had reached the eighth grade and only 13 the
seventh grade. In the Minneapolis detention home group only 23 out of
the 103 over ten years of age were below the fourth grade.

Cornell gives the distribution of 236 boys in special disciplinary
classes of two Philadelphia schools (_93_). These classes are for truant
and difficult boys 8 to 14 years of age inclusive. While they are not
technically delinquents the problem is similar and they show even more
serious school retardation than the Minneapolis group. Summarizing his
results according to the standard which counts ages six or seven as
satisfactory in the first grade, and so on, we find 12.3% satisfactory;
12.3% retarded one year; 26.7% retarded two years; 30.1% retarded three
years; 15.8% retarded four years; 2.5% retarded 5 years; and 0.4%
retarded 6 years. Eighty-eight per cent. are thus behind a satisfactory
position in the grades, and 48.8% three or more years behind. This is to
be compared with 70 and 16% among ordinary Minneapolis delinquent boys
(Table XIII).

Among 647 prostitutes at the Bedford (N. Y.) Reformatory 48% either
could not read or write any language or had not finished the primary
grades. Seven per cent. had graduated from the grammar grades. Among 610
prostitutes in other reformatories reported in the same work, only 23%
had finished the fifth grade. Among 877 street cases from which
information was obtained 814 had no more education than ability to read
and write, 53 had graduated from the grammar grades or had some special
education (_133_). Another report by Weidensall we shall consider in the
next chapter.

The attending physician (_60_) of the Morals Court in Chicago inquired
“of as many of the defendants as she could, who were charged with being
public prostitutes, as to what ages they had left school.” Among 3546
cases which passed before the court in seven months the report covers
494 cases. Of these only 17 had gone beyond the fifth grade in school,
only one was a high school graduate (_161_). Among 100 girls at the Ohio
Industrial School, 11 to 18 years of age, median age 15 years, 50% were
in the third or fourth grade and 54% had failed of promotion three or
more times (_55_).

Drucker gives the age-grade distribution of 100 randomly selected minor
offenders, 15 to 22 years of age, in the Cook County (Ill.) jail. This
shows that 41 of these were below the eighth grade and three or more
years retarded at the age they left school. They might well be examined
for deficiency. Among 86 who left school at 14 or after, 24 were in the
fifth grade or below (_101_). Among 100 consecutive admissions to the
Ohio State Girls Industrial Home, Renz reports 25% in the third grade
and 25% in the fourth grade, 15% in the fifth grade; 29% failed of
promotion 4.5 to 6 years and 25% more failed of promotion 3 years
(_47_). Storer reports on the same groups (_55_). Bluemel finds that 100
probationers in the Denver Juvenile Court were retarded in school 2
years on the average as compared with an average school retardation
among the school boys of Denver of 1 year (_2_). At the New Jersey State
Home for Girls among a group of 163 selected cases 102 had not reached
the fifth grade although their average age was 17 (_12_).

The school distributions by age is given for 215 delinquents in the
California State School at Whittier for boys by Williams (_62_) in
sufficient detail to make it usable for estimating the frequency of
deficiency on a plan we shall consider shortly. Regarding age seven as
satisfactory for the first grade, and so on, only 7 of these boys had
reached this standard. Supposing that those older should have attained
at least the grade which is satisfactory for the 14-year-old, and those
younger the corresponding grades, we find that 29% were four or more
years below this standard and 14% were five years below this standard.
In the next section we shall endeavor to find out how the school records
might also be used as symptomatic of mental capacity.


Footnote 31:

  The tables of Minneapolis school children were prepared by Mr. Andrew
  J. Lein and of delinquents by Miss Lydia B. Christ, to whom I am much


There has been considerable discussion of the question whether
psychological testing should be expected to conform to the ranking of
pupils in school. This discussion however, does not attack the question
in which we are especially interested, _i. e._, how to get the best
information from both. If the school level were measured by the
_progress_ made in school by passable work and not by the school
_position_ attained often merely through age or size, Binet would be
right in expecting that in general they would correspond among groups of
children in the public schools. Agreement with real school progress
could, therefore, be taken as a criterion of a good series of tests, as
it has been by Binet and Bobertag. On the other hand Meumann and Abelson
were right in objecting to the proof of the value of tests by agreement
with the school level, if they limited their objection to tests applied
to exceptional children and to using school _position_ as a final test
of school level. Lack of correspondence with our group of delinquents
is, of course, no indication of a weakness in the Binet scale. In
numerous instances they had been promoted in school because of age
without doing passable work. The reader should also see the evidence of
the teacher's bad judgment of a pupil's ability assembled by Terman and
by Terman and Knollen (_196_).

Terman has calculated the correlation between intelligence quotients
determined by the Binet scale and the teacher's estimates of scholastic
or of general ability. These gave coefficients of .48 and .45. Doll has
found for Goddard's data on school children that the correlation of
school grades is closer with life-age than with test-age, .84 as
compared with .73 (_12_). This indicates an influence of life-age upon
promotion. In a school for deficients Burt found the correlation of
teachers' estimates with Binet ages was .55, with mental retardation or
excess .59, with intellectual quotient .48. He quotes McIntyre and
Rogers as finding coefficients about .5 for similar calculations with
normal school children in Scotland (_85_). Starch has shown that
measured by the combined ability in reading, writing and spelling a
third of the pupils are in a grade behind and a third are in a grade
ahead of their ability (_186_).

However much we might disagree as to how close a correlation might be
expected between the Binet tests and school level, independent of the
relation to life-ages, or which is the better test, it is certain that
they afford two different symptoms of mental deficiency. It becomes our
immediate problem, therefore, to discover how the most information may
be gained from a careful interpretation of the test of school level. If
we had sufficient data, three sorts of checks might be formulated. 1.
What amount of school retardation will give us the best estimate of
mental deficiency among groups? 2. What amount of school retardation
should put an individual's mentality in question so that he should be
examined? 3. What amount of school success should put in question a
Binet diagnosis?



We shall first take up the question of utilizing information about
school retardation in estimating the frequency of mental deficiency
among groups of delinquents. It is perfectly clear that retardation in
school position is not always an indication of mental retardation. A
child may be behind the position in school reached by the children of
his age merely because he has not attended school so long as his
companions. A census of school progress which we took in Minnesota
indicates that in general a large part, perhaps half, of the retardation
in school is to be thus explained even under compulsory attendance laws.
Some allowance is also to be made for physical handicaps, such as
defects of sight and hearing which are not corrected, illness which does
not cause prolonged absence, frequent change of schools, bad home
conditions, etc. Aside from absence, however, there can be no question
that greater or less degrees of mental retardation is the main cause of
retardation in school. Moreover a dull mind is often the reason for
beginning school at an older age and for staying away from an unsuitable
school environment as much as the law will permit. In any particular
case, it is to be noted, however, that all of the excuses for
backwardness in school are not likely to account for more than one or
two years of lagging for other reasons than dullness.

We cannot hope at present to get nearly so accurate a judgment about the
frequency of deficiency in groups by means of any school test as by the
psychological tests. Nevertheless, I believe that it may furnish us some
supplementary evidence. The main difficulty in formulating any general
rule for interpretation of the school level is that very different plans
of promotion prevail in different school systems. It is not uncommon,
for example, to find that a child will be promoted to a higher grade
regardless of his ability provided that he has spent two years with the
same teacher. This practise, of course, makes it impossible to judge a
particular individual's ability by the school grade he has attained
without knowing how he reached it. Nevertheless, spending two years in
each grade will begin to show in a general distribution of pupils by the
time we deal with 12-year-olds. I have gone over the tables of school
retardation of pupils provided by Strayer for several hundred cities in
the United States and I find that the percentage method of approach
gives us at least a rough cue as to what might be expected by any
general principle of interpretation (_189_).

Using age 7 as satisfactory in the first grade, 8 in the second, and so
on, we find that among 319 cities of all sizes, half of them had 2% or
more retarded four or more years in school position. This condition was
about the same for cities less than 25,000 as with the larger cities. On
the basis of school position for groups of children of all the school
ages it would, therefore, be safer to make a low estimate of the
frequency of mental deficiency on the basis of five or more years of
scholastic retardation in the groups and regard 4 years or more of
school retardation as a maximum estimate. Since most children leave
school at 14 it is generally best to regard all older as only 14 years
of age when estimating deficiency. I have not been able to check this by
school and test records on a group of children through all the grades.
Goddard's published records do not give the mental ages for those four
or more years retarded scholastically. Moreover, he only included those
in the sixth grade and below. For a group of young children this
estimate would undoubtedly be too low. The delinquent groups, however,
are all older. Most of them, if they lived in this country have gone to
school until they were at least 14 years of age. Wallin (_211_) and
Strong (_190_) also give records of school position to check the Binet

                                TABLE XV.


                              │          Percentages Retarded
                              │  4 or more grades  │  5 or more grades
 Cincinnati, Ohio—June 1907   │        8.8%        │        2.5%
 Cleveland, Ohio—1909-1910    │        3.0         │        0.9
 Des Moines, Iowa—1915        │        1.0         │        0.2
 Memphis, Tenn.—June 1908     │        6.6         │        1.5
 Minneapolis, Minn.—June 1915 │        1.3         │        0.5
 Pittsburgh, Pa.—1913         │        4.7         │        1.1
 Springfield, Mass.—Sept. 1907│        1.2         │        0.1
 Reading, Pa.—1906-1909       │        2.2         │        0.4

  The distributions for Cincinnati, Memphis and Springfield are taken
  from Ayres' Laggards in Our Schools. That for Minneapolis is from
  unpublished data. That for Reading is from Snyder's Retardation in
  Reading Public Schools. The others are from Superintendents'

By considering only pupils in the public schools who are 12 and 13 years
of age, the last years in which practically all are in school, we can
get a check upon this method of estimating for delinquent groups. I have
compared the age-grade distributions for those of these ages in eight
cities showing the percentages retarded 4 or more and 5 or more years.
They are given in Table XV. These records indicate that at least five or
more years retardation below a standard of age 7 in the first grade for
all who are 12 years of age or over might be taken for a low estimate of
the frequency of deficiency, and four or more years retardation for a
maximum estimate. Except under special circumstances those who are older
than 14 years should be considered as if the highest grade attained was
at 14 years of age. These borderlines of school retardation for the
purpose of estimating the frequency of deficiency check fairly well with
estimates for the Minneapolis and other groups of delinquents which have
been tested by the Binet scale, as we shall note later in this chapter.

In order that the school test of mental deficiency should be as good as
the Binet system it would have to provide a standard of school progress
relative to length of attendance instead of school position relative to
age. If one could say that a child was not above the lowest 0.5% of the
children of his age in the _progress_ which he had made in school
relative to the time actually spent in school, one would then have an
excellent standard for judging feeble-mindedness for any child who had
been in school for some years. It would be better if an uncertain region
were also defined. By the time that a child's ability has been passed
upon for four or five years and by different teachers, even from the
point of view of the needs of school work, one has a criterion for
mental ability in a particular community applied under long observation,
which no system of brief tests can hope to equal for some time to come.
Such a standard, however, is unfortunately not available since we have
too little information about school progress relative to attendance.
Even if it were available, psychological tests would still be an
important check upon the school judgment on account of the excessive
value put upon mere memorizing in school and on account of the emotional
repulsion to the school developed by some children of ability. Mental
tests would be necessary, moreover, for the younger ages.


Even if no more is known than a person's grade in school at any age over
eleven it is an important cue as to his mentality. Here our problem is
not estimating deficiency among groups but the discovery of deficient
individuals. We wish to find the highest grade in school in which we are
at all likely to find children under present conditions who test in the
lowest 1.5% for their ages. Our records on 653 15-year-olds indicate
that a pupil of this age who tests doubtful is very rarely retarded less
than 3 years in school. It occurred only twice when tested ability was
judged by the 1911 tests, four times judged by the 1908 scale. None of
the 15-year-olds who tested presumably deficient were retarded less than
three years. In Minneapolis, as in many cities, the custom prevails of
promoting, regardless of passable work, after two years have been spent
in a grade.

We suggest, therefore, to be perfectly safe, it is well for every child
in court to be examined who is two years retarded in school below the
standard age of 7 in the first grade and is not able to carry work above
the seventh grade. This will include a considerable number of children
at the lower border of those presumably passable.

Binet used this standard of two years retardation in recommending
examination for children 9 years of age or over (3 years below age 6 in
the first grade) (_77_, p. 44). He adopted it from Belgium. It is also
quite commonly followed in this country. The New Jersey law provides for
special classes in any school district where there are ten or more
children four or more years behind grade. This probably means behind the
theoretical position of age 6 in the first grade, one year worse
retarded than we suggest examining. Goddard says in one place that “a
child who has been in school regularly and is two or three years behind
his grade is so suspicious that it is almost certain that he is
feeble-minded” (_116_). But later he is much more conservative and says,
“The child who is fourteen years old and cannot pass an examination in
fourth grade work is almost surely feeble-minded” (_34_). As judged by
Strayer's tables the suggestion that examination is desirable for those
two years behind a standard of age 7 in the first grade would tend to
bring in for examination about 18% of the school boys in half of the
cities of 25,000 population and over. This would not be too severe a
burden for courts which would be interested only in that portion of
these retardates who were brought into court.

This school test may be made of decidedly practical use by those working
in juvenile courts where most of the cases are with children over this
age. It can be applied in a very simple manner by subtracting 8 from the
child's age and only passing without testing those who are in a grade in
school higher than the number remaining. For example, if the child is 13
years of age, subtracting 8 gives 5. Now, if the child is in the fifth
grade or lower, or entered such a grade at the time he was of this age,
one should investigate the question of feeble-mindedness. Unless more
than one year of the retardation is explained by the person's absence
from school since he was six years of age, he should always be turned
over to an expert for examination. This retardation of two years in
school attainment below the standard of seven in the first grade may
indicate feeble-mindedness if the child has been attending school
constantly, although the chances are perhaps 6 to 1 that it does not. It
is very desirable that we should have more adequate data on this point.
A cautious court, however, would inquire into the mental ability of any
child—at least two years retarded in school, _i. e._, any child the
number of whose school grade is not higher than the remainder after
subtracting 8 from his life-age at the time that he entered his last
grade or who is not actually carrying the school work of an advanced
grade. This latter caution we must now consider.


The school test can give us still another practical cue as to
feeble-mindedness in examining children. Ability to carry successfully
school work of some grade certainly could be used as a systematic
criterion of passable intellectual ability. What school grade indicates
this is not at present possible to determine except as a rough practical
check. With the great irregularity in school grading at present known to
exist, it certainly would not be possible to say that fifth grade work
indicates a passable intellect, although some of the oldest local
schools for deficients, like those in Mannheim, do not pretend to carry
children above the fourth grade work. Speaking of the school success of
the intellectually deficient, Binet said: “One may draw the conclusion,
which is of practical value, that one need not seek children of this
group in the senior divisions of the primary schools” (_77_, p. 44).
This would correspond to the sixth and seventh grades in this country.
Tredgold gives a careful description of the highest work in a London
special day-school for the highest grades of deficients. It shows that
even fifth grade work would be beyond what is actually taught the
children in this school. He says:

  “The work done by this class consists of reading and writing,
  equivalent to normal Standard II; compound addition and subtraction
  up to 1000, and simple multiplication and division. Excluding a few
  children—who, in my opinion, are not really defective—it may be said
  that the scholastic acquirements of none of these children come up
  to the Standard II. In occupations and manual work they are
  decidedly better, and a considerable portion of the children of this
  class can cut out and make simple artificial flowers, knit rugs and
  weave baskets, with a really very creditable amount of dexterity,
  which redounds in no small measure to the patient, persevering and
  systematic care of their teacher” (_14_, p. 173).

Some of our group with doubtful intellects do better than this. When
considering the borderlines with the Binet tests we decided that a child
was presumably passable if he scored a test-age of XI. This score would
not be made by 11-year-olds as a group, but could probably be attained
by 12-year-olds. We may then ask what is the corresponding school
position attained by 12-year-olds who have been continuously in school.
At the same time we must ask whether the lowest 1.5% of the children of
any single age can attain this school grade since it should be high
enough to exclude the deficients, no matter how long they have attended
school. We happen to have this information for a random group of
Minneapolis elementary school pupils on the basis of census of school
progress per years of schooling. Considering only the children who had
been in school since they were six years of age, we found that 82% of
186 12-year-olds and 92% of 174 13-year-olds had reached the seventh
grade, and that the lowest 1.5% of neither age nor of any of the older
ages could apparently carry the work of this grade no matter how long
they had remained in school. Our records included older pupils who were
in their eleventh year of attendance on the elementary schools.

Another indication that reaching the seventh grade is presumptive
evidence of passable intellects is found in the fact that none of our
group of 653 15-year-olds testing presumably deficient with the Binet
scale and only four of the six who tested doubtful intellectually had
reached the seventh grade. On the other hand those that think that a
15-year-old testing XI is deficient will be interested to find that 42
out of 51 who tested XI with the 1908 scale were in the seventh grade or
above. We are convinced, therefore, that it is a conservative position
to take that either passing the Binet tests XI in the 1908 series or
ability to pass successfully the seventh grade in school is good
evidence of a passable intellect. The rule, of course, does not apply to
those who are passed along to the seventh grade because of their size or
age regardless of ability to carry the work.


Let us see what the rough preliminary estimates on the basis of school
retardation would indicate for the Minneapolis delinquents. We may
disregard the upper limit of 14 years since compulsory attendance in
Minnesota for backward pupils continues until age 16. For the limits of
five and four years of retardation in school below the standard of 7
years in the first grade we would have estimates of 2.6% to 6% of
deficiency among the ordinary cases of delinquent boys and 14.7% to
23.1% among the ordinary delinquent girls. Among the recidivist group of
boy offenders 3% to 11% would be below these borderlines. Among the Glen
Lake School group 12% are four years or more and 4% five years or more
retarded. This last is to be compared with our judgment on the basis of
individual examinations with the Binet scale in which we concluded that
2% were presumably deficient and 5% doubtful as to deficiency. The
estimates on the basis of school retardation are somewhat too large.
This would certainly be true for older delinquents. In as much as the
laws for compulsory school attendance usually do not enforce attendance
after 14 years of age, it would probably be better generally to treat
all over 14 years of age as if they were of this age at the time of
leaving school. This limiting age of 14 checks more closely with the
mental examination records reported by Williams (_149_) and Ordahl
(_41_) for groups of delinquents in the California state schools.

With her unselected group of 88 women at the Bedford reformatory,
Weidensall found that 39% had not completed the fifth B grade (_60_, p.
23). This is not far from the estimate of presumable deficiency among
such inmates on our borderline with the Binet scale. Considering the
actual years of school retardation relative to years of attendance, so
far as she was able to discover, and adding the 8 who never attended
school, we have 20% five or more years retarded in school and 28% four
or more years retarded (_60_, p. 251). She says further regarding the
bi-modal distribution of ability which she found among her group:

  “The division which alone served to separate the better from the
  poorer subjects was that of the grade completed upon leaving school.
  Those who had accomplished the completion of at least 5B grade
  formed a curve which paralleled very closely that of the Cincinnati
  girl of fifteen, while those who had not succeeded in passing 5B
  comprised the majority of those who collected at the poorer mode of
  the Bedford 88 curves. Throughout, the grade completed has proved to
  be more often a measure of our subjects' ability to progress in
  school, less often a measure of their opportunity to attend school.”

The administrative officers of institutions may make rough estimates of
the frequency of serious deficiency among their charges by regarding all
over 14 as if they were 14 years of age or under, disregarding those
under 12 years of age, tabulating the highest school positions reached,
and finding the frequency of those four or more and five or more grades
retarded below a standard of age 7 for the first grade. It would be well
for each court also thus to make an estimate of the size of the problem
of deficiency in its jurisdiction. According to the second suggestion
which we have made, the Minneapolis Juvenile Court, for example, should
plan to examine for mental deficiency all those two or more years
retarded in school or about 20% of the boys found delinquent and nearly
half of the girls. The prospect would be that the number sifted out as
having feeble intellects will be less than 10% of the ordinary run of

Let us study a little further into the detention home cases tested by
the Binet scale and see what additional light their school position
throws upon the question whether or not they are defective delinquents.
Four years retardation in school position would have called attention to
both of our sure cases of feeble-mindedness. On the other hand, it would
have brought in for examination only 4 out of the 7 doubtful cases.
Three years of school retardation would have sifted out all but one. Two
years school retardation, the rule suggested above, would have detected
all those who tested doubtful. It would have required 56 examinations in
this group to have found the eight cases suspicious under our test
criteria. We also find that, among the random 15-year-olds not
delinquent, examining all those 3 years retarded would have discovered
all that tested even doubtful intellectually.

Applying the rule that ability to carry seventh grade work is a good
indication of a passable intellect, we find that none of our Glen Lake
delinquents testing either presumably deficient or doubtful had reached
the seventh grade. On the other hand, if one were disposed to object to
saying that a person who passes Binet tests XI (1908) has a passable
intellect, one finds in reply that 16 out of the 22 Glen Lake delinquent
cases testing XI and three or more years retarded intellectually, _i.
e._, presumably passable, were carrying seventh grade work or better.

In examining individuals the importance of checking each of these tests
with the other seems perfectly clear. If a boy fails in the Binet tests
and shows better school ability one should certainly be cautious in his
diagnosis. On the other hand a boy who is seriously behind in school may
be found by the Binet scale to have a better intellect, so that the
inquiry must be further extended to determine the cause of his school
retardation. Retardation in school is generally not as fundamental a
symptom of deficiency as retardation in the tests because of the
numerous other causes of delay in school.

After allowance for the external causes of backwardness in school one
finds that the test of progress in school and the Binet examination not
rarely reach two different sides of the nature of unusual children found
in juvenile court. Working with these exceptional children, Dr. Kramer
observed that school performances were often notably different from
ability in the tests. After checking the two tests against each other in
examining 59 cases sent to him from the Society for the Care of
Delinquent and Dependent Children in Breslau and 59 children at the
psychiatric clinic in Berlin, he says regarding the result of this

  “For the valuation of the Binet method, it shows us that the first
  objection which occurs to one, that the method tests only school
  knowledge, is not correct. On the contrary it was found that we had
  to do in high degree with that which was independent of what the
  child had learned in school and with real abilities which the normal
  child is accustomed to acquire by a certain age uninfluenced by
  training and instruction.”

He emphasizes, however, that to answer practical questions regarding the
training of a child, “we must not only examine into the understanding
but the total personality must be taken into consideration” (_184_, p.


The comparison of the Binet and school tests for our group of serious
delinquents suggests another important comparison. Many delinquents are
found to be apparently wrongly placed in school relative to their
intellectual development. They form a group for which not isolation but
training is needed, a group notably larger than that which should be
sent to institutions for the feeble-minded. This bad adjustment of
juvenile delinquents to their school work is not the same problem as
backwardness in school. It means attendance in school classes unsuited
to the child's mental ability. In a paper before the Minnesota Annual
Conference of Charities and Corrections in 1910, I briefly forecasted
this problem (_152_). It is now clearly indicated by the records of the
group of delinquents at the Glen Lake Farm Training School. This
comparison is made in Table XVI.

                               TABLE XVI.

                        INTELLECTUAL DEVELOPMENT

   School position   │  Alike[32]  │          Better           │Total
        worse        │             │                           │
 3 yr. │2 yr. │1 yr. │      │      │1 yr. │2 yr. │3 yr. │4 yr. │
   1   │  8   │  21  │  21  │  29  │  16  │  4   │  2   │  2   │ 104

In order to be thoroughly conservative in estimating this problem of
maladjustment to school work, let us not only allow for two mental ages
to be satisfactory for each grade, as indicated in the table, but in
addition omit all cases which might be credited with an intellectual
development above XII. This eliminates the objection to considering
higher age tests, for nobody questions that tests XII or above indicate
at least a 12-year-old intellect. After these extremely liberal
allowances we still find 54 of the 104 boys in the detention home
testing less than XIII who were in school grades the work of which was
presumably not suited to their intellectual level. Seventeen of the boys
(16%) were at least two years out of adjustment to their school work. If
we disregard those who were trying to carry work too difficult for their
capacity because placed a year or more ahead of their ability, we find
30 out of adjustment because at least one grade behind the class suited
to their intellects. Over a quarter of our detention-home group was thus
placed in school a year or more below grades attended by the pupils of
corresponding intellectual development. It may be said that some of
those behind their proper intellectual position in school may have been
kept back because of instability, laziness, or other volitional
characteristics which might fail to show in tests of intellectual
performance. This is probably rare, and, when found, it often means
merely that the pupil requires more attention to secure results.

That our delinquents are not unique in their maladjustment to school as
judged by their tested abilities, is indicated by the report of Ordahl
on the school position of the special group of 341 delinquents in the
state school at St. Charles, California. The median of their school
positions, counting seven years as satisfactory for the first grade,
fell a grade and a half below that which their tested mental development
seemed to justify. He notes that “mentality is not alone responsible”
for their low grades in school. Moreover, he believes that it shows the
necessity for a more objective pedagogical method in dealing with them
(_41_, p. 81).

Only a prolonged trial of special instruction for those presumably
behind their proper grade would finally determine how large is this evil
of maladjustment. Such an experiment could be satisfactorily carried out
only with the co-operation of the board of education. It would mean the
employment for some years of expert teachers to train those delinquents
found behind their intellectual level in school. Until that time we
shall have to take the estimate from psychological tests which indicated
that, in our group of serious juvenile delinquents, presumably 29% of
those compared had been held back by the school machinery. Since the
retardation of these pupils may be attributed to a late start in school
life or prolonged absence, the inadequacy of the schools so far as these
pupils are concerned may be supposed to lie in their failure to promote
pupils quickly up to the school position of their equals. On account of
the expense of special teachers such pupils presumably could not be
given a chance to make up the school subjects which they had missed and
could not be advanced to the grades requiring this knowledge. Whenever
this is the case or under any circumstances which keep the pupil behind
the school class of his intellectual equals, we have a fundamental cause
of distaste for school work. No wonder that such pupils dislike school,
become disgruntled and stubborn, run away and rebel at the treatment
they receive under the traditional school system. One can hardly blame a
self-respecting boy, forced to remain behind his peers, for breaking
away from the lock step, playing truant and seeking his education in the

The trouble is not with the school authorities alone. They are doing
about as well as can be expected with the funds which the people have
been willing to provide. The public must be educated up to the
recognition of the fact that every child in the school should be allowed
to progress as rapidly as his abilities permit. The public schools of
Mannheim, Germany, are the great illustration of what can be done to
bring the school instruction close to the varying degrees of capacity
among the pupils. In the Mannheim schools children may carry from four
to eight years of the regular curriculum in eight years, and the
brighter pupils may also take additional subjects. The Industrial School
in Cleveland has demonstrated that some 14-year-old boys two years
backward in school may, with special help, be successfully prepared for
high school with about as much likelihood that they will continue the
high school course as the ordinary boys (_107_).

It is self-evident that a boy with ability to carry a higher grade of
work cannot ordinarily be allowed to skip one or two classes without
special instruction and be expected to succeed with studies which
require preliminaries that he has had no opportunity to learn. The
necessary knowledge and sufficient skill in particular habits of thought
needed could probably be acquired in a brief time under the right sort
of special instruction. It is not sufficient that special classes for
pupils mentally backward should be provided in the schools. They will
not take care of this problem, which has to do mainly with pupils
intellectually capable of carrying the work of a higher grade than that
in which they are placed. These children can now be found by means of
mental tests and they should be assisted in making up the intermediate
work by collecting them into redemption groups, so to speak, where they
can have individual instruction. In the public schools of Faribault,
Minnesota, the plan of thus picking out older minds in a class and
promoting them one or two grades with very little extra instruction has
been successfully tried in an experimental way.

If all of the children in a school system who are thus seriously out of
intellectual adjustment cannot be cared for, it is plain that the
children in danger of delinquency might well receive the first
attention, since the lack of adjustment with these may cause the most
serious social consequences. That the problem is more acute among the
serious offenders in juvenile court than among school children generally
is indicated by a comparison with Goddard's figures for school children
generally in a typical community tested with the same scale. If we
select from his tables only that group of mental ages which could
actually be in a class ahead or behind their mental development, we find
that only 20% of this group would be outside the standard of 6 and 7
years in the first grade, etc., as compared with 52% of our detention
home group on the same basis. On the other hand Terman's records with
the Stanford scale (_193_) indicate 44% of ordinary children similarly
maladjusted to school. This condition should probably be regarded,
therefore, as a supplementary stimulus for delinquency rather than a
fundamental cause comparable with mental retardation.

While this lack of adjustment is undoubtedly the most pressing
_training_ problem connected with juvenile delinquency, we must not
expect that when it is solved we shall have eliminated the problem of
mental backwardness of delinquents as a class. The most that we could
expect from perfect adjustment of the school work to mental ability
would be that the average amount of school retardation for the group
would be materially reduced. How much retardation in school relative to
the life-ages would still remain, cannot be determined on account of the
uncertainty of the tests for older ages and the factor of volition. For
the mentally deficient pupils still remaining behind the regular pupils
it is necessary to provide other special classes. In these classes or
schools the feeble-minded children would remain for their entire school

That the correction of the lack of adjustment is a much more agreeable
and hopeful task than the care for deficients is shown by the facts
regarding the detention home group in Table IX. There is at least the
possibility that 10 of the school laggards in this group of serious
delinquents might be brought up to a satisfactory grade. Discount this
prospect as you may, it is still to be compared with the fact that no
actually feeble-minded boy can ever, by special instruction, be brought
up to a satisfactory school grade. Moreover, we might expect that 30 of
the 84 laggards might, by special help, catch up one or more grades.

That the correction of lack of school adjustment is a bigger problem in
connection with juvenile delinquency than the detection and isolation of
the mentally unfit can only be said in relation to the numbers affected.
Taking the lowest estimate of those in the detention home group out of
adjustment with their school environment it was at least 30, while only
9 of that group fell below the borderline of passable intellects and
only 2 were surely feeble-minded. If one guessed as we have on the basis
of school position that a maximum 6% of the ordinary juvenile
delinquents in Minneapolis might be feeble-minded, who would venture to
guess that ill-adjustment of school to mental ability affects so small a
proportion? On the other hand one feeble-minded person, through the
transmission of his deficiency, may, perhaps, do more damage to society
than many intelligent delinquents. Who shall say? Certainly both the
isolation of the feeble-minded and the adjustment of school training are
vitally important problems in the care of juvenile delinquents today.
Nobody can say that one is more important than the other except from a
special point of view. From the eugenics standpoint feeble-mindedness is
more important; from the point of view of the numbers affected and the
skill required for training the child, there can be little question but
that the correction of bad adjustment to school environment is the
bigger problem. When one considers how much of the child's time is spent
out of school, at home, with playfellows, or at work we cannot be sure
that other external influences might not ultimately be found to be more
important in connection with juvenile delinquency than either the school
life or mental incapacity. The further consideration of the causes of
delinquency we shall now make the subject of a broader inquiry.


Footnote 32:

  Mental ages VI and VII regarded as satisfactory for the first grade,


In a preceding chapter we have shown the frequency of tested deficiency
among various types of delinquents. We may now further consider the
significance of this association of delinquency with deficiency. The
best plan for discovering its meaning is provided by the technical
method of correlation. The data in the published reports of the score or
more of investigations which I have reported is wholly inadequate for
following out this method. We must, therefore, for the present content
ourselves with noting what has been discovered by the better analysis of
similar data which was supplemented by the necessary information as to
the distribution of the different types of crime in the corresponding
general populations. To this we can add certain correlations in
connection with the small Minneapolis group of tested juvenile

We are indeed fortunate to have the fundamental work of Dr. Charles
Goring on “The English Convict,” from which to formulate a point of view
regarding the relation of deficiency and delinquency. This work
represents ten years labor in making observations, collecting,
tabulating, and statistically evaluating data on 3000 convicted men, who
were found in the English convict prisons where they had been sent after
conviction in the higher courts because guilty of grave or repeated
offenses. It was carried out with the co-operation of a corps of workers
who had the help of Professor Karl Pearson and his assistants at the
Biometric Laboratory of the University of London, in the statistical
reduction of the almost overwhelming mass of data. By the large use of
partial correlation the _relative_ influence of various factors upon
criminality was investigated as it never had been before. It is, of
course, not possible to reproduce here the conclusions of this
monumental work which should be made more widely available in the
libraries of this country. We shall, however, select certain conclusions
which bear most directly upon our problem and which rest upon well
established statistical deductions, and compare them with a few other
studies which have contributed interesting side lights upon the causes
of delinquency.


“Every feeble-minded person is a potential criminal,” says Goddard in
his work on _Feeble-Mindedness_ (_112_, 514), and this sentiment finds
an echo in the emotions of many social workers. On the other hand we
have the careful work of Bronner in which she compares by their test
records a group of delinquent women with groups selected from night
classes and the servant class who had never been known to be immoral. On
the average she finds that the delinquents do not test below her servant
group. She says:

“Thus, though our delinquents are not as capable as their sisters, many
of them from congested districts, who in other ways are proving
themselves ambitious [the group from night classes,] yet they are no
less equipped intellectually than others who are earning a livelihood
and caring for themselves without coming in conflict with the law in the
least. Whatever their mental status might be, measured by other means,
the fact remains that there is no _necessary_ correlation between their
immoral or criminal tendencies and their intellectual ability and that
others, no more endowed than they, are fighting life's battles without
manifesting the same immoral or criminal tendencies” (_112_, p. 43).

What portion of these moral household servants of equal ability with the
delinquents may later fall under temptation, we, of course, cannot say.
Neither can we say that any of the delinquents would test deficient,
since we do not know the border lines of deficiency with the tests which
were used. The conclusion, however, is clear that, if corresponding
grades of intellect may be delinquent or not at maturity, we must be
cautious in assuming that the lowest grades of intellects would all
become delinquent if not under supervision.

What chances we are running by allowing feeble-minded individuals to be
abroad might be determined if we could find out the probability of
tested deficients becoming delinquent. This question cannot be answered
by showing for a single year or a period of years that crimes are
relatively more common among the defective classes, although such
figures give some impression of the danger of deficiency to the

Kinberg, for example, calculates that in Sweden during the years
1901-1907 murder was relatively 200 times as common as among those not
in institutions, but lacking criminal responsibility through insanity or
deficiency, as among those who were responsible, arson was 72.5 as
common, manslaughter 12.63 times, other injuries to property than arson
6.55, rape 6.1 times, infanticide 4.59 times, larceny 0.99 times, and
fraud 0.26 times (_132_). The data were based upon the reports of the
Royal College of Health which makes the diagnosis as to criminal
responsibility that is required for all cases in which this question
arises. Such examinations, it is estimated, miss at least 15% of the
deficient criminals.

Goring gives a table which shows what crimes are most likely to be
committed by deficients. He found that 10% of the convicts in England
and Wales were definitely treated in prison as deficient, and he
estimated that 0.5% of the non-criminal population were equally
deficient. His table is based upon the tabulation of 8,290 crimes past
and present of 948 English convicts (Fig. XXXIX, p. 258). It is given

                              TABLE XVII.

            CONVICTED OF VARIOUS OFFENSES. (_948 Convicts_)

 Firing of stack                                                   52.9%

 Wilful damage, including maiming of animals                        22.2

 Arson                                                              16.7

 Rape (child)                                                       15.8

 Robbery with violence                                              15.6

 Unnatural (sexual) offenses                                        14.3

 Blackmail                                                          14.3

 Fraud                                                              12.8

 Stealing (and poaching)                                            11.2

 Burglary                                                           10.0

 Murder and murderous intent                                         9.5

 Rape (adult)                                                        6.7

 Receiving                                                           5.1

 Manslaughter                                                        5.0

 Coining                                                             3.3

 Wounding, intent to wound, striking superior officer                2.9

 Embezzlement, forgery, fraudulence as trustee, bigamy, performing   0.0
   illegal surgical operation

 General population                                                  0.5

Another table from Goring shows which groups of crime are most likely to
be committed by the deficients compared with the frequency of that type
of crime in the general population. It is reproduced in part below.

                              TABLE XVIII.

                           MENTALLY DEFICIENT

 Nature of crimes │  Total  │Mentally │ Percentages of │ Percentages of
                  │criminals│defective│     mental     │    general
                  │         │         │defectives among│   population
                  │         │         │those committing│ committing the
                  │         │         │ various crimes │several offenses
 Malicious damage │       55│       22│           40.00│           0.406
   to property    │         │         │                │
 Stealing and     │      442│       45│           10.18│           4.180
   burglary       │         │         │                │
 Sexual offences  │      101│       13│           12.87│           0.199
 Violence to the  │      183│       11│            6.01│           1.606
   person         │         │         │                │
 Forgery, coining │      167│        4│            2.40│           0.722
   and fraud      │         │         │                │
       Total      │      948│       95│           10.00│           7.203

Some very striking instances of recidivism on the part of the
feeble-minded were summarized by Dr. Smalley in his evidence before the
Royal Commission (_83_). He said:

  “Against 130 out of 333 weak-minded prisoners who were unfit for
  ordinary penal discipline by reason of mental deficiency, no
  previous conviction had been recorded; but for this absence of
  record their nomadic habits might in part account. Against fifty-six
  1 conviction had been recorded, against twenty-eight 2; the
  remainder varied from 4 to 105 convictions. About half had been
  convicted from 5 to 10 times.... Dr. Hamblin Smith, Medical Officer
  of Stafford Prison, as the result of a special inquiry into 100
  mentally defective prisoners, found that 100 had a combined record
  of 1,104 convictions, or an average of 11 per prisoner, and this
  number was regarded as being below the actual truth. Ten of the
  prisoners had over 30 convictions. Dr. W. R. Dawson found that in
  the two prisons in Dublin 12.21 per cent. of the inmates were
  defectives. The average number of previous convictions for the
  females was 44.13. Many of them ran into hundreds, and one was in
  prison for the two-hundred and thirty-sixth time, and she was only
  twenty-nine years old.”

So far as I can discover nobody has directly attacked the specific
problem, what percentage of individuals of a given degree of deficiency
who are not under supervision, become legally delinquent at some time in
their lives. A slight contribution to the empirical study of the problem
is made in the reports of the follow-up work in connection with pupils
formerly in special classes in the public schools which I reviewed in
Chap. IV, f. We have also a telling report by Bullard of the New York
Prison Association published by Moore in 1911 (_156_). It follows the
records of 85 feeble-minded boys and men 16-29 years of age, paroled
from the Elmira State Reformatory in 1904. The whereabouts of 3 were
unknown and 2 died. Of the remaining eighty, 31 were arrested again and
6 others violated their parole. One was arrested 19 times in this short

The best approach to this problem of measuring the potential delinquency
among deficients is afforded by Goring's four-fold table for calculating
the correlation between deficiency and criminality in the male
population of England and Wales (_20_, p. 259). By means of the annual
data on first convictions of crime at different ages and the probable
length of life among criminals and in the general population he has been
able to predict a potential criminality on the part of 7.2% of the
general male population. In other words, the best estimate seems to be
that about 7 in every hundred males in England and Wales will be
convicted of crime at some time in their lives. About 10% of the
convicts in England for a series of years have been isolated in prison
treatment because of deficiency. If we now also assume with him that
0.46% of the non-criminal population is mentally deficient, we arrive at
the table which enables us to determine, on these assumptions, that it
is most likely that 63% of the deficients will be convicted of crime at
some time in their lives. If instead of taking this estimate of 10% of
the criminals being deficient we had taken 20%, then the probability of
a deficient individual being convicted of crime would rise to .77.

On the basis of our summary of tested delinquents in the last chapter it
seems extremely conservative to suppose that 10% of the manifest and
potential criminals are as deficient mentally as the lowest 1.5% of the
general population. Even with this assumption we find that the chances
would be 48 out of a hundred that a person of this degree of deficiency
would be convicted of crime.

These estimates, I believe, afford a telling argument for the indefinite
isolation of at least those who are in the lowest 0.5% mentally on the
ground of their potential criminality, independently of any question of
the danger to society from the hereditary transmission of the diathesis
of deficient delinquency.

We have heard much in recent years of the particular danger of allowing
the better grade of feeble-minded, especially the morons, to be abroad
in the community. Time and again it is asserted that it is this class of
deficients which is most likely to become delinquent. There is a
widespread confusion here between the statement that criminals in
absolute numbers are drawn more frequently from the moron class and the
statement that morons are relatively more likely than imbeciles or
idiots to become delinquent. To the first alternative there would be no
objection since morons are much more frequent than the lower grades of
deficiency. On the other hand if morons are relatively more likely to be
delinquent than imbeciles, then we should expect those just above the
morons in ability to be more likely than morons to be delinquent. The
technical answer to the problem whether the lower grades of deficiency
are more likely to become delinquent could be best reached by
discovering the correlation of delinquency with the different grades of

Goring's data throw some light on this question since he has found the
correlation between grades of intelligence and the degree of recidivism
and also between intelligence and the frequency of bad reports in the
penal institutions where the convicts were held. In both cases the
tendency is clear for the weak-minded and imbecile to be more frequently
convicted and to be reported more frequently for bad conduct than for
the higher grades of intelligence which he classifies as unintelligent,
fairly intelligent and intelligent. The correlation coefficient with
frequency of convictions relative to time out of prison is -.16 and with
frequency of bad reports is -.33. The correlation ratios are slightly
higher in both cases. On the other hand the more intelligent are likely
to be given longer sentences, the correlation being +.10.[33] It might
be contended that his distinction between the lowest grades of
intelligence is not objective and not very clear; but that the general
tendency of the regression lines would be reversed at the lower extreme
seems very improbable. In other words there is some reason to suppose
that, relative to their numbers, the idiots and imbeciles would be more
likely to be delinquent than the more intelligent feeble-minded provided
none was confined in an institution. No idiot and few, if any, imbeciles
could survive honestly in any environment without assistance.

How closely the degrees of immorality are associated with the degrees of
deficiency remains one of the most important problems to be answered
authoritatively by the correlation of these traits when properly
measured. That the greater degrees of immorality and of deficiency are
on the whole associated and not opposed we have good reason to believe,
but there are undoubtedly examples in which the degree of immorality or
delinquency is out of proportion to the degree of deficiency. The fact
that certain instances are found of moral imbeciles without
corresponding intellectual deficiency, which has been noted by Stern
(_188_, p. 75) and by Anton (_67_), does not of course determine the
direction of the tendencies. We must base our deductions as to the
danger of delinquency among lower and higher grades of deficients on our
knowledge of the general tendencies. Are morons, relative to their
numbers, more dangerous to the community than lower grade deficients? We
must not make the absurd deduction that because morons are most numerous
they are most likely to be delinquent and should therefore be most
carefully isolated or supervised.


Modern statistical methods afford the ultimate quantitative tool for
determining the cause of delinquency, whether or not we also require
that the data should be assembled under experimentally controlled
conditions. The rapid strides which have been made in answering this
fundamental question of criminology may be judged by noting the
treatment of it in such a work as Goring's compared with the
impressionistic literary style which has prevailed. Illustrations of
particular cases, opinions subconsciously formulated by experts from
wide experience in dealing with delinquents, even the votes of the
majority of leaders in the field, give way before the acid test of
measurement of tendencies in human traits just as poorer methods
succumbed in the Middle Ages in the realm of the physical sciences.
Quantitative determinations can no longer be brushed aside with a smile
on the supposition that statisticians are the biggest liars. They must
be answered by better data or more refined methods. The form of the
discussion of social questions has changed. Correlation is a powerful
new weapon for attacking these problems which promises to go far beyond
the range of earlier blundering methods.

While partial correlation affords an ideal approach to answering the
question of causation, it has been used only to a very limited extent.
The necessary data for comparing the closeness of relationship of
various suggested causes of delinquency are not available and too few
who are interested in social problems have appreciated the significance
of the method. We should, therefore, lay especial emphasis on the
measurement of the correlation of deficiency and criminality by Goring.
He laboriously assembled the only data which are sufficiently extensive
to allow much reliance to be placed upon their statistical reduction. In
his use of correlation, moreover, he acted under advice from the main
center for this work at the Galton Laboratory in London.

If those who were “mentally defective” under Goring's designation were
always convicted of crime and none of those who were not defective were
ever convicted of crime, the measure of the relationship between
criminality and deficiency would be expressed by a correlation
coefficient of +1.00. If there were no relationship whatever between
deficiency and criminality the coefficient would be 0.00. If the
deficients were never convicted of crime and the non-deficients were
always criminal the coefficient would be -1.00. Intermediate degrees in
the relationship of these tendencies would then be represented by
decimals which would be either positive or negative, depending upon
whether the traits were associated together or were opposed. The
coefficient which he found for the male population was +.6553, which was
much higher than that for any other constitutional or environmental
factor which he measured.

In calculating this correlation Goring regarded 10% of the criminal male
population as defective. He found that this was in agreement with the
common tendency in English convict prisons to class officially about
this portion of the criminals as defectives and needing care. He also
assumed that 0.46% of the non-criminal male population in England and
Wales was defective, the proportion suggested by the report of the Royal
Commission on Feeble-mindedness. By a careful computation he calculated
that 7.2% of the males either have been or will be convicted of crime
before they die. He then constructed the four-fold table on the basis of
these estimates as applied to the 948 convicts whom he examined as to
their mental condition. The coefficient was then calculated by Pearson's
method for a four-fold table. This method assumes that the mental
ability and the tendency to criminality are distributed normally in the
population and that the difference in numbers between the criminal and
the non-criminal, deficient and non-deficient are not too great. In case
the percentage of defectives among the criminals were taken as 20%
instead of 10% the correlation would be increased to .79.

Using the same four-fold method we may calculate the correlation between
deficiency and juvenile delinquency among Minneapolis boys. It is
necessary to make a good estimate of the proportion of boys who annually
become delinquent in Minneapolis for the first time, and of the
proportion of these boys who are correspondingly deficient. Fortunately
these comparisons can be made fairly accurately on the basis of the
reports for the year 1915 and of our tests of juvenile delinquents. We
may use a minimum and a maximum estimate of deficiency among the
delinquents corresponding to those that tested below borderlines which
represented the lowest 0.5% and the lowest 1.5% of the population of
corresponding ages. We need to assume that the frequency of tested
deficiency among the boys found delinquent would correspond within these
limits to the frequency among the Glen Lake group. The indices for the
amount of school retardation in these two groups (Table XIV) indicate
that this is a liberal estimate. We must also assume that the proportion
of juvenile delinquents for the year 1915 may be regarded as typical for
a series of years. The number of new cases of boys in juvenile court in
1915 was within 18 of the median number for the last four years. The
result of these estimates is Table XIX for the minimum estimate of
deficiency. A similar table for the maximum estimate of deficiency would
be the same, except that the proportion of all boys of these ages who
were deficient would be 1.5%, and of the delinquent group, 7.3%.

The computation of the correlations by Pearson's tetrachoric _r_ shows
the relationship between juvenile delinquency and deficiency among boys
to be .16, P. E. .07, on the minimum estimate of deficiency. On the
maximum estimate the correlation is .29, P. E. .05. In order to make a
closer comparison between Goring's calculation and my own I have
recalculated the correlation for his group on the assumption that 0.5%
of the general male population were deficient and that 1.29% would be
convicted felons of the type among which he found 10% to be deficient.
This brings the minimum correlation for his figures to .59, P. E. .03.

                               TABLE XIX


                         BOYS 8-16 YEARS OF AGE

                  │  Non-Deficient  │    Deficient    │      Total
 Non-Delinquent   │           22,305│              109│           22,414
 Delinquent       │              268│                4│              272
       Total      │           22,573│              113│           22,686

  The total number of boys is taken from the census of school children
  for 1915-16 compiled by the attendance department of the Board of
  Education. It includes those in public, parochial and private
  schools and those not attending. The number of delinquent boys is
  taken from the report of the Juvenile Court of Hennepin County,
  Tables H and I. The number of repeaters and the proportion of
  delinquent cases dismissed at the hearing are subtracted from the
  total number of new cases.

The difference between a correlation of .29, the highest I found, and
.59, Goring's lowest result, indicates that conviction for felony in
Great Britain is more closely associated with deficiency than juvenile
delinquency is associated with deficiency in such communities as
Minneapolis. It is to be remembered, however, that Goring's calculation
gave the convicts a life-time in which to be convicted, while ours gave
the boys only 16 years. The relation of potential delinquency after 16
years of age to deficiency might be greater among Minneapolis males than
the corresponding relation we found among the boys; but the difference
in these correlations is more easily explained by supposing that the
type of serious delinquency represented by sentences to penal servitude,
in England at least, is more closely related to deficiency than are the
lighter forms of delinquency found among the youth of an American city.

The most significant fact demonstrated by the correlations between
juvenile delinquency and deficiency is that there is a positive
relationship which is significant in amount. With the maximum estimate
the correlation is nearly 6 times its error. This is the first time that
the relationship has actually been calculated in connection with any
group of juveniles. We can say that when a Minneapolis boy is below the
average in tested ability for his age, he is most likely to be .16 to
.29 of the same amount below the average in legal conduct, both
measurements being in corresponding units.

What then, is the significance of correlation in answering the problem
of causation? So far as the statistical method itself is concerned it
shows only a mathematical functional relation between the conditions
measured, not a physiological relationship. In other words a correlation
between deficiency and delinquency might be explained by both conditions
being related to some more fundamental factor which might be the causal
factor involved. One cannot reason from correlation to direct causal
connection. On the other hand, by correlation we may directly compare
the relation between any one trait and various factors. We can find out,
for example, whether the association of delinquency with deficiency is
closer than the association of delinquency with other factors which it
has been suggested are causes of delinquency. Goring's work allows us to
compare the correlation of the tendency to be convicted of crime with
deficiency and with many other constitutional and environmental factors
which have been measured, and thus our attention may at once be directed
to that factor which the present evidence indicates as most fundamental.
Unless the measurement of the various factors is shown to be seriously
faulty or incomplete the outcome should determine our point of view as
to the main cause of delinquency, until new evidence is forthcoming.
This is the problem of the next section.

                     C. THE CAUSES OF DELINQUENCY.

As we have noted above, the correlation of delinquency with various
factors should give us a scientific point of view as to the main causal
influence in criminality. Thanks to Dr. Goring this work has recently
been carried far. His findings mark a new and higher scientific level in
the study of criminology. No data are now available which modify his
position in any important regard. I shall, therefore, attempt to give
his evidence in the briefest possible manner, hoping that it may lead to
a closer reading of his basal investigation.

                      (a) CONSTITUTIONAL FACTORS.

First comparing a dozen factors in the individual's own constitution
which may be measured by the death rates, Goring found the tendency to
be convicted of crime was correlated most closely with alcoholism, .39;
sexual profligacy (syphilis and aneurism), .31; and epilepsy, .26; while
it was found to correlate with intelligence, .66. The closeness of the
relationship of defective physique to criminality was expressed by
coefficients of .18 and .19. Among the inner factors investigated were
many of Lombroso's characteristics of the so-called criminal physiognomy
of which so much use is made by phrenologists, such as asymmetries,
projection of the chin, complexion, form of the face and features, kind
of hair, tattooing, left-handedness, temperament, etc.

Following this analysis, we find that alcoholism, epilepsy, and probably
social profligacy are closely associated with intelligence as well. By
means of partial correlations he shows that when individuals of the same
degrees of intelligence are compared there is only slight additional
relation between alcoholism or epilepsy and criminality. The relations
to these other conditions are therefore accidental, depending upon the
fact that deficients are more likely to be alcoholic and epileptic, the
fundamental constitutional factor being intelligence. Among over forty
physical and mental factors, the only other condition which he found to
have significant relation to criminality is a generally defective
physique as shown by height and weight, neither of which is correlated
with intelligence.

Regarding the above inner factors he summarizes his conclusion as

“Our final conclusion is that English criminals are selected by a
physical condition, and a mental constitution which are independent of
each other—that the one significant physical association with
criminality is a generally defective physique; and that the one vital
mental constitutional factor in the etiology of crime is defective
intelligence” (_20_, p. 263.).

                         (b) EXTERNAL FACTORS.

Turning now to certain factors which might be supposed to be important
mainly as environmental influences, Goring studied the length of
imprisonment and the frequency of reconvictions for crime relative to
the periods of freedom as two measures of the degree of recidivism among
his criminal group. He measured the correlation between the degree of
recidivism and such outer factors as formal education classified by the
kind of school training, whether received in the elementary school,
secondary school, or at a compulsory industrial or reformatory school
for delinquents, also formal education as measured by the age at leaving
school; effective education as measured by the grade in school reached
at the time of leaving and by the educational grade assigned the convict
in the prison school; regularity of employment classified under the
headings regular, occasional, voluntarily unemployed, unemployable;
alcoholism under estimates as to the convicts' intemperance, temperance
or abstinence; family life, in which the standard of life was classified
as well-to-do, prosperous poor, poor, very poor, and destitute; the
influence of maternal authority measured by the age at death of the
mother, order of the subject in the family, and number in the family,
thus reaching the question of only sons and of size of family;
nationality; and finally the relation of age at which the first sentence
was received and the nature of the sentence to subsequent convictions.

The significance of the relation of these external influences upon the
degree of _recidivism_ is not directly comparable with the influence of
these factors upon the tendency to be convicted or not to be convicted
of crime at all, as he carefully explains. Since the distribution of the
above factors in the population at large is not known, the relationship
to criminality in general could not be measured for the outer factors as
it was for the inner factors discussed previously. Reserving, then, our
judgment as to how closely these environmental factors may be related to
the criminal tendency not represented by recidivism, we can reach
important conclusions as to their relation to the degree of recidivism.
Only one of the coefficients was found to be large enough to be twice
its probable error, so that as a whole they were not at all significant.
He summarizes his conclusions as follows:

  “The relative values of these contrasted coefficients demonstrate
  effectively and conclusively one truth: that an adverse environment
  is related much more intimately to the intelligence of the convicts
  than it is to the degree of their recidivism, or to the nature of
  the crimes they commit. Moreover, since mental defectiveness is
  closely related to crime, an easily imagined corollary to this truth
  is that the mental defectiveness of the convict is antecedent to his
  environmental misfortunes, rather than that his unfortunate
  circumstances have been responsible for the mental defectiveness of
  the convict, and his lapse into crime....”

  “From the general trend of the results tabulated above, our interim
  conclusion is that, relatively to its origin in the constitution of
  the malefactor, and especially in his mentally defective
  constitution, crime in this country is only to a trifling extent (if
  to any) the product of social inequality, or of adverse environment,
  or of other manifestations of what may be comprehensively termed
  'the force of circumstances'” (_20_, p. 287-288).

The caution which we have noted above, as to the influence of outer
factors having been measured in relation to recidivism rather than to
criminality, becomes more important when we find that the correlation of
high intelligence with frequency of convictions is also low, only -.16
and to fractions of a year imprisoned +.10. Since the relation of
intelligence to criminality in the general population is +.66, we cannot
be at all sure that these outer factors, or some of them, might not also
be much more closely related to criminality than they are to recidivism.
Besides this caution we might also urge that some of the most important
outer influences have not yet been evaluated by correlations. We know
nothing, as yet, except by inference about the correlation of
delinquency with the influence of bad companions outside the home, bad
school adjustment, the effect of broken families aside from the early
death of the mother, absence of proper recreation, and many other
stimuli for delinquency which social workers have been studying for
years by less conclusive methods.

Just to recall the frequency of some of these other conditions
associated with the environment of the youth we may note that
Aschaffenburg says that Abanel found in Paris “among 600 criminals under
twenty years of age in 303 cases the family life of the parents was
destroyed owing to death, divorce, desertion, illicit relations, or to
some similar cause” (_208_, p. 133). Again he states that in 1841 Father
Mathew, by making 1,800,000 total abstainers temporarily reduced serious
crimes in Ireland from 12,096 to 773 per annum in a period of three
years. Miss Rhoades by a personal evaluation of many factors involved in
each of 81 random cases of juvenile delinquency in Chicago found that
the main cause in 67 cases was some home condition and in 9 others it
was a special temptation in street gangs, while only in 5 was the main
cause mental subnormality (_171_). That nearly half of the juvenile
delinquents come from broken families, affected by death, divorce, or
desertion has been frequently shown. A study of more than a thousand
successive cases in the Minneapolis juvenile court by Miss Finkle showed
that 39% of them were from families not normally constituted, families
in which one of the natural parental guardians of the children had been
removed (_105_). We also have an important study of the relation of the
delinquent child to his home by Breckenridge and Abbot (_82_).

While there is always a possibility of finding some other factor closely
related to delinquency and independent of capacity, nevertheless we
should hardly urge this possibility at the present time as overweighing
the accumulation of negative evidence which has been assembled in recent
years, especially at the Galton Laboratory. We should remember that many
so-called outer influences are, like the temptation to drink, related to
the incapacity which precedes the temptations. There is also good reason
to suppose that many bad environmental surroundings result from rather
than cause deficiency. Even broken homes may be a result of incapacity,
to which undoubtedly early death is related. The first essential for
social philosophers is to recognize that so-called environmental factors
may have their corresponding inborn correlates. This is almost
invariable with home conditions. The problem is to weigh the relative
importance of these outer and inner factors on the same individuals.


Both subjective and objective methods have been used in trying to
determine whether heredity or environment has the most influence upon
criminality. The earlier and subjective method is one for which Gruhle
is perhaps the leading advocate. By this method an expert with wide
experience judges the relative effect of inner and outer causes of
delinquency in particular cases. In his study of 105 minor delinquents
in a German industrial school Gruhle, after a thorough and systematic
clinical and sociological study of each person, gave his judgment
whether heredity or environment was the main cause of delinquency in the
case. In his summary he concluded that in 9 cases the fundamental cause
was found in the environment, in 8 cases in environment plus a
subordinate influence of heredity, in 41 environment and heredity were
balanced, in 20 cases heredity was the main influence but environment
was a subordinate factor and in 21 heredity was considered the causal
factor. This shows that, when each case was estimated separately, in his
opinion heredity on the whole turned out to be more important than
environment for this group. By the same subjective method Gruhle weighs
the influence of family taints such as mental abnormalities, deficiency,
and drunkenness as against the hereditary influence in crime, and comes
to the surprising result that in 9 cases where both parents were
abnormal mentally or drunken in only two cases was heredity the
predominant cause of the delinquency, while in 7 cases where neither
parent showed these taints the delinquency was invariably explained by
heredity. The group whose delinquencies were in his opinion mainly due
to heredity showed, curiously enough, less family taints from nearly
every point of view. He concludes:

  “The knowledge that so many of the criminal youths are abnormal is
  indeed very significant for the therapeutic treatment of the social
  offenders, for the choice of the ways which should be used to
  improve the youths; but this knowledge has no significance for
  establishing the causes of delinquency.... The abnormal parents
  really have more children who are abnormal and under the average in
  capacity, but their children are actually more seldom delinquent
  because of the natural tendencies than the children of normal
  parents” (_121_).

Healy has followed a similar plan in subjectively weighing the influence
of various factors as causes of the delinquency of 823 recidivists
before the Psychopathic Institute at the Chicago Juvenile Court.
Although he does not directly estimate hereditary and environmental
factors as such, his summary of these estimates of separate cases shows
the main cause of delinquency in 455 of these cases to be some form of
mental abnormality or peculiarity. Abnormal physical conditions,
including excessive sex development accounted for 40 more. His other
causes, which embraced only 26% of the cases, might possibly be regarded
as directly environmental. They included defective home conditions,
including alcoholism, bad companions, mental conflicts, improper sex
experience and habits, etc.

Thus we find that the two most important expert estimates of individual
cases after exhaustive study apparently agree in placing the main causal
influence on factors which are predominately inner rather than outer.
The most serious objection to this method of approaching the problem is
that we have no way of determining how far such a result is the effect
of the expert's unintentional bias. Gruhle's analysis of his delinquent
group, however, raises very clearly the question whether the total
influence of heredity may not be markedly greater in the production of
delinquency than merely the heredity influence through mental deficiency
and abnormalities in the families.

A better method of evaluating the relative influence of heredity and
environment would avoid the danger of subjective bias by studying
objectively measured factors. With either the subjective or objective
method correlation affords a better way of statistically handling the
results. The best approach to an objective study of the inner and outer
causes of delinquency by the correlation methods is furnished by Goring.
The ingenuity of the biometrical procedure in applying correlation to
resolving this perennial question of heredity and environment must be
recognized by all who take the time to understand its methods. We can
only briefly consider the results of Goring's chapter on “The Relative
Influence of 'Inheritance' and 'Contagion' upon the Occurrence of Crime
and the Production of Criminals.”

This work conclusively demonstrates that crime runs in families. The
probable value of the correlation between conviction for crime on the
part of the father and son was found to be .60, while the correlation
between mother and son was only slightly less. The tendency to resemble
brothers in criminality was shown by the probable fraternal correlations
of .45. Whether this family resemblance is mainly through nature or
nurture is the problem.

In analyzing the influence of the home he uses partial correlation and
finds that the correlation between age at first conviction and the
number of convictions for a constant period of time after the first
conviction is -.243. “From the value and sign of this coefficient, we
see that the earlier in life a child commits a criminal offence, and is
consequently removed from his home, the worse criminal does he become;
and, accordingly, we conclude that criminal proclivities are more bred
in the home than inoculated there” (_119_, p. 368). This argues against
the predominant influence of the home training or example as explaining
_family resemblance_ in criminality. Nevertheless, it would seem that
the result might also be interpreted as meaning that the contact with
other delinquents and official discipline outside the home at a more
impressionable age notably increases the tendency to recidivism.

Besides the argument as to the earlier removal from home, we have a test
of the question whether those kinds of crime that are most influenced by
contagion show closer correlation within the family. His statement of
the results is as follows:

  “Our table 177, above, starting with crimes of fraud, passes to
  stealing and burglary—professional crimes, where the influence of
  criminal contagion should be the most intense; and then
  progressively to violence, arson and sexual offenses, in which last
  it is difficult to understand how the influence of example could
  have any effect at all. We can understand the influence of parental
  training in the original moulding of a professional burglar or
  thief, and, to a certain extent, it is conceivable that the constant
  spectacle of the lack of control in parents might lead their
  offspring to emulate them in acts of unlawful violence. But, that
  parental example could play any part of importance in the
  perpetration by their offspring of crimes such as arson and wilful
  damage to property, and, particularly, of sexual offenses, is not
  reasonably to be supposed. As seen in the above table, 177, the
  parental correlation for sexual crimes, and crimes for wilful damage
  to property is from .45 to .5; for stealing, it is from .48 to .58.
  We would assume then, from this evidence, that the tendency of the
  inherited factor in criminality is from .45 to .5, and the intensity
  of criminal contagion is anything between .05 and .1” (_20_, p.

Other evidence as to the relative influence of heredity and training,
which Goring suggests, is in connection with the difference in influence
of the two parents. If the contagion were from either the mother or
father alone, the difference in resemblance to that parent and the other
might indicate the strength of the contagion. The difference amounts to
about .05. This again, in his opinion, gives some idea of the relative
importance of nature and nurture within the family. The measure would
not be complete unless the hereditary tendency to resemble mother and
father were equal and the contagion were all from one parent.

Husbands and wives tend strongly to resemble each other in crime, the
correlation being .6378. This resemblance is of course not due to
heredity. Goring believes that it is not due to contagion and argues
that besides the subjective tendency for the criminals to associate
together, there is here a large element of conscious choice of a mate
among the criminal classes, especially as the criminal woman shows the
tendency most clearly and would not be able easily to get a non-criminal

This work of Goring illustrates how an important beginning has been made
in applying the correlation method to objective records, in order to
weigh the relative importance of hereditary and environmental sources of
crime. Perhaps its most important support is the close agreement between
his conclusions as to the importance of the native diathesis of
criminality and other studies by the biometric school as to the family
tendencies in physical traits such as stature, eye color, tuberculosis,
insanity, and deafness. These all tend to show a correlation between
parents and children or brothers and sisters of about .5 as compared
with relations to environmental factors which tend to be less than .1

                      (d) THE CRIMINAL DIATHESIS.

If one accepts the point of view that the cause of crime is to be
considered analogous to that of pulmonary tuberculosis, his
understanding of the etiology of crime gains immensely. The old question
of whether the criminal is born or made is answered, “both.” But the
emphasis from our present data is on the inborn tendencies. Moreover,
being born with the criminal diathesis does not mean that a person is
predestined to commit crime, but that he is more likely than his
neighbor to be infected by the contagion of delinquency. We have only to
catch the trend of recent scientific research to extend our vision
further. The criminal does not lack a simple unit character which would
otherwise make him whole as some of the disciples of Mendel seem to
argue. Neither is the criminal diathesis a simple instinctive tendency
like the tendency to make a specific response to a specific stimulus,
_e. g._, to wink when an object approaches the eye; the criminal is not
charged with a specific propensity to commit murder or to steal. The
safety of those who are more susceptible lies in keeping away from the
contagion of bad example and temptations to fall, toward which he is
generally less resistant than others. Specific training in strengthening
and guarding his weakest spots may in time build up a resistance to
temptations, the amount of which we cannot yet measure. His hope lies in
the recognition of his weakness and the adjustment of his living so that
his whole organism may support the breach in his make-up during the
struggle with himself and with society.

In this complex diathesis which means greater susceptibility to
temptations, there is little doubt that mental deficiency is the main
factor. Aschaffenburg has well expressed one effect of this particular
causal factor: “The weak-minded are generally children of the moment....
The lessons of experience, which serve normal persons as a guide, in
later events, soon fade, be cause they cannot be fitted into the
existing condition of the ideas. The inability to understand, much less
to form general points of view, is the direct result of mental weakness”
(_20_, p. 180). Lacking the ability to organize their experience, fixed
punishments have little restraining influence. Only prolonged training
and supervision can save them from being the victims of the moment. Even
the large majority above the grade of ability which would justify
indefinite supervision still show their stupidity in the offenses they
commit. Goring gives an instance of a watch repairer who was legally
punished nine times for pawning watches entrusted to him to repair. Who
would doubt that native stupidity is an important cause of the
recidivism which is so common a criticism of our present forms of legal
discipline? It is stated, for example, that 10,000 of those convicted in
one year in England had been convicted more than twenty times before
(_165_, p. 59). Even with school punishments the same association of bad
conduct and stupidity holds. Kemsies has shown, as quoted by Terman,
that the 16% ranking lowest in a group of pupils received 80% of the
punishments, while the brightest third received almost none (_194_).

That the criminal diathesis is not limited to mental deficiency is
demonstrated by Goring's results. He shows its smaller correlation with
deficient physical size, alcoholism and suicidal tendency with such
pathological conditions as insanity and epilepsy, independent of their
relations to mental deficiency. In this connection Gruhle's opinion that
the hereditary tendency to crime was greater among his non-defective
families may be borne in mind.

That mental ability, and especially mental deficiency, is primarily a
question of inherited capacity rather than training, is now indicated by
a number of fundamental objective studies of the correlation of
abilities within the family, which have been analyzed to show the
relative influence of inborn and external factors. Among these studies
Thorndike's investigation of the tested abilities of twins compared with
brothers and sisters in the same family is the most objective, and is
very convincing (_199_). He has also summarized the evidence so well
that it is not necessary to go into the question here (_198_). One of
the most important facts is that equal practise under the same
conditions increases the difference between individuals rather than
makes them more alike. The work of the English biometricians appearing
in Biometrika and the monographs from the Eugenics Laboratory is the
most important in this field, and cannot be summarized here. It includes
family resemblance in both pathological and healthy mental traits

As compared with these studies the attempt to show that
feeble-mindedness is inherited, because many of those in institutions
for the feeble-minded are from families showing mental taints, lacks
cogency, since we are still uninformed as to what portion of the
offspring of parents with and without deficient minds are deficient.
Even if 85% of the children in institutions for the feeble-minded have
tainted parents this does not mean that we know what percentage of
deficient parents have deficient offspring. It is this latter fact that
we must know in order to predict the danger of defective offspring from
deficient parents. From what we know about the correlation of parents
and offspring in mental ability, it is clear that the more deficient are
the parents, the more likely it is that their offspring are deficient.
Children of morons are, therefore, not so likely to be deficient as are
children of parents with lower grades of ability. From the eugenic point
of view, it is, therefore, most important first to protect society from
propagation by the lowest grades of deficients, provided that all grades
of deficients are equally likely to have children when left unrestrained
in society. Since mental and moral qualities are probably correlated
positively, the same emphasis would be placed on first isolating the
lowest grades in order to reduce inheritance of criminality. The eugenic
emphasis waits, however, on the discovery whether the greater tendency
for the lowest types to be produced by the lowest types is overbalanced
by any tendency of deficients or delinquents of lower degrees to be less
productive when unrestrained in society.

The conception of a criminal diathesis does not stop merely with the
notion that there is an inborn predisposition to crime. It considers
further that offenses do not occur except under the stimulus of certain
situations, even if such stimuli may be even more common than the
tubercle-bacillus. The important question which it now puts to science
is, “How much may the actual outbreak of delinquency be reduced with
better methods of social prophylaxis?” Even if, “the chief tasks of
social hygiene” are the “struggle against alcohol and against poor
economic conditions,” as Aschaffenburg believes (_68_, p. 228), the
chief emphasis from the best scientific work still seems to be that the
problems of alcoholism, poverty and crime are more closely related to
internal than to the external conditions which have thus far been
measured. Guarding against the propagation of mental deficiency thus
seems to be the most direct and hopeful method of attack, while the
removal of infecting temptations, and training for greater resistance,
should receive hearty, albeit subordinate emphasis.


Footnote 33:

  See the next section for the significance of these coefficients of


1. In our attempt to interpret the volume of results concerning tested
delinquents, we have accepted the common conception that the
feeble-minded are those who, through lack of mental development, are
_social deficients_. They cannot survive in society without supervision.
In the words of the English Mental Deficiency Act, “they require care,
supervision, and control for their own protection or for the protection
of others.” Our present scales of development tests do not detect those
deficients whose failure is not directly due to intellectual incapacity.
We have called those not detected by tests “purely conative cases,” to
distinguish them from the tested deficients, who were said to be
“intellectually deficient.” These conative cases would not be
feeble-minded except for their incapacity for prolonged acts of will.
Deficiency thus specialized in volition is so unusual, however, that the
study of tested deficients gives us a useful picture of the problem of
feeble-mindedness. To get a general view of the relation of deficiency
to delinquency we determined conservative borderlines with the Binet
scale and then reinterpreted on a common conservative basis the results
obtained in more than a score of investigations covering thousands of
objectively selected delinquents who had been tested. This has enabled
us very largely to remove the question of the frequency of deficient
delinquents from the realm of subjective opinion. We may now be certain
that under present conditions the problem of deficiency is most pressing
in institutions for female offenders. The evidence also points to the
greater frequency of deficiency among prostitutes and repeaters, rather
than among ordinary juvenile delinquents. We have thus been able to
restate the problem of the deficient delinquent more conservatively and
to modify some of the current conceptions. This enables us to direct our
efforts more intelligently, with greater foresight, and more hope of

2. A still broader outcome of this interpretative study is to increase
the precision of the test scales for use in the diagnosis of social
deficiency. This has been accomplished by an extended reconsideration of
the borderlines of deficiency on test scales, particularly the Binet
scale. A percentage definition of tested deficiency is suggested for
determining the borderline below which an individual may be presumed to
be so deficient as to justify isolation, and for setting off a distance
above this on the scale for which the test diagnosis of social
deficiency should be regarded as uncertain. By this means it is hoped
that the developmental scale may be made safer and more useful as an
instrument for diagnosing feeble-mindedness.

A quantitative definition for tested deficiency has its main
justification in its success in discovering social deficients and in
predicting social failure. With this in mind the percentages suggested
as representing the social deficients or uncertain cases in the
community were chosen after a careful search through the evidence as to
the success of children who had been in special classes or institutions
and an extensive résumé and analysis of the best expert estimates of the
frequency of social deficiency. The conclusion was that these
percentages may tentatively be placed so that those who would at 15
years of age be in the lowest 0.5% in tested ability among a randomly
selected group, may be presumed to be so deficient as to justify
isolation. Above these the next 1.0% may be regarded as uncertain, since
the bulk of them would require some supervision or guardianship during
life. These two borderlines have then been located on the Binet scale
for both the immature and the mature so far as possible from the
available data. In particular these borderlines for the mature have been
found for the first time on the basis of a randomly selected group.
Besides the records of Minneapolis delinquents these Binet borderlines
for a typical random population of 643 15-year-olds is the main
contribution of new data in the study.

The practical consideration of these borderlines in Part One and their
location on the test scale emphasizes that a test diagnosis is only
symptomatic, that the suggested borderlines on the Binet scale are
determined from limited data which may not be verified in other
communities, that the scale itself is imperfect, and that the results
should be checked by other tests, especially by the school retardation,
a new example of which is given for the Minneapolis delinquents. The
plan of the percentage method of describing the borderlines readily
allows for adjustment to more complete data or better developmental
scales. The alternative to the use of a test record as symptomatic of
deficiency is dependence upon the history of the case or physical signs,
such as are found among Mongolians, cretins, epileptics, etc. These
signs have been found among only about 13% of the deficient children
(_141_). Expert opinion given on the history of the case is clearly less
reliable than such opinion checked by even a crude objective test
standard. In Part Two of this study the theoretical background for the
percentage definition is compared with that of other quantitative
definitions on the basis of the conceptions of mental measurement and
mental development.

3. In attempting to suggest methods for diagnosis and control, which our
summary of the scientific data makes necessary, we shall be led beyond
the evidence presented in this study. To those to whom these suggestions
may seem remoted from the foregoing pages, it may be said that they are
the result not only of a review of the available research work, but also
an outcome of several years observation of the practical handling of
this problem both in this country and abroad. In that study I was led to
visit several scores of institutions and schools for delinquent or
deficient children in Austria, England, France, Germany, Italy and
Switzerland. The methods suggested below for the case of the deficient
delinquent are only modifications of what has been observed in actual

An adequate diagnosis of deficiency involves not only the accurate
knowledge of the present mental condition of the individual, but an
understanding of the causes of that condition. This requires a complete
family and social history of the individual and a knowledge of the
medically removable handicaps. It would seem, therefore, that such a
diagnosis may be best made by a commission which shall include a
physician as well as a psychologist, or else by an _expert in mental
development_ who is provided with adequate facilities and assistance for
discovering other handicaps than innate incapacity. For the group of
uncertain and conative cases a final diagnosis should, if possible, be
made only after prolonged observation in a temporary home school.

Frankfurt a. M. in Germany seems to have been the first to provide a
specialized observation cottage for uncertain cases among children. This
was established in 1900 and is much used by the juvenile court. Although
it has a separate building and an isolated division of the grounds it
is, however, connected with the local hospital for the insane. An
improvement in this respect was made with the first provincial school
for psychopathic children under compulsory training established near
Leipzig at Kleinmeusdorf. This serves also as a distribution station and
has two observation divisions through which all _fürsorge_ children in
the province pass. Only the psychopathic cases remain indefinitely.
Detention homes for juvenile delinquents in this country quite generally
are used for temporary quarters for cases to be observed, although these
are not isolated from the other children. If an entirely separate
observation institution is not possible, a more definitely recognized
probationary period for observation of the uncertain cases should be
arranged within other institutions. The efforts for clearing-houses for
mental defectives such as that in New York City and the Ohio Bureau of
Juvenile Research will help to distribute individuals to their proper
institutions. The ideal is a separate observation home where all cases
in which the question of mental deficiency and mental disease is raised
may be sent before the individual is labeled. The effect of commitment
to an institution for the feeble-minded, insane, or delinquent can be
guarded against much better if the observation home is entirely isolated
from all other institutions. The separate institution, however, is more
difficult to obtain than a separate division or cottage in an existing
institution. The latter forms a valuable intermediate step and is better
than merely giving uncertain cases additional attention when other
duties permit.

As a matter of legal procedure, diagnosis raises the troublesome
question of expert advice in court. Two decisions have to be made about
each case. First, is the individual deficient enough to justify
isolation or guardianship? Second, considering the means of care
available in the particular community, how should the deficient be cared
for? The first is primarily a question which requires expert knowledge
in mental development and should be so handled. The second decision
requires knowledge about the individual's home and about the facilities
for guardianship or isolation. It should be left with the authorities
thus informed. This will usually be the court unless there is a
commissioner or a committee especially charged with this duty.

An important advance in the legal definition of criminal responsibility
of deficients should be made by avoiding all subtle questions of
psychological analysis such as would be involved in deciding, for
example, under the New York statute whether the accused “was laboring
under such a defect of reason as not to know the nature and quality of
the act he was doing or know the nature of the act as wrong.” Obsolete
legal descriptions could easily be cleared away by adopting the
statement of the law suggested by the Committee of the Institute of
Criminal Law and Criminology for criminal responsibility and insanity.
In substance such a law would then state that the accused was mentally
deficient “so as not to be responsible ... for his acts or omissions at
the time when the act or omission charged was made.” The New York law
places an emphasis on knowledge which should be placed on will, only one
feature of which is an understanding of the situation.

4. What should be the aim in the care and control of deficients and
delinquents after diagnosis also depends upon a proper understanding of
the causes of these conditions. We have summarized some of the best and
most recent investigations in which a notable advance toward solving
this problem has been made by means of the correlation method. This has
proved to be a new and vigorous force for directing social progress. By
no other method have we approached so near the solution of the cause of
delinquency. It enables us to restate the problem of criminality as
mainly a problem in the treatment of a hereditary criminal diathesis in
which mental deficiency is the largest factor. These recent scientific
measurements have deprived neither the eugenist nor the euthenist of the
opportunity for service. There is plenty of congenial work to be done by
those whose sympathies may exaggerate the influence of heredity,
contagion, or training. As in the control of tuberculosis, so with the
diathesis of delinquency, some effect is produced by predisposition, by
training, and by external influences. Unless the present evidence,
however, is outweighed by improved data obtained in the future, the most
strategic point for attacking persistent delinquency is through the
relation to deficiency, with heredity holding the heights.

With the immediate campaign against delinquency centered against the
propagation of the social deficients, we have the atmosphere cleared so
that it is possible to turn attention to the best means of attaining
this end. Sterilization, isolation, or guardianship, by force or by
consent, which of these methods promises best? This is not a question
for detailed discussion here. We may, however, call attention to the
strides that have been made by such legislation as the British Mental
Deficiency Act of 1913 and to the summary of the laws of the several
states in our country published at the University of Washington,
Seattle. The question whether sterilization is desirable must at present
be settled apparently by the judgment whether the benefit in reducing
the propagation of the unfit outweighs the danger to morality through
the temptation of known sterility. The question of isolation of the
sexes by either sterilization or segregation resolves itself into the
question of accuracy of diagnosis and prognosis. Our review of the
uncertainties of diagnosis should make us cautious. When we consider the
social survival of many of those trained in the public school classes
for deficients and when a dozen girls discharged from the Massachusetts
institution for the feeble-minded succeeded in getting along in society
(_164_, p. 49), it would seem wise to place the emphasis on first
isolating those about whose danger to the community through delinquency
or propagation of deficiency there would be the least question. This
would mean those of uncertain mentality who were already repeated
delinquents or in imminent danger and those who were of the lowest
grades of deficiency, not the morons who were of uncertain moral and
mental ability. Among the clearly deficient there is no question but
that the emphasis should be to isolate first the girls and women of
child-bearing age, since their chance of obtaining mates is greater than
that of the deficient males. With doubtful cases public guardianship,
such as that provided by the British Mental Deficiency Act of 1913,
affords a promising remedy. Even those who are of uncertain ability
should, when in danger, be provided with whatever protection
guardianship can give. In this connection a suggestion of Dr. Goddard in
the Survey, March 2, 1912, may be utilized. A court in returning an
individual who is of uncertain ability to his family or guardian may
well warn them: “We shall leave him in your custody, but we insist that
you shall care for him, shall be responsible for him throughout his
life, shall see that he does not get into mischief, and above all that
he does not become a parent. Whenever the time comes that we find you
are incapable of performing or are neglecting this duty, then we shall
take him and place him in a colony.”

The question where to isolate the deficient delinquent, whom Kuhlmann
says is “equally well placed or misplaced in the institution for the
feeble-minded and the reformatory,” (_140_) is answered in substance by
Supt. Murdoch of the State Institution for the Feeble-Minded in Western
Pennsylvania. He suggests that in large states the deficient delinquents
might be cared for in an institution which should bear the same relation
to the state institutions for the feeble-minded and the penal
institutions as is now held by the asylums for the criminal insane.
Where a separate institution is not possible the affiliation with the
institutions for either the delinquents or the deficients may be tried
by means of colonies especially set apart in them. In Massachusetts
these divisions for the deficient delinquent are connected with the
institutions for delinquents.

5. Turning to external influences upon delinquency, we find that their
effect has been measured mainly in connection with the tendency to
repeat criminal acts. It has been shown by Goring that even such
important influences as the example of criminality in the home, kind and
amount of schooling, irregularity of employment, alcoholism, size of
family, low standard of living, early death of mother, etc., have
generally been found not to increase notably the tendency to recidivism
while they do correlate decidedly with deficiency. Nevertheless, it has
not been determined whether these external factors may not have an
important influence upon the first manifestation of the criminal
diathesis even though they tend only slightly to increase recidivism.
Should these external influences prove to be not more than a fifth as
important as deficiency and heredity, which now seems to be indicated,
we need to hunt for other outer influences which may really prove to be
more important.

Among bad external influences as yet unmeasured is maladjustment to
school among those of passable ability. We have given some evidence as
to this which we found among a group of delinquent boys at a county farm
school, when their test records were compared with their positions in
school. As a possible serious source of delinquency, bad adjustment to
school work should be studied further, since it is a matter that could
be easily corrected by the assistance of special teachers. With the
earlier discovery of deficient children by means of mental tests, it
should also be possible more definitely to direct the training so as to
build up resistance to worldly temptations. How much could be done in
this direction we cannot yet say. We have undoubtedly wasted much effort
in the past in trying to create intellectual capacity in those who are
innately deficient in intellect. Fortunately we are now directing our
attention to training them to acquire passable ability in simple
occupations, or to adjust themselves to the life of a colony. In the
education of the mentally weak the most promising field is undoubtedly
with the conative cases with passable intellects. At Templin, outside of
Berlin, there has been established the first home school devoted
entirely to the training of such unstable and inert boys. This
specialized institution for conative cases, which was founded by a
philanthropic society at the suggestion of Prof. Thiedor Ziehen, marks a
most important advance step in the problem of training the mentally
deficient. The results of specific training for the social adjustment of
the intellectually and of the volitionally deficient will be awaited
with great interest.

6. Shall the public authorities have the power to compel isolation and
special training at local or state schools? These powers have already
been provided by laws in a number of states. Thus far the law has not
outstripped scientific knowledge. How far the authorities should use
their discretion under these laws to force isolation is a question which
calls for the utmost good judgment on their part. In case the parents or
guardians of the socially deficient can be convinced of the desirability
of such isolation, this procedure is undoubtedly to be urged. When the
guardian has once consented to the isolation of his charge, he should
not be permitted to remove the individual from such care without the
consent of the proper public authority, which would of course be
reviewable in court. During this period of uncertainty as to the
prognosis of social deficiency, such a procedure would perhaps be
preferable to forced isolation in most cases, since the authorities
might be less troubled by the frequent annoyance of legal actions begun
by parents who had their children forcibly removed to institutions. In
some states unscrupulous attorneys have deliberately stirred up parents
to try to get back their children who had been taken away by force, thus
seriously interfering with the administration of laws for compulsory
isolation. Without the possibility of compulsory isolation of the
socially deficient for an indefinite time, we shall perpetuate the
disgraceful spectacle now observable in many states which cannot legally
prevent a feeble-minded parent removing a feeble-minded girl from an
institution to which she may be brought back a few years later with one
or more illegitimate, feeble-minded children. Our legal omissions should
not thus handicap the wisdom of society. The 1917 codification of the
Minnesota laws relating to defective, delinquent and deficient children
should be seen by those who are interested in the legal aspects of these
questions. It was brought about by the Minnesota Child Welfare
Commission, of which Judge Edward F. Waite was chairman.

7. In case we suddenly segregate for life all those who are so deficient
that we are justified in isolating them, would that solve the problem of
delinquency for the next generation? Although this would be the most
important attack which could be made on the most important known cause
of delinquency, we must still answer that the results would hardly be
comparable with a jail delivery. There is nothing to be gained by
turning our backs upon the facts. Goring has estimated that 7.2% of the
male population of England and Wales commit crime before death. We could
not possibly suppose that more than 1% of the male population could be
justly isolated for deficiency. Even if all the deficients committed
crime, at least six-sevenths of the criminals in these countries, about
which we have the best means of estimating, are presumably individuals
who could not be isolated for deficiency.

Moreover, Goring's estimates regarding the British convicts enable us to
judge that only about 25% of the criminals of this generation inherit a
predisposition to crime from parents who were the criminals of the last
generation (_20_, p. 336). Nobody has suggested isolating all persistent
delinquents. We could not expect that the isolation of both the
deficients and delinquents would completely remove the diathesis of
delinquency from society. The predisposition is received not only from
the deficients and delinquents, but also to some extent from those above
the borderlines. We could not raise the borderlines of deficiency
without isolating many whose social deficiency or delinquency it would
be presumptuous to predict. We should not look forward, therefore, to
the sudden elimination of the problem of delinquency even when it is
attacked at its most vital spot. On the other hand Dr. Hart, in a
bulletin of the Russell Sage Foundation, has worked out a practical plan
which would isolate the lowest 0.3% of the girls and women of
child-bearing age in this country within five to ten years. Some similar
plan for isolating all deficient delinquents would materially lessen the
cost of recidivism in the present generation.

The most hopeful sign is that we are no longer content merely to guess
at the relative importance of the sources of delinquency and deficiency,
but our efforts to promote social welfare are directed by scientific
investigations which are utilizing new and more efficient methods of



In defining the borderline of feeble-mindedness it will be found that
certain assumptions are usually tacitly made as to the form of the
curves of normal and retarded development. These assumptions which are
often based on vague conceptions of mental measurements should be
brought clearly to mind if we are to compare the relative merits of
different scales of mental tests or different ways of stating the
borderlines of deficiency. With this in view it is proposed to take up
in this second part of the monograph a brief technical discussion of the
units of mental measurement, the equivalent individual differences at
different ages, and the curves of mental development. The bearing of
these conceptions on the various quantitative definitions of tested
deficiency, including the percentage definition, will then be discussed
in the following chapter. Practical advice as to individual diagnosis or
group comparisons has been confined to Part One, so that those who are
not concerned with the theoretical assumptions on which the conception
of mental development and the interpretations of tested deficiency are
based should omit Part Two.

[Illustration: FIG. 3. _Hypothetical Development Curves (Normal

When we try to picture to ourselves the significance of individual
differences and mental development we are at once forced to think in
terms of graphs showing the distribution of abilities at particular
periods of life and the changes from one life-age to another. To
simplify the discussion I have presented in Fig. 3 the graphic picture
of the conditions on the simplest hypothesis, namely, that mental
capacity at each age is distributed in the form of the normal
probability curve extending to zero ability and that individuals retain
their same relative capacity on the scale of objective units.



In considering the curves of development it is desirable first to notice
the differences between measurement in equal physical units and
measurement in equivalent units of ability or of development. The
difference in the point of view of the two forms of measurement is so
pronounced that I can hardly hope to make myself clear to those who are
not somewhat familiar with such terms as “distribution curves,”
“frequency surfaces,” “standard deviation,” and other phrases connected
with the theory of probability, which are treated at length in such
books as Thorndike's “Mental and Social Measurements” and Yule's
“Introduction to the Theory of Statistics.” We often, by mistake, regard
the growth of an inch in height, for example, as always representing an
equivalent unit of growth. This will lead us into rather serious
misconceptions unless we are careful, for it is perfectly evident that
the growth of an inch in height has a very different significance for
the three-year-old boy than for the eight-year-old. Half of the
three-year-old boys grow about 3 inches during a year while at eight
years of age not more than about one in seven grow that much. Moreover
it is not always satisfactory to regard the same _relative_ increase in
physical size as an equivalent unit of development. To say that a boy 20
inches tall who grows 1-10 in height shows an increase in development
equivalent to a boy of 50 inches who grows one-tenth, may be quite
misleading. Nearly every 20-inch child grows one-tenth in height in a
year while not one in fourteen of the boys who are 50 inches in height
may grow at that physical rate. In considering human traits, and
especially developmental traits, it would seem to conduce to more
significant thought if we gave up at times our habit of thinking in
terms of equal or relative physical units and thought instead in terms
of more equivalent biological units.

In the measurement of mental ability, moreover, it is exceedingly
difficult to utilize equal physical units. Most of the objective units
which are commonly called alike are clearly not equal even in the
physical sense. “Spelling one word,” for example, is not equal to
spelling another “one word;” but only equal to spelling the same word.
Out of such units of amount accomplished, it is, of course, not possible
to build a satisfactory scale without referring to some other concepts
of measurement. Some tests, however, are scored in equal units. When the
measurements for example, are in the units of time it takes to perform
the same task under the same outward conditions we have the possibility
of a scale of equal objective units. Such a scale is approached by the
results with the form board test which give the number of seconds it
takes children to place blocks of different shapes in their proper

Even the unit of time may be deceptive in name, as it is with the Binet
scale. A year of time is, of course, the same physical unit and the task
proposed with the Binet scale is always the same, but the other
essential with this scale, the children of each age who pass the tests
at each age norm, varies decidedly. “Test-age five,” for example, means
44% of the children pass and “test-age eleven” means 88% pass, even with
approximately random samples of children of these life-ages. This
question of the equality of the Binet age units will have to be
considered further, therefore, in connection with the other concept of
equivalence used in psychology.

In order to determine equivalent units of activity we find that a number
of different concepts have been utilized. With some of the scales for
measuring educational products, such as Thorndike's Scale for
Handwriting, equal units of merit in handwriting mean differences judged
equal by relatively the same proportion of competent judges. This form
of unit has not been used, however, in any scale of mental development
thus far proposed.

In the measurement of mental ability the most commonly accepted idea of
equivalent units is that they are provided by the units of standard
deviation for a series of measurements which distribute in the normal
form. The meaning of these units may be understood by referring to Fig.
3 which shows Gaussian or normal distributions of abilities of
individuals at various periods of life in curves A, B, C, D and E. The
straight lines of the measurement scales form the bases of these
distribution curves. These graphs represent the normal form of
distribution usually expected when any fundamental ability is measured
in a random group. If the number of cases at each unit of measurement
are plotted by a point placed relatively as far above the scale, used as
a base line, as the number of cases found at that unit of the scale, it
will be discovered that these points arrange themselves in the form of a
symmetrical curve high at the middle and flaring out along the base-line
scale. This bell-shaped curve, known as a normal probability curve,
shows that the largest number of cases occurs at the middle or average
measurement. From this middle point on the scale the number of cases
falls off gradually and symmetrically in both directions. Distances
along the base line of this distribution surface may then be measured in
terms of the standard deviation regarded as unity. This S. D. is the
best measure of the scatter of the deviations. It is the square root of
the average of the squares of the deviations of the separate
measurements from the average of all the measurements. There are
approximately four units of the standard deviation between the average
and either extreme when the distribution is normal, as in Fig. 3. Only
six cases in one hundred thousand fall outside these limits.

The studies of biological traits suggest that a unit of the standard
deviation is the most important measure we have for equivalent degrees
of any trait which distributes normally. It measures the same portion of
the total distance from the lowest to the highest ability on any
objective scale so long as the distribution of measurements is in the
_normal_ form. It thus affords the best interchangeable unit from
measurements at one life-age to those at another, provided that the
distributions keep close to the form of the normal probability curve.
This is the assumption on which practically all the developmental scales
have been based. The difference in ability between an individual at the
average and at -1 S. D. (standard deviation) below the average is
equivalent to that between the last individual and one at -2 S. D. The
same distances along the base line of different distribution surfaces
measured in terms of their respective deviations set off equivalent
portions at each age so long as the distributions are normal. For
example individuals measuring between -2 and -3 S. D. in any
distribution in Fig. 3 are equivalent in ability to those lying between
-2 and -3 S. D. in any other of these normal distribution surfaces.
Later we shall consider equivalent units when the form of the
distribution of ability is not normal or is unknown.

We may now compare the relations of the units in the physical scale,
shown at the left of the figure, to units of the scales for adults or
for the immature of any age, expressed in units of the standard
deviation from the averages of these groups. Relative ability measured
on the physical scale or any one of the distribution scales in Fig. 3
will be found identical since they all start from the same zero point
and the distributions are all normal. But the ability of an individual
in one distribution can hardly be compared with that of an individual in
another distribution in a biologically significant way by their actual
positions on the physical scale. A physical unit, does not measure the
same sort of fact of development in a scale for the immature that it
measures in the scale for adults or that it measures in another dynamic
scale for the immature. This can be seen when a physical unit is
compared with the amount of standard deviation which it measures in the
different scales. Moreover, the correspondence of relative distances on
the physical scale and any one of these other scales will not hold the
moment the distributions do not start from the same point or are

It does not seem seriously wrong to suppose that there are some
individuals at any age who have no more mental ability than the baby of
the poorest mental ability at birth. At any rate our intelligence scales
are hardly fine enough to measure the difference in intellectual
capacity between the dullest adult idiots and the dullest idiot babies.
We shall, therefore, here assume that mental capacity extends to zero at
each age. The importance of this will be evident when we consider the
question whether the distributions of ability are symmetrical around the
average point at each age. Postponing for the present the discussion of
unsymmetrical or skewed distributions, we may consider the several
meanings of stages of development.

In applying the concept of the probability curve we should distinguish
between individuals who have attained their mature mental capacity and
those who are still maturing. The former would be represented by a
random group of adults (Distribution E, Fig. 3) the latter by a group of
nine-year-olds (Distribution C). If we say, for example, that a child
has reached a certain stage of development we might have in mind the
final distribution of mature capacity or the distribution of capacity
among those of his particular age or of all ages. When we compare stages
of development we must, therefore, be careful to indicate the
distribution surface to which we are referring.

An increase in development may refer to at least five different things
depending upon the scale of measurement to which reference is made.
Besides an increase measured by the physical scale, the scales for
adults, for the immature or for all ages, to which we have already
referred, it may mean an increase judged by the distribution of
increases which individuals of the same life-age and capacity make in
the same period of time. This last meaning may be the most significant,
although it has never been used. It has reference to a distribution
surface of _increases_ such as is represented in Distribution F, Fig. 3.
This is intended to show the increases in one year of all two-year-old
children who had average ability at 2 years, on the assumption that at 3
years these children would on the average equal the average of all
three-year-olds. It is clear that when these increases are measured in
objective units the latter have a still different significance from that
assigned to them in connection with other scales. An increase of one
objective unit here might represent twice the standard deviation, while
it only represents 0.2 of the standard deviation in another

                 (b) THE YEAR UNIT OF THE BINET SCALE.

A sharp disagreement of opinion as to whether the Binet year units can
be regarded equivalent has arisen between Karl Pearson, Director of the
Galton Laboratory in London, and certain psychologists who have used the
Binet scale. Cyril Burt, for example, says, as quoted by Pearson:

“Except for rough and popular purposes, any measurement of mental
capacity in terms of age is unsatisfactory.... The unit fluctuates in
its significance all along the scale. When the child is just beginning
to walk and talk, when he is 7 or 8, when he is 10 to 11, when he is on
the verge of puberty—at these different periods a retardation of a
single year means very different things” (_164_, p. 36).

A number of good psychologists including Yerkes, Terman, and Kuhlmann,
agree with Burt in maintaining that a year of retardation at different
ages has very different significance.

With this statement of Burt, Pearson takes issue, saying:

“Can the psychologist to the London County Council ever have seen the
growth curves of children, or would he write thus?... There is no valid
reason to suppose that a year's growth in mental power may not be taken
for all practical purposes to mean the same unit for ages of 6 to 15,
the period for which Binet and Jaederholm have used the tests” (_164_,
p. 44).

Like many other apparently opposite statements both contain truth. The
conflict arises apparently, first from a disagreement between the data
obtained with the Jaederholm form of the scale, on which Pearson bases
his statement, and data obtained with other forms of the scale; second,
from a discrepancy in the points of view. Pearson stresses the fact that
the mental year-marks equal average growth increment with the Jaederholm
scale (_167_). He shows that the regression of years of mental excess
(or deficiency) on increase of life-age is a straight line, just as he
found it with physical measurements. Moreover, the standard deviation of
the mental measurements for the entire group of normal school children,
6-14 years of age, was found to be about one year of mental age (.96
year for the corrected data) (_167_). To which Pearson's opponents might
reply, these facts are of comparatively little significance unless the
_deviations for the separate ages_ are alike in terms of these year
units on the scale. Neither linear regression nor the balancing of years
of excess by years of deficiency at each age indicates that the
deviations of the separate ages are alike in terms of the year units.
The new Stanford scale, for example, shows both of these conditions and
yet the range of months of life-ages which sets off the middle 50% of
the children of the different tested ages increased decidedly from 6 to
14 years of age. The middle half of the tested ages, for example, at age
VI on the scale include a randomly selected group of six-year-old
children whose range of life-age is ten months, at age VIII on the scale
this range is 13.4 months, at X it is 16 months, at XII, 20 months, and
at XIV, 26 months. “The number of 6-year-old children testing 'at age'
is approximately twice as great as the number of 12-year-olds testing at
age, and 50% greater than in the case of the 9-year-olds” (_196_, p.

To this argument Pearson might reply that he had not overlooked the
question of variation in the deviations from one age to the next for he
has a footnote in which he states regarding the Jaederholm data: “There
are, however, relatively little differences in these mental age
standard-deviations of the normal children beyond what we may attribute
to the effect of random sampling” (_164_, p. 46). In this respect, then,
the Jaederholm data differ notably from Terman's data obtained with
random groups with the Stanford scale and, as I shall show, from data
obtained by Goddard with the 1908 Binet scale, the two largest groups of
Binet test data which have been collected. Even with the Jaederholm data
on efficient school children, although the largest difference between
the standard deviations of different age groups is only about twice its
probable error, it is notable that 24 of his 39 7-year-olds are included
within an interval of the middle year of tested age, while only 9 of his
35 11-year-olds are included within the same middle year interval.

Taking Goddard's data for the 1908 scale for the separate ages from 5-11
at which probably the factor of selection for his groups may be
neglected, I have calculated the standard deviations from his Table I
and find them as follows:

                                     │            Life-Ages
                                     │ 5  │ 6  │ 7  │ 8  │ 9  │ 10 │ 11
 Standard deviations in Mental Excess│1.10│.98 │.93 │.99 │1.04│1.23│1.19
   or Deficiency                     │    │    │    │    │    │    │

The differences between the deviations for ages 7 and 11 or between ages
8 and 10, are more than three times their standard errors, so that we
would not be justified in assuming that the standard deviations of the
separate ages measured in terms of years of excess are equivalent. There
seems to be a tendency for the deviations to increase, at least from age
7 to 10 and 11.

The comparison of the year units on the Binet scale with the diagrams in
Fig. 3 shows that if the scale at each life-age shut out the same lowest
proportion, say half, of the children of that age, then the year units
might be regarded as equal in the sense of equal average growth
increments, as Pearson suggests. A child 7 years of age testing VII
would be at least one annual average-growth unit higher in mental
development than one of 6 years testing VI, and so with each age until
the limit of development had been reached. This is the condition
approximated closely for children by the new Stanford scale and the
corrected Jaederholm data. Since there is little prospect, however, even
with a scale perfected so far as its age norms are concerned, that the
total distributions for each of the different years would be the same
multiple of the year-units, the main significance of the age units is in
permitting the statement that a child had reached the tested development
normal for the children of a certain age.

It is also legitimate to use years of retardation as a short way of
expressing rough borderlines when they happen thus to afford an easy
method of empirically describing equivalent borderlines for a particular
scale. This is what I have done for convenience in Part One of this
book. I certainly do not mean to contend that four-years retardation has
theoretically the same significance at different ages, in terms of the
deviation of the separate ages. To me the Binet years are no more than
names for certain positions on the scale.

To most psychologists who have been dealing with the measurement of
mental development, I believe that the most significant concept of
equivalent units would be in terms of the deviations for each age
provided that the form of the distributions remained normal. But the
deviations vary so much in the terms of the year units that it is not
likely that they will be willing to accept a _year of excess or
deficiency_ as an equivalent unit for different ages with the common
forms of the scale in use in English-speaking countries. Moreover, below
the age of 6 and above 15, the limits which Pearson discusses, there is
good reason to expect the year unit to vary still further. This Pearson
recognizes for the complete developmental curve. It is only at the
intermediate years, in which the average increases are most constant in
relation to the deviations of the separate ages, that the year unit may
be at all serviceable in measuring the deviation of a child from the
norm of his age.

With the scales in use in this country the Binet year units are not
equivalent in the sense in which they are usually spoken of as
equivalent. We should recognize this and emphasize it. Even if the norms
at each age marked off the same proportion of the individuals, as shown
in A and B of Fig. 4, unless we knew that the forms of distribution were
always alike, we should not know that the distance between successive
age norms was the same on any sort of objective scale other than average
age increments. Moreover, we would not have an objective scale of equal
units applicable to measuring the deviation of children of any one age.
The average annual increments would not necessarily represent the same
proportion of the total distance from the lowest to the highest ability
at different ages even if the distributions were all normal. With normal
distributions it would also be necessary to demonstrate empirically that
the annual average growth increment between successive ages always bore
a constant relation to the deviations at these adjacent ages as shown in
B of Fig. 4 where the increment is equal to 1 S. D. at each age. This
could not possibly hold when the increment lessened near maturity.

[Illustration: FIG. 4. _The Question of Equivalence of Year Units._]

If the distributions of ability were variously skewed, the year units of
excess or deficiency would not be shown to be equivalent at the
different ages even if the proportion of individuals one year
accelerated was equal to the number one year retarded, two years
accelerated equal to those two years retarded, etc., at each age and the
norm at each age shut out the same proportions of the age group. This is
shown in C of Fig. 4 in which the year units are clearly not equal steps
from lowest to highest ability even for the same age and yet the usual
criteria which have been suggested for discovering the equivalence of
the units are fulfilled. Whether the actual distribution of ability is
skewed or normal cannot be determined by the Binet scale, of course, on
account of the uncertain and probably varying size of its year units in
measuring deviations at any age.

With the empirical evidence against the equivalence of the year units
and the impossibility of determining their equivalence unless we first
know that ability is distributed normally at each age, it is certainly
hazardous to assume that individual deviations measured in terms of year
units are equivalent at different ages.

It may be noted that it is quite as hazardous to suppose that the units
of the Point scale are equivalent in any theoretical or practical sense.
This question will be discussed later in Chap. XIII, B, (b).


Before leaving the question of the significance of units on a scale
described in terms of the standard deviation we should ask whether
tested mental abilities have been found to distribute normally, _i. e._,
in the form of the symmetrical Gaussian curve with each extreme the same
distance from the middle measurement. Contrary to the usual supposition
in this matter, it seems as if the evidence was somewhat against this
assumption, although neither position can be asserted at all
dogmatically on the basis of our present data. A résumé of this evidence
which I have given below makes it appear that the assumption of a normal
distribution will not conflict with a practical use of normal
probability tables for medium degrees of ability, but may quite
seriously interfere with such use for the borderline of deficiency.
There is little doubt, as Pearson believes, that the bulk of the
children now in special classes for the retarded in the public schools
would fall within the lower range of a normal distribution fitted to the
general population. On the other hand, there is likely to be a
respectable minority of the deficients which will be beyond such a
normal curve. These facts are sufficiently evident, I believe, to make
it impossible to base quantitative descriptions of borderline of
deficiency on a hypothesis of normal distribution.

The best evidence on this point is probably the data of Norsworthy with
eleven tests on groups of 100 to 150 feeble-minded children in
institutions and special classes and 250 to 900 normal children. She
expressed the position of each child in terms of the deviation of the
group of normal children of his age for each test. Pearson has presented
her data graphically on the assumption that her defective group
represented 0.3% of a general population of 50,000 children, and then
fitted a normal distribution curve to her data with her normal group.
The result makes it evident, especially for the intelligence tests, that
the defective group would better be described as part of a skewed
distribution. To less extent this is also true for the maturity and
memory tests (_15_, p. 30). Norsworthy's own table of data show that 43
of the 74 feeble-minded taking the intelligence tests were over -5 times
the probable error of their ages below the averages of the normal
children, a criterion which she proposes as indicating ability outside
of that included in the normal species. Moreover, 9 children score
between -22 P. E. and -32 P. E. which is far beyond any conceivable
extension of the normal curve. Her figure for the composite results of
all her mental tests is also manifestly skewed toward deficiency
although she hesitates to adopt this conclusion, and was content with
showing that they grade off into the distribution of normal children.

The other data, which I have found, that indicate that tested ability,
when measured in equal physical units for the same task, is skewed
toward deficiency, have to do with tests that are pre-eminently for
psychomotor activities rather than intellectual. They consist of
Sylvester's and Young's results with the form board test on Philadelphia
school children, Stenquist's results with his construction test, and
Smedley's results with the ergograph test on Chicago school children.
Here we may apply the better criterion of the distance of the quartiles
above and below the median of the group. These positions would be less
likely, through extreme records, to be affected by chance conditions
during the testing.

It is to be remembered that if the records of school pupils appear to be
normally distributed this would not settle our problem, since it is
apparent that idiots and many imbeciles are not sent to the public
schools at all. The lowest children at any age would not be represented
in the regular school groups. On the other hand, the brightest children
are not generally drawn away from the public schools at least before 14
years of age in this country. We shall confine ourselves, therefore, to
school-children 6-13 years of age. If we find that they show ability
skewed toward deficiency the results will underestimate rather than
over-estimate the skewness.

Sylvester (_191_) tested with the form board a group of 1537 children in
the Philadelphia public schools, from 80 to 221 at each age from 5 to 14
inclusive. “Except that no especially backward or peculiar children were
included there was no selection.” This study gives, with the complete
distribution tables, the number of seconds required for the same task by
the children at each age. If we find that the limit of the lower 25
percentile was farther from the median than the limit of the upper 25
percentile we can be reasonably sure that the difference would be still
greater if the excluded deficient and backward children were also
included. By calculating the quartiles and their differences from the
medians at each age, I find that for only two of the eight ages is the
upper quartile farther from the median than the lower quartile. The
average excess of the distances of the lower quartile is .64 of a
second. At only age 7 is the difference three times its probable error,
2.1 seconds, P. E. .67. The form board distributions thus tend to be
slightly skewed toward deficiency. The errors of the quartiles were
found by the method given in Yule's _Introduction to the Theory of
Statistics_, Chap. XVII, which assumes normal distribution, so that they
are too small. The skewness is more manifest when the extreme
measurements are compared with medians at each age. It is not possible,
unfortunately, to compare his group of normal children with those in the
special classes since he did not use the same method of giving the test.

Since it was not important to compare the amounts of skewness in
different data, I have not attempted the more elaborate calculations of
coefficients of skewness. These would give the results a more elegant
statistical expression. The simpler method I have here used affords more
convincing evidence of asymmetry for the non-mathematical reader.

Young has published the results with Witmer's form board test on
approximately two hundred Philadelphia children for each age, giving the
results for the sexes separately for each half year of life-age (_227_).
This affords 36 different groups in which he gives the median and upper
and lower quintiles for the shortest time records. The lowest quintile
is farther from the median in 25 cases, equal in 6 and less than the
upper quintile in only 6 of the 36 comparisons. This skewness would have
been even greater if children of the special classes had not been
excluded from his groups.

Stenquist's results (_54_) with his construction test are scored in
arbitrary units in which allowance is made for the quality of the score,
but we should expect no constant effect on the form of the distribution
from the character of these units of measurement. At ages 6 to 13 he
tested from 27 to 74 pupils randomly selected from the public schools, a
total of over 400. For six of these eight ages the lower quartile is
farther from the median than the upper quartile, when calculated from
his distribution table. The number of cases at each age, however, is so
small that the largest difference, 15 units, is not three times its
probable error, 6.

Smedley gave his ergograph test to about 700 school children of each of
the ages we are considering. Since he tested so many more subjects than
any other investigator this should provide the most valuable data on the
question of distribution with a test recorded in the same physical units
for the same task. Unfortunately, his results for two succeeding years
are so directly contradictory to each other that they seem to have no
significance for our problem. The simplest explanation of this
contradiction is that the groups tested may have been selected on a
different basis each year.

  A casual observation of his standard percentile curves for the
  ergograph test at the different ages gives the impression that the
  distributions are decidedly skewed toward deficiency, but this
  impression is not justified by a careful analysis of his results
  (_51_). In the table which accompanies his standard percentile
  curves, giving his total results for the two years, we find that
  there is a sharp disagreement between the distributions of the
  boys and the girls. The distributions for the boys at each age
  between 6 and 13 years show a greater distance, measured in
  kilogram-centimeters, from the median to the 80-percentile than
  from the median to the 20-percentile, in 5 ages out of 8. The
  total difference is also slightly greater between the median and
  the upper 80-percentile. On the other hand, the table for the
  girls at these ages shows the 20-percentile farther from the
  median in 5 out of 8 ages, with a total difference considerably
  greater than that shown for the boys. Usually the differences were
  small compared with their errors. With the boys only at age 13 was
  the difference in favor of the 80-percentile three times its
  probable error, while with the girls the four oldest ages show the
  distance of the 20-percentile greater by three times its probable

  A comparison with the reports of Smedley on this test for the
  previous year (Report No. 2), leaves his results still more
  uncertain. While he does not give the medians at each age, we may
  make less satisfactory comparisons between the distance of the
  10-percentile from the 25-percentile and the distance of the
  90-percentile from the 75-percentile. If we do this, we find the
  distance is uniformly greater at the upper end of the distributions
  for each age both for the boys and girls. The Smedley results are,
  therefore, decidedly contradictory. The first year shows
  distributions skewed toward excellence and total results for two
  years show distributions skewed mainly toward deficiency.

Broadly considered, the Binet records with school children point to a
skewed distribution toward deficiency when large allowance is made for
the difference in value of the year units. It is extremely rare to find
a child testing 4 years in advance of his life-age, while 15-year-old
idiots are presumed to test 12-year-units or more under a mature

Pearson believes that “the Gaussian curve will be found to describe
effectively the distribution of mental excess and defect” for
intermediate ages as measured by Jaederholm's form of the Binet scale.
The data on which Pearson places reliance are Jaederholm's results in
testing 261 normal children 6-14 years of age in the Stockholm schools
and 301 backward children in the special help classes of the same city.
The best fit of a normal curve to the data was obtained with a group of
100 8-year-old children, in which case the chances were even that
samples from a normal distribution would fit. With his larger normal and
backward groups combined in proper proportions in one population the
chances were 20 to 1 that such a distribution as was actually found
would not fit into the Gaussian distribution. He admits that “this is
not a very good result,” although it is better than when the Gaussian
curve is fitted to either the normal or the backward group alone. In a
subsequent paper he gives each child a score relative to the standard
deviation of the normal child _of his own age_, a method comparable to
his treatment of Norsworthy's data. He then finds that “10% to 20% or
those from 4 to 4.5 years and beyond of mental defect could not be
matched at all from 27,000 children” (_164_, p. 46). In each case the
distributions actually found were skewed somewhat toward deficiency.
Furthermore, when he suggests that -4 S. D. may be used as a borderline
for tested deficiency, he recognized that the mental ability of children
is skewed so far as the empirical data are concerned. With a normal
distribution there would not be two children in 100,000 who would fall
below this borderline. Nevertheless, the normal curve serves for most
practical purposes to describe the middle ranges of ability.

Pearson thinks that the skewed distributions of his data may possibly be
explained by the drawing off of older children of better ability to the
“Vorgymnasium,” or to the higher-grade schools, by the incompleteness of
the higher age testing, or by the “possibility of the existence of a
really anomalous group of mental defectives, who, while continuously
graded _inter se_, and continuously graded with the normal population as
far as intelligence tests indicate, are really heterogeneous in origin,
and differentiated from the remainder of the mentally defective
population” (_164_, p. 34). The last hypothesis, of course, supposes
that mental ability is skewed and suggests the cause. He supplements
this explanation by stating that the heterogeneous cause of the “social
inefficiency” of the deficients may not be connected directly with the
intellect but affect rather the conative side of the mind. A skewed
distribution under biological principles of interpretation supposes a
single cause or group of causes especially affecting a portion of the

It is also to be noted that the apparent form of distribution may be the
result of the nature of the test and the units in which it is scored.
Some tests might not discriminate equally well a difference in ability
at the lower and at the upper ranges of ability. If the test were too
easy the group might bunch at the upper portion of the scale and the
distribution appear to be skewed toward the lower extreme where there
were only a few cases. If too difficult a test were used the form of
distribution might shift in the opposite direction, most of the group
ranking low. It is extremely difficult to formulate mental tests so that
they will equally well measure differences at each degree of ability.
This objection should not hold, however, if the scoring were in units of
time for the same task, as with the form board test. The essential
characteristics of a test in order that it may indicate the form of a
distribution is that the units of scoring shall be objectively equal
under some reasonable interpretation and that they shall be fine enough
to discriminate ability at each position on the scale. Under such
conditions the variations in the difficulty of tests should not obscure
the form of the distribution of the ability tested.

Turning to the analogy of measurements of physical growth, a strong
argument may be made for the hypothesis of shifting forms of
distribution. As Boas points out regarding measurements of the body at
adolescence, owing to the rapid increase of the rate of growth the
distribution of the amounts of growth is asymmetrical, “the asymmetry of
annual growth makes also all series of measurements of statures,
weights, etc., asymmetrical.” Moreover, “acceleration and retardation of
growth affects all the parts of the body at the same time, although not
all to the same extent.... Rapid physical and rapid mental growth go
hand in hand” (_80_). There is no reason to suppose that the brain is
free from this phenomenon of asymmetrical distribution of annual
increments of growth among children of the same age when the rate of
growth is changing as at adolescence. It is therefore to be expected
that the separate age distributions would be skewed at early ages and at
adolescence even if the distribution should be normal with a static
population. The presumption from physical measurements is that the form
of distribution shifts with age.

Again we may note that if some of the idiots reach an arrest of
development before any of the normal individuals, as several
investigators contend, this would imply that the distributions must be
skewed unless there is a curious corresponding acceleration of growth on
the part of geniuses to balance this lagging by idiots.

In spite of these arguments and the evidence of asymmetry of
measurements at least at some periods of life it is to be noted that
current opinion is probably contrary to this hypothesis, although, as I
believe, because it has been concerned mainly with those who are not of
extreme ability. For all large medium ranges of ability slight skewness
might well be negligible. It is interesting to note that Galton says
that “eminently gifted men are raised as much above mediocrity as idiots
are depressed below it” (_159_, p. 19). Measured by intelligence
quotients with the Stanford scale, Terman finds among school children
that deviations below normal are not more common than those above
(_197_, p. 555). Burt, following a suggestion of Cattell as to college
men, however, seems to incline to the opinion that the general
distribution of ability, like wages, is skewed toward the upper end. He
adds, “In crude language, dullards outnumber geniuses, just as paupers
outnumber millionaires” (_85_).


For our problem of units and scales of measurement, an asymmetrical
distribution sets a very difficult problem. It may be that this very
difficulty has been one of the main reasons for slowness in recognizing
the drift of the evidence. In order to set forth the difference in the
conception of measurement when distributions become asymmetrical I have
presented this hypothesis in connection with the curves of development
in Fig. 5. It will be noted that if the distributions of mental capacity
vary in symmetry, the units of standard deviation change in significance
from one form of distribution to another. Minus 2 S. D. may exclude very
different portions of groups differently distributed, while it would
always exclude the same proportion if the distributions had the same
symmetry, or skewness.

Under conditions of variable symmetry there is a sense in which the same
relative physical score in units running from zero ability to the best
ability would always have an equivalent objective meaning, but this
might not express equivalent development conditions at different ages.
For example, with shifting forms of distribution, to say that a child of
six years had reached three-fifths of the best development for his age
on an objective scale might give no significant indication of how nearly
he was keeping pace with those three-fifths of the best ability of
another age. Neither would his position in units of the deviation of
ability at his age give this information without knowledge of the form
of the distribution of ability at his age. With varying forms of
distribution at different stages of development this would afford an
insurmountable difficulty.

[Illustration: FIG. 5. _Hypothetical Development Curves (Changing Forms
of Distribution)_]

With unknown or varying types of distribution it is desirable to utilize
percentiles as equivalent units for comparing individuals at different
stages of development. They differ somewhat from ranks in an order of
noticeable differences. With an indefinitely large group, such ranks
would mark off only those cases which were indistinguishable in merit.
These units would be numbered in order from the highest to the lowest in
ranks of just distinguishable merit, a different number of individuals
conceivably occurring at the single steps. Psychologically the
percentiles are somewhat less significant because they are not
conceivable in steps of just noticeable differences. Percentiles have
less value in _comparing abilities in the same distribution_, but have
decided advantages when _comparing corresponding abilities in different
distributions_. Except at points where merit is indistinguishable, they
signify that a certain proportion of a group is ahead in the struggle
for existence. They are thus units of relative rank. Moreover, they are
directly translatable into units of the deviation in case the form of
the distribution of ability has been determined. This is a special
advantage if the forms of distribution turn out to be normal or even

In using percentiles it is to be remembered that equal differences
between percentiles _are not comparable in the same distribution_ except
in the sense of the same extra proportions of the group to be met in
competition. A change in the degree of ability from the lowest
percentile to the lowest 2 percentile would be very different from the
change in the degree represented by the 50 percentile to the next
percentile above. Differences in the ability of individuals ranking near
each other in the middle of the same percentile series would be
distinguished with difficulty while it would be easy to make such
discriminations at the extremes.

The special value of the percentile units in measurement of ability lies
in the comparison of individuals of corresponding position in
corresponding groups in which the ability may not be assumed to
distribute alike. The concept that 995 out of every 1000 randomly
selected individuals at his age are ahead of a particular individual in
the struggle for existence has very definite and significant meaning
which is quite comparable from one period of life to another regardless
of the form of the distribution. We shall return to this question of
equivalent units in distributions of unlike symmetry when we compare the
definitions of the borderlines of deficiency in terms of intelligence
quotient, coefficient of intelligence, standard deviation and
percentage. Corresponding percentages of corresponding groups have a
more useful definite significance of equivalence than any other units of
measurement of mental ability available when the forms of distribution
vary at different stages of development or are uncertain, as seems to be
true with tested abilities.


When we endeavor to make our ideas of mental development more definite,
we are assisted by thinking of the various stages in graphic form. This
is especially true when trying to think of the position of the deficient
individuals, relative to the average individuals and to genius.

In diagrammatically presenting these concepts in Fig. 3 and Fig. 5 we do
not wish to assume that all the principles on which the developmental
curves have been plotted have been decided. If they make clearer the
points still under discussion and direct the discussion to specific
features so that more data may be brought to bear upon the empirical
determination of their characteristics, they will serve a useful
purpose. For our present ends, we shall consider only certain features
which have a bearing upon the interpretation of developmental scales and
the quantitative definition of the borderline.

In the graphic presentation of the curves of development in Figures 3
and 5 the relative position at various ages has been suggested
hypothetically for those of the best ability and median, or middle
ability, as well as the borderline of the deficients.

It is evident that these graphs should represent equivalent ability at
each stage of development measured by as objective a scale of
measurement as possible. In the graphs this scale is assumed to be
composed of physical units with its zero at zero ability. The deficient
group is distinguished by the portion with a grated shading. The
distribution curves of individual ability we have already mentioned in
connection with scales of measurement. Fig. 3 is constructed on the
assumption of a normal distribution of ability at each age extending to
the same zero ability. Fig. 5 on the assumption of distributions of
varying form.

Otis has given a very able logical analysis of certain concepts
underlying the testing of mental development (_163_). His discussion
differs from the present in its aim to determine the proper mental age
for particular tests, a question which I have not considered. It also
supplements the present discussion by showing the changing value of the
same intelligence quotient with normal distributions of ability under
certain assumptions as to range of ability and decrease in the annual
increments of ability with age.


Some investigators are apparently inclined to question the significance
of any curve of mental development on account of the very different
forms of development which they have found in particular cases. A
quotation from Goddard will state this problem:

  “It seems to me that there is considerable evidence that there are a
  good many children that develop at a normal rate up to a certain age
  and then slow down; some slowing down gradually and others rapidly.
  This is possibly accounted for by accidental conditions. Dr. Healy's
  case of traumatic feeble-mindedness is a good illustration of this.
  We have quite a good many cases, not a large percentage as yet,
  where it is pretty clear that they have developed very nearly
  normally up to the age of seven, eight or nine, so that I am very
  skeptical as to the possibility of formulating a rule for
  determining the rate of development. Many cases are uniform in
  slowness while others vary a great deal; some slow up more rapidly
  than others as has already been stated....

  “Morons are not usually discovered until twelve or fourteen years of
  age. The picture to me of the development of the feeble-minded is
  rather that these different types develop each in his own way very
  much as the physical side develops. Different families have
  different determiners of development. Just as it was determined
  before I was born that I should be five feet, ten inches tall, I
  developed that height and no further. In the same way, probably,
  that determiner carries with it the determination of the rate of
  development and the time. This carries with it the fact that I
  should have been an average boy from birth. As a matter of fact I
  was very much under-size until I was fifteen or sixteen years of
  age. Then I shot up. Other cases are over-size. It may be a false
  analogy, but it seems to me to illustrate the rate at which these
  cases develop” (_111_).

This view raises clearly the question how far the curve of average
development represents a common tendency of different individuals in
development. Are the individual curves of development so varied in form
that an average curve does nothing but obscure their significance? The
study of individual curves of growth in height and weight by Baldwin
indicates that the bigger children tend to develop earlier, the smaller
later (_73_). The individual curves of mental development may be
analogous. If so, the average curves may not adequately represent the
common tendencies of development. Nevertheless, it is to be remembered
that with height and weight the average curves do retain a decided
usefulness, which nobody, I suppose, would seriously question.

An analogous problem arises when we consider the question of variations
in the maturity of different mental processes. Besides the question
whether the average curve is useful in view of the variation among
individuals in their rates of maturity for the same process, the
psychologists have a still more difficult problem about curves of
general ability. These curves are built by combining the results of
numerous psycho-physical tests which are very different in type. We need
to raise the question whether the type of process measured by memory for
digits, for example, matures at the same rate as those processes
measured by other memory tests: in general, how much a single test or
combination of tests represents a common process. Furthermore, we need
to inquire whether processes measured by memory tests mature like those
measured by tests emphasizing reasoning, imagination, motor ability and
other groups of activities. We thus have the problems of the different
rates of maturity of the different tested processes in the same
individual and of common tendencies among these specific processes.

In order more clearly to present this problem of the significance of
developmental curves for different processes, I have brought together
the age norms from 8 to 14 years for 40 tests as given by different
investigators. No norms were included which were not based on tests of
at least 25 individuals. After 14 years the data which have been
collected are open to the objection that the norms for the older ages
would be seriously affected by the fact that they were obtained upon
children remaining in school, usually in the elementary school, _i. e._,
upon groups, among which a large portion of those of better or of poorer
ability had been eliminated. The relative position of the norms for
older ages are, therefore, not comparable with those of children who are
of the ages of compulsory attendance. The results published are
inadequate below 8 years for most of the tests, so I have not extended
the curves to earlier ages. In 14 instances the data for boys and girls
were only given separately. In these I have used the norms for the boys.
A prepubertal break in a combined curve may, therefore, indicate a sex
difference. In most cases the norms were given for the sexes combined,
and the difference is unimportant for the points considered.

The variation in age norms with different tests is shown graphically in
Figures 6, 7 and 8. In order that the various tests may be plotted on
the same scale, so as to compare changes in development for the
different tested processes, I have used the average increase in ability
from 8 to 9 years of age for each test as a common measure and
arbitrarily plotted the slant of the curve between these ages at 45
degrees. The increase from 8 to 9 is represented by 10 units on the
objective scale to the left of the graphs. On this basis it is possible
roughly to compare changes in the absolute annual increase at different
ages for the same test and for different tests. It assumes that the
units in which each test is scored are equivalent for that test. An
average difference between the basal ages or between any two ages cannot
be assumed to be accompanied by the same distribution of increases.
Moreover, the 8-year norm is at different distances from zero for the
different tests so that the relative increase from 8 to 9 cannot be
regarded alike for the different tests. The method, however, is
sufficiently accurate for illustrating the very different forms of the
developmental curves which might be expected if they were measured by
absolute increases from year to year. Even the variation in the slant of
the lines at the different ages gives a graphic picture which will
assist in interpreting the significance of average curves of general
ability. As the curves stand, they show the norms for each age for any
test, as if placed on its own objective scale, and the various objective
scales have been harmonized on the assumption that the norms at 8 and 9
years are accurate. We thus have a simple representation of the absolute
changes in the abilities tested from age to age by the same tests
relative to a single objective scale. It will not give a seriously
erroneous picture for any tested ability so long as the units in which
the particular test is scored may be presumed to be objectively equal.

  The tests on which Figures 6, 7, and 8 were based included
  practically all which were reported in the researches used. They
  were as follows: Norsworthy (_159_), perception of 100-gram
  weight, cancelling A's (boys), ideas remembered from four simple
  sentences, memory of related and of unrelated words, part-wholes,
  genus-species, opposites and reverse of opposites given the next
  day, “a-t” test. J. Allen Gilbert (_108_), taps in 5 seconds,
  fatigue in tapping, visual reaction time, color-discrimination
  reaction time, reproduction of 2-second interval. Smedley (_51_,
  No. 3), strength of right-hand grip (boys), taps in 30 seconds
  (boys), ergograph; visual, auditory, audio-visual, and
  audio-visual-articulatory memory for digits. W. H. Pyle, Standards
  of Mental Efficiency (J. of Educ. Psychol., 1913, IV., 61-70),
  uncontrolled association, opposites, part-wholes, genus-species,
  digit-symbol and symbol-digit substitution, memory for concrete
  and for abstract words, memory of Marble Statue selection, (only
  boys' norms used for each). Pyle and Anderson combined by Whipple
  (_220_) two word-building tests (boys). Anderson as given by
  Whipple memory for letter squares. D. F. Carpenter, Mental Age
  Tests (J. of Educ. Psychol., 1913, IV., 538-544), substitution of
  colors in forms and of numbers in forms, perception time in
  marking A's, concentration, _i. e._, difference in time of last
  test under distraction, memory of pictures of objects, all tests
  devised by Carrie R. Squire. Stenquist (_54_), construction test.
  Sylvester (_191_), form-board test.

[Illustration: FIG. 6. _Tests of the Development of Memory Processes.
Medians at Each Age of the Central Tendencies of the Tests._]

[Illustration: FIG. 7. _Different Types of Development. Medians at
Each Age of the Central Tendencies of the Tests._]

[Illustration: FIG. 8. _Forty Curves of Development. Distribution at
Each Age of the Central Tendencies of the Tests._]

  In Fig. 6 curves A and B are Smedley's tests; curve C includes in
  addition Norsworthy's unrelated words, Pyle's memory for concrete
  and abstract terms, Anderson's letter-squares, Carpenter's memory
  for pictures, and Gilbert's for the time interval; curve E includes
  Pyle's two and Carpenter's two substitution tests; curve F includes
  Pyle's Marble Statue and Norsworthy's memory for related words and
  for sentences; curve S is Norsworthy's; curve D is the combination
  of these 17 tests.

  In Fig. 7 curve H includes Gilbert's visual reaction time,
  Norsworthy's A and a-t tests, Carpenter's two A tests; curve I
  includes Gilbert's and Smedley's tapping tests; curve J is the
  median of the central tendencies of all 40 tests; curve K includes
  Norsworthy's two opposites and her part-whole and genus-species
  tests, the Pyle opposites, genus-species and part-whole tests; curve
  L is the same as D, curve M includes Smedley's strength of grip and
  ergograph tests and Gilbert's fatigue of tapping; curve N includes
  Pyle and Anderson's word building tests and Pyle's uncontrolled word
  association test.

  In Fig. 8 curve P is Gilbert's visual reaction time test, curve S is
  Norsworthy's test for memory of unrelated words, the other curves
  are the median and quartiles for the central tendencies of all 40
  tests after each was expressed at each age in terms of the gain from
  8 to 9 years taken as a unit.

Several points are to be noted about the nature of the curves for
different tests. In Fig. 6 showing the curves for different forms of
memory tests, that for the memory of digits is very different in
character from that for memory of related material. The most extreme
differences in the time of maturity are shown by the test for memory for
digits presented orally and the substitution of color in forms, the
former continues to increase so rapidly relative to the absolute
increase from 8 to 9 years that it cannot be represented in the graph
reaching 539 units of the scale by 14 years of age, while improvement in
ability in the latter is not measured after 9 years. We cannot take time
to discuss how much of the differences between the various curves may be
due to the nature of the tests themselves, the form of scoring the
results, or the condition under which they were given, selection of
subjects, etc. The conclusion is safe, however, that when groups of
three or four tests of similar type show such marked differences as
those for memory of digits and memory for related material we may expect
similar differences in the rates of maturity of the corresponding

From Fig. 7 we may learn that tests emphasizing functions such as speed
of motor or perceptual motor reaction, curves H and I, are notably
different in their form from curves for tests of imaginative processes,
curve N. As we group tests together covering larger ranges of activity
we approach the median curve for general ability. Note the median curve
for 17 memory tests (curve L) compared with the median for the 40 tests
(curve J). By empirical studies we might pick out types of tests which
would most closely represent the maturity of average ability. For
example, the median for the substitution tests, curve E, resembles the
median for the memory tests, curve D, more closely than does that of the
4 digit tests, curve B. Curve K, for 7 association tests, resembles the
median for the 40 tests, curve J, much more closely than the curve for
the perceptual-motor speed tests, curve H. This difference can not be
explained by the use of 7 instead of 5 tests in calculating the central
tendency of the group. It probably means that the sort of
psycho-physical processes usually tested more closely represent on the
average the abilities shown in association tests than they do the
abilities shown by speed of motor reaction. The significance of this
sort of analysis for those constructing a scale for measuring
intellectual ability is obvious.

Fig. 8 shows the median and quartile range for the central tendencies of
the 40 tests and gives examples of two extremely different tests, visual
reaction time and memory for unrelated words. How closely these
particular tests represent fundamental differences in the maturity of
different processes, we cannot, of course, be sure without prolonged
research; but nobody would question that analogous differences would be
found in different processes. When we think of curves of general ability
we must, therefore, keep in mind the light which might be thrown on them
by an analysis of the various processes tested in the particular scale

Another feature of all developmental curves which is apparent as soon as
the causes of development are considered, is that growth in an
individual is the result of several factors. These include the native
capacity, the rate at which that capacity manifests itself
instinctively, and the external stimuli which encourage or retard that
manifestation. To some extent these factors vary independently. Our
curves of development will never completely express all the facts until
they analyse out all these factors for each of the processes. In the
meantime we shall be able to think of general trends of development by
considering average curves. The fact that they represent combinations of
unanalyzed factors must, however, make us very cautious in interpreting
our norms.


There has been considerable discussion of the form of the curves of
mental development. The logical aspects of the curves on the assumption
of normal distribution of ability at each age and uniform age of
maturity have been treated by Otis (_163_) and the bearing of these
assumptions upon the Binet scale pointed out. Thorndike has plotted the
developmental curves for a dozen tests on the basis of the variability
at 12 years of age used as unit and gives a chapter in his Educational
Psychology to the changes with maturity (_198_, Chap. XI). Bobertag
suggests that the rates of development of normal and deficient children
are analogous to the upward progress of two projectiles fired from such
different heights that the force of gravity would retard the lower
projectile more than the upper (_81_). This analogy supposes that the
rate of maturity would continually decrease and that those who were
feebler mentally would be arrested in their developmental earlier.
Bobertag, Kuhlmann (_137_, _138_) and Otis give evidence from the
results of Binet testing that the rate of development decreases with
age. The percentages of older children passing certain positions on the
Binet scale or certain tests taken from it were found to change less at
year intervals for the older ages. This evidence is not conclusive
unless we know that the positions compared are at the same point in the
distributions of ability at the beginning of the periods of growth. The
same percentage change at a point farther away from the central tendency
would mean a larger growth than at the middle of the distribution, when
judged either in reference to a physical scale or to units of deviation.

While recognizing that the complete curve of mental development is
logarithmic in form Pearson contends that, when measured by Jaederholm's
adaptation of the Binet scale, development is adequately represented by
a straight line from 6 to 15 years of age (_164_). As this conclusion is
based upon the use, as equivalent units, of years of excess and
deficiency at all these ages the data lacks the cogency of a scale of
equal physical units.

With the Point Scale it is not known whether the units in different
parts of the scale are equivalent. Without assuming that they are equal
it is impossible to discover the form of curves of development from the
records of children at a series of ages. Yerkes and Wood publish a curve
of the increase of intellectual ability based upon point-scale
measurements, which resembles in form the hypothetical curves. They say:

  “The point-scale method has the merit of indicating directly the
  rate, or annual increments of intellectual growth. We do not claim
  for our measurements a high degree of accuracy, especially in the
  case of the early years of childhood. But even the roughly
  determined curve of intellectual growth from four to eighteen years,
  which we present below, has considerable interest for the genetic
  psychologist and for the psychological examiner. We have ascertained
  that whether measured by the ratio of the increment of increase,
  year by year, to the norm for the appropriate year or by the ratio
  of the extreme range of scores to appropriate year norms,
  intellectual development rapidly diminishes in rate, at least from
  the fifth year onward” (_169_, p. 603).

Waiving the question whether annual increases or the range of
measurements relative to the age norms would be satisfactory indications
of the change in the rate of growth, it seems to be fairly clear that
neither of these criteria would be adequate unless we first knew that
the units in which they were measured were equivalent at different
portions of the scale. To show that the point scale units are even
theoretically equivalent it would seem to be necessary to assume, on the
basis of normal distribution of ability, that each unit of the deviation
for each age distribution either equaled the same number of scale units
or the same proportion of the total distance from lowest to highest
ability at each age measured in the point-scale units. The originators
of the scale do not seem to have planned it with this in view. Moreover,
the difficulty of empirically demonstrating such equivalence of units on
a point scale or any form of the Binet scale prevents its use for
indicating curves of mental development, however serviceable it may be
for other purposes.

The simplest demonstration of the form of the development curves is
applying the same test, scored in equal physical units, to children of
different ages. In Figs. 6, 7, and 8 the evidence from tests was
assembled for ages 8 to 14 inclusive. It is probable, however, that the
form of these development curves, when the unit of measurement was
anything but time taken for the same task, has been affected by the
difference in the real value of units called by the same name, _e. g._,
giving the opposite of one word is not always equal to giving the
opposite of another.

The best developmental curves empirically determined are probably those
for the form board presented by Sylvester (_191_), Wallin (_212_) and
Young (_227_) since in each of these cases the same test was presented
at all ages and the scores were in equal physical units of seconds. It
can hardly be supposed, however, that the form board curves alone would
be typical of average mental development. To know something about the
general curve of mental development we need a combination of a number of
mental tests scored on scales of equal units. These may be either equal
physical units or units on scales for mental development similar to
those of Thorndike and others for measuring educational products,
handwriting, arithmetic, spelling, _etc._

That either a straight line or a simple curve would represent the
development of ability from birth to maturity is very doubtful. When we
consider the entire developmental curve from birth nobody doubts that
there is a change in the rate of development at the time of the arrest
of instinctive changes at adolescence. There are probably fluctuations
in the rate before this final arrest. Pintner and Paterson also assume a
complex curve of development (_44_). Whether the fluctuations should be
allowed for in the description of the borderline of deficiency is the
important question in our study. With measurements of bodily growth we
noted that changes in the rate of maturity are accompanied by a skewness
of distribution of ability at the ages affected. The same effect may be
expected with mental measurements. The percentage method of defining the
borderline of deficiency has an advantage when the form of distribution
at any age is uncertain (See Chap. XIV, d.). Since the changes in the
rate of development are most likely to be important at the prepubertal
and adolescent ages the description of the borderline in terms of
deviation or quotient may be expected to be most uncertain at this
period. Moreover, none of the quantitative definitions of the
borderline, except the percentage method, remain equivalent if rates of
development of normal and deficient children change relative to each
other, a question we shall now consider.


It has been assumed by Bobertag (_81_), Stern (_88_), Goddard (_117_)
and others that deficient children reach their maturity earlier than
normal children. If this were true the curves of mental development for
the average and for the deficient children should not be expected to
retain their same relative positions after the idiots had begun to show
arrested development. Moreover, unless this arrest were compensated by
some peculiar form of accelerated growth among those above normal
ability, we might expect that the distributions of ability would change
in form at the various ages after arrest had begun. A relative increase
in the distance of older deficients from the average as compared with
younger deficients may be interpreted as meaning either the earlier
cessation of growth of the deficients or a change in the relative rates
of growth of individuals of different mental capacity. When fully
considered the present evidence from the Binet tests fails, I believe,
to demonstrate the earlier arrest of the deficients, although it is
undoubtedly true that the Binet scale may not be fine enough to measure
the improvement of idiots. We shall take up certain investigations that
bear upon this point.

Goddard has reported tests upon the same group of 346 inmates in an
institution for the feeble-minded who were tested three years in
succession (_117_). The paper suggests that the idiots, as a group
increased less in absolute ability than those of higher mental age. The
average gain for 55 idiots who tested I or II mentally was about half a
test in the two years. In order to reach our present problem, however,
we must know that the idiots, for example, developed relatively less
mentally than did those of the higher grades of ability in the imbecile
and moron groups of _the same life-ages_. This question cannot be
answered from the paper. It probably cannot be adequately answered from
mental age results on account of the irregularity in the value of the
year units at different points on the Binet scales.

Bobertag summarizes Chotzen's data obtained by the examination of the
children in the Breslau Hilfsschulen with the Binet scale. He believes
that the position on an objective scale attained by the average of these
retarded children is progressively lower with advancing age relative to
the average position attained by normal children, assuming that the
quotient for normal children remained constant at each age. The average
intelligence quotients of all the children in the special schools
(exclusive of those testing III or less) was 0.79 for those 8 years of
age, 0.72 for those 9 years, 0.70 at 10, and 0.67 at 11-12 (_81_, p.

Stern also compiled a table from Chotzen's results which shows this
decrease in intelligence quotients with life-age separately for each
group of those whom Chotzen by his expert diagnosis regarded as
imbeciles, morons, doubtful, and not feeble-minded although attending
the special schools (_188_, p. 80). This table is reproduced here as
Table XX. On the surface it suggests that the quotients of the extreme
groups are nearer together at the older ages, instead of being farther
apart. The objection to this evidence from the Binet scale is that the
norms are not equivalent for different ages on the scale used. Since the
objective norms on the Binet scale are more difficult to attain at the
older ages this variation would tend to make older children show lower
quotients than the same children would show at younger ages, so that
such tables are quite uncertain in significance.

                               TABLE XX.

                       Chotzen's Tables X & XI.)

   LIFE-AGE   │     NOT      │   DOUBTFUL   │   MORONS    │  IMBECILES
              │FEEBLE-MINDED │    DEFECT    │             │
       8      │     0.92     │     0.84     │    0.76     │    0.71
       9      │     0.85     │     0.81     │    0.77     │    0.67
      10      │    (0.80)    │    (0.80)    │    0.74     │    0.62
      11      │    (0.73)    │    (0.68)    │    0.71     │   (0.64)
      12      │    (0.75)    │    (0.75)    │   (0.73)    │   (0.61)
      13      │              │    (0.73)    │             │

The Jaederholm data with his form of the Binet scale, as treated by
Pearson, shows a straight regression line for the backward children
which falls below the normal development line on the average four months
of mental age for each additional year of life from 7-14 (_167_).
Accepting Pearson's interpretation that a year of excess or deficiency
and a year of growth is a constant unit, we find that the deficient
group from special classes was falling continually behind the normals
with increase of age a relatively greater distance from any rational
reference point. Pearson accounts for this change in the distance
between the two groups of normal and backward children, as I understand
his paper, by supposing that with increase in age more and more normal
children become deficient. It would seem that this data would be more
easily explained by supposing that the distributions became skewed
toward deficiency for the older ages, rather than that the distributions
remained normal and became flatter.

The best evidence as to the relative positions of the curves for
deficients and those for average ability would be provided by using
psychological tests that could be adequately scored in terms of equal
physical units for the same task. The position of various lower
percentiles relative to the average or to an assumed reference point
could then be compared on the same objective scale. I have reviewed
studies of this type in discussing skewed distributions in Chap. XIII,
A, c. I there reached the conclusion that the weight of the evidence was
that the distributions were slightly skewed in the direction of
deficiency, although the evidence was not conclusive. We are now raising
the further question whether this skewness increases with age.

On account of the difficulty of determining the points for zero ability
in terms of the physical scales used, let us see what conclusion might
be reached if we calculated the relative distance of median and low
ability of equivalent degree from the scores of the same higher degree
of ability assumed as a reference point at the various ages. There seems
to be no reason in the theory of measurement why the highest score
instead of the lowest score in random samples might not be used for a
reference point for comparing the distances between normal and deficient
children at different ages. Instead of using the highest single score,
it would be better to use the upper quartile or quintile since it would
be less affected by a chance error in giving the test.

Applying this method to determining the relative position of median and
retarded ability I have calculated the data for the form board test
cited previously from Sylvester (_191_) and from Young (_227_). This
affords the only adequate evidence of which I know, derived from tests
scored in equal physical units given to sufficiently large groups to
indicate whether or not the retarded group changes its relative position
from the normal group at different ages. The comparison is shown in Fig.
9. With Sylvester's data the distance of the lower quartile in ability
from the median is compared with the distance of the upper quartile from
the median, the latter distance being taken as a unit. With Young's data
for Witmer's form board the quintile is used instead of the quartile and
each sex is given separately. Since Young's table shows the scores for
half ages, it was necessary to take the average of the two scores, thus
giving the approximate score for the middle of the complete age group.
The graph discloses no pronounced tendency for the retarded group to
fall relatively farther behind the median with increase in age. There
are, however, notable fluctuations in the relative positions of the
groups so that at 7 years with Young's data for boys and at 13 years for
Sylvester's curve the retarded group is twice as far from the median
relative to the distance between the median and the corresponding better
group as it is at some other times. It is possible that the curves for
the older groups of those of poorer ability are too high since it is
likely that more of the actually deficient children tend to be dropped
from the public school classes with increase in age. Nevertheless, so
far as the evidence at present goes it is not sufficient to determine
whether the backward and the corresponding better group show a general
change in their relative distances from the median with approach to

[Illustration: FIG. 9. _Relative Positions at Each Age of the Median and
of Corresponding Bright and Retarded Children with the Form Board

On the other hand the curves indicate the tendency for the distributions
to be skewed toward deficiency and for the relative distances to
fluctuate as we should expect if the accelerations in growth occurred at
different ages for those of different ability. The data of Young suggest
that there may be sex differences in the age of acceleration, the
backward girls showing accelerations, relative to the upper group at
ages 7 and 12, a year or more before the boys. For Sylvester's data the
ratio of the distance between the median and the lower quartile divided
by the distance between the median and the upper quartile for each of
the age groups is as follows: 5 yrs. 1.8, 6 yrs. 2.4, 7 yrs. 3.0, 8 yrs.
2.0, 9 yrs. 2.2, 10 yrs. 2.4, 11 yrs. 2.0, 12 yrs. 1.8, 13 yrs. 3.0, 14
yrs. 2.1. For Young's data the corresponding ratios are—Boys: 6 yrs.
1.5, 7 yrs. 1.9, 8 yrs. 1.5, 9 yrs. 0.8, 10 yrs. 1.6, 11 yrs. 1.2, 12
yrs. 1.4, 13 yrs. 1.0, 14 yrs. 1.3. Girls: 6 yrs. 1.7, 7 yrs. 1.0, 8
yrs. 1.5, 9 yrs. 0.9, 10 yrs. 1.0, 11 yrs. 1.3, 12 yrs. 0.9, 13 yrs.
1.5, 14 yrs. 1.4. Changes in the rate of growth causing asymmetrical
distributions are to be expected throughout the periods of growth. A
fundamental skewness toward deficient mental capacity, therefore, would
be indicated only if it were found at maturity or at ages when the
average rate is decreasing, when the more capable individuals would
theoretically approach relatively nearer the deficients if the latter
accelerated later.

So far as physical growth is concerned Baldwin (_74_, _75_) has shown
with repeated annual measurements on the same group of children that the
period of adolescent acceleration shifts from 12½ years for the tallest
boy to 16 years for the shortest boy. For the tallest girl the maximum
height was attained at 14½, for the shortest at 17 years, 3 months.
Maturity may be reached at 11 years by a tall well nourished girl, while
with a short girl light in weight it may be delayed until 16. “Children
above medium height between the chronological ages of 6-18 grow in
stature and in physiological maturity in advance of those below the
medium height, and they may be physiologically from one to four or five
years older than those below the medium height. Those above the medium
height have their characteristic pubescent changes and accelerations
earlier than those below; there is a relative shifting of the
accelerated period according to the individuals' relative heights”

Doll presents evidence from the physical measurements of a large
feeble-minded group in institutions which he suggests shows that the
shorter among them cease growing earlier. When the height of these
feeble-minded is measured in relation to the Smedley percentiles of the
height of normal children of their corresponding ages, he finds a
correlation of -.20 between age and percentiles of height, the taller
relative to normals being younger. He says: “This confirms Goddard's
similar conclusion, but negatives for the feeble-minded at least, the
theory affirmed by some writers, that children who grow at a retarded
rate continue their growth to a later age” (_98_ p. 51). On the contrary
this minus correlation is more likely to mean only that the Smedley
norms on school children are too high for the older ages because of the
excess of taller children who remain for the high school work. This
would give the minus correlation without supposing that the taller
individuals continue their growth to a later age, as he thinks.

Moreover, a total longer period of physical growth for smaller, less
normal, children has been demonstrated. Boas (_80_) says: “Among the
poor the period of diminishing growth which precedes adolescence is
lengthened and the acceleration of adolescence sets in later; therefore,
the whole period of growth is lengthened but the total amount of growth
during the larger period is less than during the shorter period of the
well-to-do” (_80_). A reversal in growth tendency between brain capacity
and size of body, which is supposed when the mentally deficient are said
to arrest earlier, would be one of the most puzzling paradoxes in the
study of development. We should, therefore, be exceedingly cautious
before accepting the hypothesis of the earlier maturity of deficient

A complicated situation is presented when we come to represent
graphically the effect on the distributions of these differences in
growth among those of different intellectual capacity. In the
hypothetical diagrams, Fig. 5, it is shown how arrest of development
might be presented graphically in relation to the distribution curves,
ability being measured on the same physical scale. The earlier
acceleration and earlier maturity of those of better ability are
indicated. The distributions are shown as skewed at all ages after
birth. Equivalent units of mental development at different ages can be
found only in corresponding percentages of the groups, not in the units
of the deviation or in development quotients relative to the averages at
different ages. In other words the lowest 0.5% continues to be an
equivalent unit while -3 S. D. measures different portions of the group
and different portions of the distance from lowest to highest ability.
Corresponding percentages retain one common significance, namely, that
the same proportion of the group is ahead in the struggle for survival,
regardless of the form of the distribution.

It is hoped that the discussion of the statistical problems connected
with the quantitative study of mental development has given more meaning
to the different attempts to devise scales for measuring mental ability.
It should be noted that the same relative development at different ages,
expressed relative to the distance from lowest to highest ability
measured in equal objective units, does not correspond to the same
relative development measured in percentages of the groups, as soon as
the forms of the distributions change. The theoretical considerations
show that we have available at once a perfectly definite and clear
method of stating relative development in terms of corresponding
percentages of corresponding groups. If the groups distribute normally
these units are translatable into units of the standard deviation of the
group. If the distributions change in symmetry the only equivalent units
of deficiency available are in terms of corresponding percentages
reading from either end of the group. On the other hand percentile units
are not equivalent in _amount_ of change for the same distribution, so
they are of most importance for comparing different age distributions of
uncertain forms.

Until we have a scale of equal objective units for mental ability, it is
not possible to obtain a measure of relative development which shall
take into account the _amount_ of relative change. We must be content to
measure the change in percentile rank (changes in serial position) of an
individual relative to those of his own age.

Having clarified our conceptions of mental development and brought them
into harmony with certain suppositions regarding the distribution of
ability and its change from year to year, we are in a better position to
evaluate in the following chapter the different objective methods of
defining the borderline of feeble-mindedness.


On the basis of the detailed conception of the developmental curves and
distributions of ability at different ages, which we have been
considering, we can now compare the percentage method with other
quantitative methods of describing the borderline on developmental test


The earliest form of the quantitative description of the borderline on a
scale of tests, was in terms of a fixed unit of years of retardation.
This was taken over apparently from the rough method of selecting school
children to be examined for segregation in special classes by choosing
those who were two or three grades behind the common position for
children of their ages. As this amount of school retardation was greater
for older children, an additional year of retardation was required after
the child had reached 9 years of age. I believe that nobody would
seriously defend a practice of making an abrupt turning point of this
kind, except on grounds of practical convenience. The theory of stating
the borderline in terms of a fixed absolute unit of retardation is so
crude that it has now been generally superseded by methods which make
the amount of retardation a function of the age.

In order to relate the definition to the age of the child, at least
during the period of growth, Stern suggested the “intelligence
quotient,” consisting of the tested age divided by the life-age (_188_).
This has been adopted by Kuhlmann with his revision of the Binet scale
(_139_) and by Terman with the new Stanford scale (_197_). With the
Point scale Yerkes utilized a similar ratio method for stating
borderlines by what he calls a “coefficient of intelligence.” He defines
it as “the ratio of an individual's point-scale score to the expected
score, or norm” (_226_, p. 595). Haines also uses these coefficients,
dividing the individual's score on the Point scale by the average number
of points scored by those of his age (_26_). The difference between the
“quotient” and the “coefficient” seems to be mainly empirical since they
are theoretically alike in principle provided the scales by which they
are determined are composed of equal units. Empirically, however, the
units of the point scale would have to be compared with the 0.1 year
units of the Binet scale to determine which showed the greater
uniformity within its own scale. The coefficient has an advantage over
the quotient in that the scale norms for the different ages would
automatically become readjusted with additional data, and that
physiological age norms could be more readily stated if they were ever

The suggestion of defining the borderline of tested deficiency in terms
of a multiple of the standard deviation of ability of children who are
efficient in school was made by Pearson in 1914. Tested inefficients did
not with him include all inefficients, as he recognized other sources of
deficiency. He had previously suggested a scale of mental ability in
units called “mentaces”, 100 of which were equivalent to a unit of the
standard deviation of all ability assumed to be normally distributed. On
this scale of mentaces the imbeciles were 300 mentaces or more below
average ability and would be expected to occur once among 1000
individuals chosen at random. Very dull, including some mentally
defective individuals, were also to be found from 208 to 300 mentaces
below the average (_166_, p. 109). Defining the borderline in terms of
the deviation of a normal population was definitely forecasted by
Norsworthy, although she did not specifically discuss the problem of the
borderline. She indicated that if children tested below -5 P.E., they
might be regarded as outside the normal group.

The following quotation from Pearson will make the method of stating the
borderline in terms of a multiple of the deviation clearer:

  “Now the question is, what we mean by a 'special or differentiated
  race': I should define it to mean that we could not obtain it by any
  selection from the large mass of the normal material. Now in the
  case of the mentally defective, we could easily obtain children of
  their height, weight, and temperature among the normals. We could,
  out of 50,000 normal children, obtain children practically with the
  same powers of perception and memory as the feeble-minded, as judged
  by Norsworthy's data. But not out of 50,000, nor out of 100,000
  normal children, could we obtain children with the same defect of
  intelligence as some 50% of the feeble-minded children. In other
  words, when the deviation of a so-called feeble-minded child from
  the average intelligence of a normal-minded child is six times the
  quartile or probable deviation of the group of normal children of
  the same age, it falls practically outside the risk of being an
  extreme variation of the normal population. Now six times the
  quartile variation is almost exactly four times the standard
  deviation or the variability in intelligence of the normal child,
  and in the next material I am going to discuss [Jaederholm's], we
  have shown that the standard deviation in intelligence of the normal
  child is just about one year of mental growth” (_164_, p. 35).

With the Jaederholm data obtained in testing children in the regular and
in the special classes in Stockholm by a modified form of the Binet
scale, Pearson found that a year of excess or defect in intelligence was
practically a uniform unit from 7 to 12 years of age and was about
equivalent to the standard deviation of normal children measured in
these year units. He, therefore, uses a year unit and the standard
deviation as interchangeable for these data. He does not, however,
always make it clear whether he means that the equivalence of the year
units is determined by the standard deviation of the children of all
these ages grouped together in one distribution, as it is in determining
the regression lines, or by the equivalence of the standard deviations
of the separate ages, especially when these two deviations are not equal
in terms of the year units on the scale. I shall assume, however, that
he would use the deviations of the separate years in case of such an
inequality of the two concepts.

The quotation from Pearson, which we have given above, indicates that he
would determine the borderline on the scale by the standard deviation of
'normal' children. In his case he actually used children who were
efficient in school, as contrasted with those in special classes. On the
other hand, he argues at length that all mental ability, including that
of the social inefficients, is distributed in the form of the normal
curve (_167_). Under this assumption it is, therefore, little
theoretical change in his position to suppose that the borderline might
be described in terms of the standard deviation of a random sample of
the population. Defining the borderline in terms of a multiple of the
deviation of a random sample at each age thus becomes directly
comparable with the other forms of the quantitative definition,
supposing that all refer to conditions to be found in a completely
random sample. It is in this sense that I shall refer to the method of
defining the borderline in terms of a multiple of the deviation.

The percentage method of defining the borderline seems to have been the
spontaneous natural working out of the problem in the minds of several
investigators. At the same time that I suggested this method in a paper
before the American Psychological Association (_151_) Pintner and
Paterson had prepared a paper suggesting a percentage definition of
feeble-mindedness (_44_) and Terman had worked out his use of the
quotient so that the borderline in terms of the quotient was given
equivalent form in terms of percentage. Nobody, however, seems to have
attempted to work out the details of the method as in the present

  As a point of detail it is to be remembered that in translating
  percentages into terms of the deviation, the size of the group for
  which the percentages are determined is important if the groups are
  small, since the same percentage lies above slightly different
  multiples of the standard deviation with different sized groups. On
  this point the reader may see a paper by Cajori and the references
  cited there (_86_).


In distinction from qualitative methods of describing the mentally
deficient, all quantitative definitions assume that those of deficient
mentality do not represent a different species of mind; but that they
are only the extreme representatives of a condition of mental ability
which grades up gradually to medium ability. The deficient are not an
anomalous group such as we find with some mental diseases. Except for
the comparatively rare cases of traumatic or febrile origin, the
deficient individual is a healthy individual so far as his nervous
system is concerned, even though his capacity for brain activity is
below that of those who socially survive. They are not as a group
abnormal in the sense of diseased, but only unusual in the sense of
being extreme variations from medium ability in a distribution which is
uninterrupted in continuity. This distinction has been fully discussed
by Goring in his work on _The English Convict_, which those who are
interested in a full mathematical discussion of the significance of
mental deficiency are urged to read.

  Schmidt urges that the deficients are qualitatively different in
  being “unable to plan”, and then suggests tests which most markedly
  bring out this distinction between deficient and normal children
  (_178_). As I have said before, however, this seems rather to be a
  failure to recognize that such an attempt to find tests which
  “qualitatively” distinguish the two groups is only an effort to pick
  those tests which best make measurable the differences between
  individuals at the extreme of mental ability. As such it is a
  valuable contribution to this problem. If it is intended as an
  attempt to set up a qualitative distinction in a mathematical or
  biological sense, between deficient and passable ability, it seems
  to me wholly to fail. As I take it, a “qualitative” distinction with
  Schmidt is only a bigger quantitative distinction and is intended
  only to mean this.

None of those who advocate quantitative definitions would contend, I
believe, as some of their opponents seem to think, that such definitions
afford a final diagnosis for particular cases. In attempting to place
the borderlines on a scale of tests, this is always done with the clear
recognition that such borders are _only symptomatic of deficiency_. The
diagnosis of “social inefficiency,” to use Pearson's term, rests upon
many facts among which the test result is only one, albeit the most

Other characteristics which each of the above quantitative definitions,
except that of a constant absolute amount of deficiency, have in common,
or might easily have if they were stated in their best forms, include
the possibility of adaptation to any developmental scale, the suggestion
of borderlines for both the mature and immature, the distinction of a
group which might be regarded as presumably deficient from one that was
of better but doubtful ability and of this from a still better group
which was presumably socially efficient.

Perhaps the most curious and important thing about these definitions is
that they are all substantially identical, except in their terminology
so long as general mental capacity is found to distribute in the form of
the normal probability curve and to extend to absolute zero ability at
each age. This can easily be seen by comparing the distribution curves
in Fig. 3. The position of the percentage borderline would always
represent the same distance from the average in terms of the standard
deviation of each age and the same ratio when the life-age of arrest of
development had been determined as the largest divisor. Under these
conditions, therefore, these main statements of the quantitative
definition agree in supposing that the same proportion of the
individuals of each life-age would test deficient. Those who advocate
any of these quantitative definitions logically commit themselves to
assuming that the percentage of deficients at each age is practically
constant, unless they suppose the symmetry of distribution varies or
does not extend to the same zero point.

If the distributions do not extend to the same zero points of lowest
ability on an objective scale (see Fig. 5), the ratio is clearly at a
disadvantage compared with either of the other methods, since it assumes
that the same percentage of average ability is an equivalent measure.
This does not hold when the lowest ability at different ages is not at
the same point on the scale of objective units. For example, .7 of an
average 100 units above 0 is not equivalent to .7 of an average 150
points above a zero ability of 30 points on the objective scale. The
idea of regarding percentages of averages as equivalent is therefore
generally avoided in mental measurement. In case the position of the
absolute zero points of ability may be different, the distance from the
average should be stated in terms of the deviation. In this respect the
method of the deviation or the lowest percentage are equally good so
long as the form of distribution does not change.


1. With the percentages fixed at the lowest 0.5% as presumably deficient
and the next 1.0% doubtful, these borderlines for tested deficiency have
the advantage of being more conservative than those at present
advocated. On the basis of our empirical knowledge this is an important
reason for urging borderlines on the scales at least as low as those
suggested herein. Disregarding the extremely high borderlines which have
fallen into disuse, we still find that social deficiency is often
presumed for those testing above the lowest 1%. With the new Stanford
scale, Terman presumes “definite feeble-mindedness” below an
Intelligence Quotient of .70, below which he finds that 1% of 1000
unselected children fell. I Q's from .70 to .80 would include his
uncertain group, which he describes as “border-line deficiency,
sometimes classified as dullness, often as feeble-mindedness” (_57_, p.
79). His tables show 5% below an I Q of .78. We have no results with a
_random_ group of adults by which to judge how many would be below these
borders. When the I Q has been applied to scores with other scales a
larger percentage has often been found to be excluded. Fernald has shown
that Haines' suggestion of a coefficient of .75 with the Point scale
would exclude 16% of 100 Cincinnati girls selected at random from among
those who left school at 14 years to go to work (_16_).

Unless the examiner wishes to assume that social inefficiency is more
frequent than it has been demonstrated by the practical tests of life,
the success of those who have low quotients should make him exceedingly
cautious about accepting the various borderlines which have been
suggested by those who have not tested their criteria by the percentage
method. It is not merely that the borderlines should be lowered, but
that they should be lowered under some consistent plan so that we should
know as much as is possible about their significance in the prediction
of ultimate social inefficiency, and that we should be able to readjust
them on the basis of new data or to new scales.

With the Point scale Yerkes and Wood say regarding “the coefficient of
intelligence .70, which we accept as the upper limit of intellectual
inadequacy or inferiority”: “Our data indicate that grades of
intellectual ability measured by the coefficient .70 or less are
socially burdensome, ineffective, and usually a menace to racial
welfare” (_226_). With the most reliable part of their data, that for
children from 8-13, this coefficient excludes the lowest 8.39%.
Moreover, the lowest group for which they suggest a borderline, the
dependents, falls at .50 or below and includes 1.05%.

2. A second practical advantage of the percentage borderlines on the
scale is that they make no assumption as to the uniformity of the norms
for the different ages. Except for the Stanford and the Jaederholm
scales, there is little evidence that the age norms exclude equivalent
portions of the children at the different life ages.

Goddard's Table I gives the data from which the following percentages of
those who pass the norm are calculated, not counting those above 11
years, since the older groups are clearly affected by selection:—5 yrs.,
88%; 6 yrs., 79%; 7 yrs., 81%; 8 yrs., 51%; 9 yrs., 60%; 10 yrs., 73%;
11 yrs., 44%. Kuhlmann's figures when using his own revised scale with
public school children including the seventh grade, are:—6 yrs., 100%; 7
yrs., 95%; 8 yrs., 90%; 9 yrs., 87%; 10 yrs., 81%; 11 yrs., 80%; 12
yrs., 57%. It is clear that any change in the test norm from age to age
must disturb the quotient which is based on these norms, although it
would not affect the intelligence coefficient with the Point scale.

3. A third advantage of the percentage method arises from the fact that
we cannot presume that the same ratio in terms of the scale units will
exclude the same degrees of ability at different ages even when the
norms for these ages are properly adjusted. The earlier results with the
Stanford revision show a large variation as to the percentage excluded
by the same I Q at different ages. For example, an I Q of .76 would have
shut out 1% of 117 non-selected 6-year-olds, 2% of 113 9-year-olds and
7% of 98 13-year-olds. The lowest 1% of the last group was below a
borderline of .66 (_197_).

With widely varying norms of the other scales, the I Q borderlines show
much greater variation. In a recent review of the evidence, including
Descoudres' report (_96_) on retesting the same children for several
years Stern recognizes that an I Q index is not constant after 12 years
(_187_). Doll records decided changes in quotients for the same
individual at different ages (_99_). So far as the 1908 scale is
concerned, using Goddard's data, our Table V shows that at five years of
age the lowest 1.8% would fall at or below a quotient of .40, at eight
years the lowest 1.9% would show a quotient of .62 or less, and at 15
years the lowest 2.8% fall below a quotient of .75. The rough tentative
approximation of scale limits which I have suggested for the lowest 1.5%
shows that a series of quotients for children from 5 to 15 years of age
would be below .75 at every age and below .65 for half of these ages.
For the presumably deficient group the quotients would be still lower in
order to be as conservative as the borderlines that I have suggested
with the Binet scale as at present standardized.

With the coefficient of intelligence and the Point scale, the Yerkes and
Wood data show that their borderline of .70 excluded 13% of 196 children
8 and 9 years of age, while it excluded only 5% of each of the next two
groups of double ages. With the group of 237 18-year-old Cincinnati
working girls it excluded only 3% (_226_).

The data at present available thus indicate that we should not expect to
find the same ratio at different ages excluding similar percentages. If
the ratios have a value for comparing individuals of different ages,
they seem to fluctuate so decidedly from age to age that they can hardly
be trusted for stating the borderlines of deficiency without empirical
confirmation for each age.

Pearson found that the children of the older ages in the special classes
were more and more deficient, measured in terms of the standard
deviation of the normal group. This shift on the average was four months
of mental age downward for each year of life during the period 7-14
which he studied. It makes uncertain the definition of the borderline in
terms of a constant multiple of the deviation or of a constant quotient,
unless this shift is shown to be due to imperfections of the tests which
can be corrected, or to changes in the selection of the tested groups at
advanced ages.

Pearson's suggestion of -4 S. D. as a borderline with the Jaederholm
data gives some very curious results with the group of children in the
special schools at Stockholm. Under his interpretation at life-ages 8-11
from 0 to 5.2% of the pupils in these classes would be regarded as
deficient, while for life-ages 12-14, 15.2% to 44.4% are beyond -4 S. D.
In passing it is to be noted that if one accepted Pearson's suggestion
that the borderline should be fixed at -4 S. D., in case the
distribution of mental capacity were strictly normal, only four children
in 100,000 would be found deficient, according to the probability

With the method of the standard deviation it would be necessary either
to show that the deviation was constant in terms of the year units or
else to restate the borderline for different ages in terms of the scale
units. The irregularity of the norms with the Binet scale could also be
allowed for, of course, by stating different quotients for the different
ages, but when this readjustment is required for either the ratio or the
deviation in terms of the scale units, these methods lose all their
advantage of simplicity. Instead of one ratio or one multiple of the
years of deviation, we might have a different statement for each
life-age. With the percentage method there would be only one statement
of the borderline for all ages in terms of percentage, although the
scale positions change which shut out the same lowest percentage.

4. All the quotient methods of defining the borderline encounter a
serious practical difficulty in fixing the borderline for the mature, so
that it will be equivalent to that for the immature. With the Stanford
scale in calculating the quotient for adults, no divisor is used over 16
years. Yerkes and Bridges also think that this is about the time that
the development of capacity ceases. Kuhlmann and others use 15 as the
highest divisor. Wallin objects to either of these ages being used as
the age of arrest of mental development (_15_, p. 67). Both the methods
of the standard deviation and percentage have a similar difficulty, in
that the borderline for the mature has to be empirically determined on a
test scale. In this dilemma, however, the data collected with the random
group of 15-year-olds in Minneapolis and published in the present study,
places the borderline for the mature on either the 1908 or 1911 Binet
scale in a much safer position, so far as empirical data is concerned,
than the borderline for the mature for any other scale. This is true
whether that borderline be then stated in terms of either the quotient
or percentage methods. Translated into terms of the quotient, our
percentage borderlines for the mature with these scales, below X for
presumably deficient and below XI for the uncertain, would amount to
quotients .60 and .66 on the basis of our findings with this random
group of children who have presumably about reached adult development.
Pearson does not attempt to define any borderline for the adults on the
basis of the deviation, since Jaederholm tested only children. Moreover,
this is not possible empirically with our group of 15-year-olds, since
we tested only the lower extreme of this group.

Unfortunately, the borderlines of the mature for the Stanford and other
scales depend upon empirical results obtained not with random groups,
but upon a composite of selected groups of adults built up by the
investigator on an estimate that this combined group represents a random
selection among those with a typical advance in development, an almost
superhuman task. Fortunately the empirical determination of this
borderline for the mature might be improved later by obtaining data on
less selected groups. The clearer significance of the empirical data for
the borderline for the mature which I have presented for the Binet 1908
and 1911 scales from a random group of 15-year-olds seems to be an
important practical advantage. It provides an empirical basis for
judging the implication of test results with adults. It gives adults the
benefit of the doubt if they improve after 15 years of age.

5. Compared as to their popular significance, there is no doubt that the
lowest 0.5% of the individuals of a particular age has very much more
significance to those not familiar with detailed statistical practise
than a coefficient or a multiple of the standard deviation. A statement
that an adult has only the tested ability of a child of 7 years is
certainly much more impressive than his score in other quantitative
terms. It will probably always be desirable, therefore, to supplement
any other method of scoring by a statement of the individual's test age.

                       FORM OF THE DISTRIBUTIONS

With our present series of tests, the percentage method will best
provide a concept of the equivalence of the borderlines at different
ages provided the form of the distribution does not remain uniform. I
discussed this question briefly in connection with units of measurement.
In considering curves of development, I assembled some of the evidence
which makes the assumption of normal distribution or even of a constant
skewness at least uncertain. In my opinion the weight of the evidence is
against the hypothesis that the distributions retain a constant form
during the period of development. If this were clearly demonstrated,
both the ratio methods and deviation would fail to express equivalent
borderlines for the different ages with the Binet scales. A fixed
multiple of the standard deviation or a fixed quotient would exclude
different percentages of the population at each age when the skewness
varied. By reference to Figures 3 and 5, it can be seen that, if our
physical units in which we expressed the measurement were uniform and
ability always extended to the same absolute zero point, it is true that
.01 of the physical units reached by the best at each age would be the
same relative amount of ability of the best at each age, stated in
physical units, _regardless of the form of the distributions_. Such a
concept, however, has an unknown biological or social significance so
far as I can see, except for a constant form of distribution. The same
relative physical score compared with the highest at each age,
theoretically might exclude the lowest 40% of one age group, for
example, and only 10% of another group provided the distribution varied
enough in form. The concept of the same relative amount of ability
measured in physical units, so soon as the form of distribution varies
from age to age, thus loses significance in terms of the struggle for
existence. In that struggle, a vital question is—do the individuals at
different ages have to struggle to overcome the same relative number of
opponents of better ability at their age? If they do, the individuals
might properly be regarded as in equivalent positions in the struggle
for social survival, disregarding how far the next better individual is
above them on the objective scale. This is the concept accepted by the
percentage definition of the borderline as the best available under
uncertain forms of distribution.

The recent rapid perfection of objective scales to measure educational
products, like ability in handwriting, etc., in equal units running to
an absolute zero of ability, suggests that it might be possible
ultimately to state the borderline of deficiency in terms of the same
relative objective distance between the best and zero ability at each
age on a scale of general ability. This ideal could be approached, for
example, with the Sylvester form-board test in which the units are
seconds required to complete the same task, if we could agree upon a
maximum number of seconds without success which should mean no ability,
and if this zero should remain the same at each age. It would only be
necessary to take, for example, the best position or the median or the
upper quartile at each age as the other point of reference. We could
then say that a borderline in physical units was always, for example,
.01 of the median record at each age above zero. Such a method would
provide relatively equal objective borderlines at each age and it would
afford a measure which would take into account the ability of the
individuals to be competed against instead of merely counting them as
the percentage method must. It would be better than a description in
units of the standard deviation in that its significance would be more
easily understood if the form of distribution varied with age.

To demonstrate its worth, however, this method of defining the
borderline in terms of _the same proportion of the physical difference
between zero and the median at each age_, would also have to provide a
better prediction of ultimate social failure. It would have to be shown
that individuals below the relative objective borderline at maturity
were below the same relative objective borderline during immaturity.
Moreover, it would have to be shown that this relationship was closer
than it would be with percentile records. It is a form of this relative
objective measurement which Otis advocates in his “absolute intelligence
quotient,” which he proposes as logically the best measure of ability.
It consists of the ratio of the score of the individual measured in
equal absolute units of intelligence, divided by his age (_163_).

While a relative objective borderline might under certain circumstances
afford a better criterion than the same lowest percentage of
individuals, there are two very serious practical difficulties which at
present make it impossible. In the first place, with the exception of a
few motor tests, there are no test results with children of different
ages measured in terms of equal objective units for the same task. Even
if the Binet year units are equal, as applied to the same task, there is
no accurate means of dividing the year units into smaller physical units
on the basis of scores with the tests. This makes the use of the Binet
scale impossible and we should be forced back upon such tests as the
form-board, the ergograph, etc., for which we should have to agree upon
an absolute zero of ability. Moreover, mental tests do not lend
themselves to measurement in terms merely of rapidity in doing the same
task or in terms of other equal physical units since the quality of the
work also has to be evaluated and this is usually done in units assumed
arbitrarily to measure equivalent degrees of perfection.

The second practical difficulty which at present makes a relative
objective borderline impossible is that we know nothing as to the
prediction of social failure and success from relative positions on the
objective scale used even with the few isolated tests that might be made
available. Until we have data on this question, as well as scales of
tests for native ability that are measurable to zero ability in
objective terms, the percentage method affords the only available way of
stating equivalent borderlines when the form of distribution changes.

If the age of arrest of development shifts either earlier or later with
different degrees of capacity, then there seems to be no logical escape
from a change in the form of distribution. Stern recognized this when he
concluded that idiots reach an arrest of development earlier than those
better endowed, so he stated that his quotient would not hold for them.
He said:

  “The feeble-minded child, it must be remembered, not only has a
  slower rate of development than the normal child, but also reaches a
  stage of arrest at an age when the normal child's intelligence is
  still pushing forward in its development. At this time, then, the
  cleft between the two will be markedly widened.

  “From this consideration it follows that the mental quotient can
  hold good as an index of feeble-mindedness only during that period
  when the development of the feeble-minded individual is still in
  progress. It is for this reason that there is no use in calculating
  the quotient for idiots, because, in their case the stage of
  arrested development has been entered upon long before the ages at
  which they are being subjected to examination” (_188_).

Perhaps the most interesting characteristic of the percentage method is
that it automatically adjusts itself to any form of distribution. In
case the distributions of ability turn out to be normal for each age and
the arrests of development for different degrees of ability distribute
alike, then the borderline fixed by the percentage method becomes
identical with the corresponding borderlines by the quotient, deviation,
or relative objective distance. It can be directly translated into a
quotient or a multiple of the standard deviation. This fact affords a
good check upon the empirical borderlines fixed by the percentage method
for different ages. If the distribution is normal, the lowest 1.5% and
0.5% would be identical with -2.17 S. D. and -2.575 S. D. in samples of
10,000 cases. We may check these percentage borderlines by Goddard's
results for ages 5-11 tested with the 1908 Binet scale. I have given the
standard deviation for the ages 5-11 with this data in Chap. XIII a, 2.
Applying the criterion of 2.575 S. D. to these deviations, we find that
to be in the lowest 0.5%, if the distribution were normal, would be
about a year less of deficiency than we have suggested, while Pearson's
borderline of -4 S. D. would be close to that we suggest. The empirical
data thus suggest that the assumption of a normal distribution is faulty
at the borderline or else Goddard's data is incorrect for fixing the
limits on the scales. I have already given the evidence for supposing
that the distribution is skewed during the years of growth.

When approximately random samples are not available, a multiple of the
deviation of an efficient group such as -4 S. D. at the particular age
seems to afford a practical way of discovering a tentative borderline
until a random sample can be measured. The serious theoretical
objections to such a procedure as a regular method is that the efficient
group would be selected by the subjective standard of somebody's opinion
and that the form of distribution of ability may vary from age to age.

Recalling the practical advantages of the percentage method which we
enumerated in the preceding section, we can now better understand the
value of a method that is not disturbed by the form of distribution of
mental capacity which may ultimately be found to prevail at different
ages. It is safer at present to assume that the distributions do change
enough in form at the lower end seriously to affect the borderlines of
deficiency as defined by other methods. If, however, the form of
distribution remains uniform, it would first be necessary for those
advocating the use of any of the other quantitative definitions to show
that the units of their scales are equal under some reasonable
hypothesis. A ratio or a deviation statable only in scale units which
are not demonstrably equal is a hazard, with the chances badly weighted
against its reliability. So far as both the Binet and the Point scales
are concerned we have found that the units are not equal. A quotient or
coefficient arrived at by assuming their equality is sure to mean
seriously erroneous fluctuations in the borderlines.

Referring to the percentage method, Yerkes and Wood say: “Frequency of
occurrence is unquestionably a useful datum, which should be presented,
if not instead of, then in addition to, certain other statistical
indices which possess greater scientific value” (_226_). These other
indices require both equal scale units and uniform distributions from
age to age. The ratio and deviation methods fail at present in both of
these particulars, so that it seems necessary to depend upon the
percentage definition of tested deficiency, incomplete as that may be.

This leaves us in the unfortunate situation that the borderline
positions on the scale will have to be stated separately for each age
and will have to be found empirically. Moreover, we shall need to
determine more accurately in what lowest percentage an individual must
test in order reasonably to predict that he will require social care for
the good of himself and society.

As soon as anybody can discover a means of defining the borderline,
which is equally accurate and significant, and which, in addition to
counting the proportion of better individuals to be met in the
competition of life, will also evaluate the distance they are above the
borderline, we all shall be eager to accept this better criterion of
deficiency. A form which it might take is that of relative objective
distance between zero and median ability. If measurable in equal
objective units, this would be independent of the form of distribution
and would improve the quantitative description of equivalent deficiency,
provided that it also forecasted future social failure as well as the
percentage method.

What form of stating the borderline of tested deficiency may ultimately
meet with approval, a verbal definition of feeble-mindedness will never
remain an ideal scientific statement until it finds expression in
quantitative terms.


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Footnote 34:

  Additional references on tested delinquents will be found as footnotes
  in Chapter VI.

                               APPENDIX I

                               TABLE XXI.


 No.│Sex│Age│Grade│     │Kuhlmann 1911, all│1911 │Other Kuhlmann or │ 1908
    │   │Mo.│     │     │ passed in lowest │Score│Goddard 1908 tests│Score
    │   │   │     │     │    age given     │     │      passed      │
   1│ F │  4│ 8 A │XI,  │XII 1,2,4,5. XV   │XII.4│XI 2. XIII 1      │XIII ⅔
    │   │   │     │     │  1,2,5           │     │                  │
   2│ M │  1│ 8 A │XI,  │XII 1,2,4,5       │XI.8 │None              │XII.0
   3│ M │ 10│ 8 A │XI,  │XII 1,2,3,4. XV   │XII.4│XIII 1            │XIII ⅔
    │   │   │     │     │  1,3,4           │     │                  │
   4│ M │  5│ 8 A │XI,  │XII 1,2,3,4. XV   │XII.2│None              │XII.2
    │   │   │     │     │  3,5             │     │                  │
   5│ M │  8│ 8 A │IX,  │X 2,3,4. XI       │XI.4 │IX 2,3,4,5. X     │XII.0
    │   │   │     │     │  1,2,3,4. XII    │     │  1,2,4. XI 2     │
    │   │   │     │     │  1,2,3,4. XV 4   │     │                  │
   6│ F │  0│ 8 A │XI,  │XII 1,2,4. XV 3   │XI.4 │None              │XII.2
   7│ M │  0│ 8 A │XI,  │XII 1,2,4. XV 1,3 │XII.0│XIII 1            │XIII
   8│ F │  4│ 8 A │XI,  │XII 1,2,3,4. XV   │XII.4│XIII 1            │XII.2
    │   │   │     │     │  3,4             │     │                  │
   9│ M │  9│ 7 A │XI,  │XII 1,2,3. XV 1,3 │XII.0│XI 2, XII 3. XIII │XI.6
    │   │   │     │     │                  │     │  1               │
  10│ M │ 10│ 8 A │XI,  │XII 1,2,4. XIII 1 │XI.8 │XI 2. XII 3       │XII.0
  11│ F │  0│ 5 B │IX,  │X 2,3,4. XI 2,3.  │X.8  │IX 2,3,4,5. X     │XII.0
    │   │   │     │     │  XII 1,2,4,5     │     │  1,2,4. XI 2     │
  12│ M │ 11│ 6 B │VIII,│IX 2,3,4,5. X 2,4.│IX.6 │VIII 1,5. IX      │X.0
    │   │   │     │     │  XI 3. XII 1     │     │  2,3,4,5. X 1. XI│
    │   │   │     │     │                  │     │  2               │
  13│ F │ 10│ 7 A │XI,  │XII 2,3,4. XV 2?  │XI.9 │XI 2. XV 1?       │XII.2
  14│ M │ 11│ 7 A │XI,  │XII 1,2,3,4       │XII.0│XI 2. XV 1?       │XII.0
  15│ F │  4│ 7 A │XII, │XV 2,3            │XII.6│XV 1.             │XIII.0
  16│ M │  8│ 7 A │XII, │XV 1              │XII.2│None              │XII.0
  17│ F │  8│ 8 B │X,   │XI 2,3,4. XII     │XI.4 │X 1.2,4. XI 2     │XII.0
    │   │   │     │     │  1,2,3,4         │     │                  │
  18│ M │  3│ 8 B │IX,  │X 2,3,4. XI       │XI.0 │VIII 1,5. IX      │XI.4
    │   │   │     │     │  1,2,3,4. XII    │     │  2,3,4. X 1,2,4. │
    │   │   │     │     │  1,2,5           │     │  XI 2            │
  19│ M │ 10│ 8 B │XII, │XV 1,4,5?         │XII.5│None              │XII.2
  20│ F │  3│ 8 B │XII, │XV 5              │XII.2│None              │XII.0
  21│ F │  3│ 8 B │XI,  │XII 2,3,4         │XI.6 │XI 2              │XI.4
  22│ F │ 11│ 8 B │XI,  │XII 2,4,5         │XI.6 │XI 2              │XI.4
  23│ F │  1│ 8 B │XI,  │XII 2,3,4,5. XV 3 │XII.4│X 1. XI 2         │XII.2
  24│ M │  2│ 8 A │XI,  │XII 1,2,3,4. XV 3 │XII.0│XI 2              │XII.2
  25│ F │  3│ 8 A │XI,  │XII 1,2,3,4. XV   │XII.4│XII 3             │XII.2
    │   │   │     │     │  1,3,5           │     │                  │
  26│ M │  2│ 8 A │XI,  │XII 1,2,3         │XI.6 │XI 2              │XI.4
  27│ M │ 11│ 6 A │X,   │XI 2,3,4,5. XII   │XI.4 │VIII 1,3,5. IX    │XI.4
    │   │   │     │     │  2,4,5           │     │  2,3,5. X 1,2,4. │
    │   │   │     │     │                  │     │  XI 2            │
  28│ F │  8│ 6 A │XI,  │XII 2,3,4,5       │XI.8 │XI 2              │XI.4
  29│ M │  4│ 7 B │XI,  │XII 2,3,4,5       │XI.6 │XI 2              │XII.0
  30│ F │  1│ 7 B │XI,  │XII 2,4. XV 1,3   │XI.8 │XI 2              │XI.6
  31│ M │  7│ 7 B │XI,  │XII 1,2,5. XV 3   │XI.8 │XI 2              │XI.6
  32│ F │  4│ 7 A │X,   │XI 3,4,5. XII 1,4.│XI.2 │X 1.2,4. XI 2     │XI.0
    │   │   │     │     │  XV 1            │     │                  │
  33│ F │  0│ 7 A │XI,  │XII 1,2,5. XV 1   │XI.8 │IX 2. X 1,2,4. XI │XI.4
    │   │   │     │     │                  │     │  2               │
  34│ F │  0│ 8 B │X,   │XI I,2,3,4. XII   │XI.6 │X 1,2,4. XI 2     │XII.2
    │   │   │     │     │  1,2,4. XV 3     │     │                  │
  35│ F │  9│ 8 A │X,   │XI 2?,3,4. XII    │XI.3 │X 1,2,4. XI 2     │XI.1
    │   │   │     │     │  2,3,5           │     │                  │
  36│ F │  8│ 8 A │XI,  │XII 1,2,3,4. XV   │XII.2│XI 2              │XII.2
    │   │   │     │     │  3,4             │     │                  │
  37│ M │  2│ 8 A │XII, │XVI               │XII.2│XIII 3            │XII.0
  38│ F │  6│ 8 A │XI,  │XII 2. XV 3?      │XII.2│None              │XII.0
  39│ M │  2│ 8 A │XII, │XV 3,4            │XII.4│None              │XII.2
  40│ F │  0│ 8 A │XII, │XV 1,3,5          │XII.6│XII 3. XIII 1     │XIII.0
  41│ F │  7│ 8 B │XII, │XV 2,3,5          │XII.6│None              │XIII.0
  42│ M │ 11│ 8 B │XI,  │XII 2,3,4, XV     │XII.4│XI 2              │XIII.0
    │   │   │     │     │  1,2,3,5         │     │                  │
  43│ F │  0│ 8 A │XI,  │                  │XI.0 │XI 2              │XI.0
  44│ F │  1│ 8 B │XI,  │XII 1,2,3,4       │XII.0│XI 2              │XII.2
  45│ M │  5│ 8 B │XI,  │XII 1,2,3,5       │XI.8 │XI 2              │XI.4
  46│ F │  7│ 8 B │XI,  │XII 1,2,3. XV 3   │XI.8 │XI 2              │XI.6
  47│ F │  1│ 8 B │XII, │XV 5              │XII.2│None              │XII.0
  48│ M │  7│ 8 B │XII, │XV 1,3            │XII.4│XII 3             │XIII.0
  49│ F │  8│ 7 B │VIII,│IX 2,3,4,5. X     │X.0  │VIII 1,5. IX      │IX.8
    │   │   │     │     │  2,3,4,5. XI 2,5 │     │  2,3,5. X 1      │
  50│ F │  0│ 7 A │XI,  │XII 1,2,3. XV 1   │XII.0│XIII 1            │XI.6
  51│ M │ 11│ 7 A │XI,  │XII 2,3,4. XV 2,3 │XII.0│XI 2              │XIII.0
  52│ F │ 11│ 8 A │XI,  │XII 2,5. XV 5?    │XI.5 │XI 2              │XI.2
  53│ M │  4│ 8 A │XI,  │XII 1,2,5. XV 4,5 │XII.0│XI 2              │XI.6
  54│ M │ 11│ 8 B │XII, │XV 5              │XII.2│None              │XII.0
  55│ F │  3│ 7 A │VII, │VIII 2,4,5. IX    │IX.4 │VI 2,6. VII3,7.   │X.8
    │   │   │     │     │  2,4. X 2,4,5. XI│     │  VIII1,3,5. IX2. │
    │   │   │     │     │  1,2. XII 1,2    │     │  X4, XI2         │
  56│ M │  1│ 8 A │XI   │XII 1,2. XV 2,3,5 │XII.0│XI 2              │XI.8
  57│ M │ 10│ 8 A │XII, │XV 1,2            │XII.4│XII 2             │XII.2
  58│ M │  0│ 8 A │XI,  │XII 2,3. XV 1,3   │XI.8 │XI 2. XII 3. XIII │XI.8
    │   │   │     │     │                  │     │  1               │
  59│ M │  0│ 8 A │XI,  │XII 1,2,4. XV 5   │XI.8 │XI 2              │XII.2
  60│ M │ 11│ 8 A │XI,  │XII 1,2,3,4. XV 2 │XII.0│None              │XII.2
  61│ M │  0│ 8 A │XII, │XV 1,2,3,4        │XII.8│XI 2. XIII 1      │XIII.0
  62│ M │  0│ 8 B │XI,  │XII 1,2,3,4. XV   │XII.4│XI 2              │XIII.0
    │   │   │     │     │  2,3,4           │     │                  │
  63│ F │ 10│ 7 A │XI,  │XII 1,4,5. XV 1   │XI.8 │XI 2. XIII 1      │XI.6
  64│ F │  0│ 7 A │XII, │XV 3              │XII.4│None              │XII.2
  65│ F │  9│ 8 A │XI,  │XII 1,2,3,4. XV   │XII.4│XI 2. XIII 1      │XIII.0
    │   │   │     │     │  1,2,3           │     │                  │
  66│ F │  7│ 8 A │XI,  │XII 1,2,3,5. XV   │XII.6│XI 2. XIII 1      │XIII.0
    │   │   │     │     │  1,3,4,5         │     │                  │
  67│ M │  3│ 8 B │XII, │XV 2,3,4?         │XII.5│None              │XIII.0
  68│ M │  4│ 8 A │XII, │XV 2              │XII.2│None              │XII.2
  69│ M │  2│ 8 A │XII, │XV 2,3?,4         │XII.5│None              │XII.2
  70│ M │  0│ 7 A │XII, │XV 2,4            │XII.4│None              │XII.2
  71│ F │  6│ 8 A │X,   │XI 1,2,3,4. XII   │XI.4 │XIII 1            │XI.6
    │   │   │     │     │  1,2. XV 3       │     │                  │
  72│ F │  2│ 8 A │XI,  │XII 1,2,3,4. XV   │XII.2│XI 2              │XII.2
    │   │   │     │     │  3,4             │     │                  │
  73│ F │ 10│ 8 A │XII, │XV 1,3,4,5        │XII.8│XIII 1            │XIII.0
  74│ F │  7│ 8 A │XI,  │XII 1,2,4,5       │XI.8 │XI 2              │XI.6
  75│ F │  4│ 7 B │XI,  │XII 1,2           │XI.4 │XI 2              │XI.4
  76│ F │  2│ 8 B │XI,  │XII 1,2,3         │XI.6 │X2. XI 2          │XII.0
  77│ F │ 11│ 7 B │X,   │XII 1,4,5         │XI.2 │IX 5. X 4. XI 1   │XI.4
  78│ F │  4│ 8 A │XII, │XV 2,3            │XII.4│None              │XIII.0
  79│ F │  8│ 8 A │XI,  │XII 2,4. XV 3,4   │XI.8 │None              │XI.6
  80│ F │  1│ 8 A │XI,  │XII 1,2,3,5       │XI.8 │XI 2              │XI.4
  81│ M │  9│ 8 A │XI,  │XII 1,2,3,4       │XI.8 │XI 2              │XII.0
  82│ F │  5│ 8 A │XII, │XV 3,4            │XII.4│XII 3             │XII.2
  83│ F │  5│ 8 A │XI,  │XV 3,4?           │XII.3│None              │XII.2
  84│ F │  1│ 6 A │XI,  │XII 1,2,4,5. XV 2 │XII.0│XI 2              │XII.2
  85│ M │  3│ 8 A │XV,  │                  │XV.0 │XIII 1            │XIII.0
  86│ M │  4│ 8 B │XI,  │XII 1,2,3,5. XV   │XII.2│XI 2. XII 3. XIIII│XIII.0
    │   │   │     │     │  1,2             │     │                  │
  87│ F │  4│ 8 A │XI,  │XII 1             │XI.2 │XI 2              │XI.2
  88│ F │  5│ 8 A │X,   │XI 2,3,4,5. XII   │XI.8 │VIII 1,3,5. IX    │XIII.0
    │   │   │     │     │  1,2             │     │  2,3,5. X 1,2,4. │
    │   │   │     │     │                  │     │  XI 2. XII 3     │
  89│ M │  0│ 8 B │XI,  │XII 2,5. XV 1,3,5 │XII.0│XII 3             │XI.4
  90│ F │  0│ 7 A │X,   │XI 2,3. XII       │XI.9 │IX 2,3,5. X 1,2,4.│XIII.0
    │   │   │     │     │  1,2,4,5. XV     │     │  XI 2. XII 3     │
    │   │   │     │     │  1,2,3,4?        │     │                  │
  91│ F │  6│ 7 A │VIII,│IX 2,3,4,5. X     │X.4  │VIII 1,3,5. IX    │XI.4
    │   │   │     │     │  2,4,5. XI 1,2,3.│     │  2,5. X 1,4      │
    │   │   │     │     │  XII 1,2         │     │                  │
  92│ F │ 11│ 8 A │X,   │XI 2,3,4. XII 2.  │XI.0 │X 1,2,4. XI 2     │XI.4
    │   │   │     │     │  XV 3            │     │                  │
  93│ F │  0│ 7 B │IX,  │X 2,3,4,5. XI 1,5.│X.8  │IX 2,3,4,5. X 1,2.│X.6
    │   │   │     │     │  XII 2,3,5       │     │  XI 2            │
  94│ F │  9│ 6 A │IX,  │X 2,3,4,5. XI     │XI.3 │IX 2,3,4,5. X     │XII.1
    │   │   │     │     │  1,3,4,5. XII    │     │  1,2,4. XI 2     │
    │   │   │     │     │  1,2,4. XV 3?    │     │                  │
  95│ M │  6│ 8 A │X,   │XI 1,2,4,5. XII   │XII.0│X 1,2,4 XI 2      │XIII.0
    │   │   │     │     │  1,2,3. XV 2,3,4.│     │                  │
  96│ M │ 10│ 7 A │XI,  │XII 1,2,4. XV     │XII.2│None              │XII.2
    │   │   │     │     │  1,3,5           │     │                  │
  97│ F │  6│ 7 B │X,   │XI 4,5. XII 2,5   │X.8  │IX 2,3,4,5. X 1,2.│X.6
    │   │   │     │     │                  │     │  XI 2            │
  98│ M │  1│ 7 A │XI,  │XII 1,2,4,5. XV   │XII.2│None              │XII.2
    │   │   │     │     │  3,4             │     │                  │
  99│ F │  1│ 8 A │XI,  │XII 1,2. XV 2,3   │XI.8 │None              │XIII.0
 100│ M │  0│ 8 A │XI,  │XII 2,3,4,5. XV   │XII.4│None              │XIII.0
    │   │   │     │     │  1,2,3           │     │                  │
 101│ F │  3│ 6 A │XI,  │XII 1,2,3?,4?,5.  │XII.4│None              │XI.7
    │   │   │     │     │  XV 1,3,4        │     │                  │
 102│ F │  3│ 8 A │XI,  │XII 1,2,4,5       │XI.8 │None              │XII.0
 103│ F │  0│ 8 A │XI,  │XII 1,2,5. XV 1,3 │XII.0│XIII 1            │XI.6
 104│ M │  0│ 8 B │XI,  │XII 2,3,4. XV 3   │XI.8 │None              │XII.2
 105│ F │ 10│ 8 A │XI,  │XII 1,2,3,4. XV 4 │XII.0│XII 3             │XII.0
 106│ F │  3│ 6 A │XII, │XV 1,3,4,5        │XII.8│XIII 1            │XIII.0
 107│ F │  1│ 8 A │IX,  │X 2,4,5. XI       │XI.4 │IX 1. X 1,2       │XIII.0
    │   │   │     │     │  2,3,4,5. XII    │     │                  │
    │   │   │     │     │  1,2,3. XV 2,3   │     │                  │
 108│ F │  8│ 8 A │IX,  │X 2,3,4,5. XI     │XI.2 │IX 2,3,5. X 1,2,4 │XI.2
    │   │   │     │     │  3,4,5. XII      │     │                  │
    │   │   │     │     │  1,2,5. XV 3     │     │                  │
 109│ F │  2│ 8 A │XI,  │XII 1,2,4,5. XV 1 │XII.0│None              │XII.0
 110│ F │  6│ 7 B │IX,  │X 2,3?,5. XI      │X.9  │IX 2,3,5. X 2,4.  │X.8
    │   │   │     │     │  2,3,4. XII 1,3. │     │  XII 3           │
    │   │   │     │     │  XV 1,3          │     │                  │
 111│ F │  2│ 6 A │XII, │XV 1,3,4,5        │XII.8│XII 3. XIII 1     │XIII.0
 112│ M │  1│ 5 A │IX,  │X 1,2,3,5. XI     │X.6  │IX 2,3,4?,5. X    │X.5
    │   │   │     │     │  2,3,4. XII 2    │     │  1,2,4?          │
 113│ F │  0│ 6 A │XI,  │XII 1,2,3. XV     │XII.2│XI 2              │XI.6
    │   │   │     │     │  1,3,4           │     │                  │
 114│ M │  8│ 8 A │XII, │XV 1,3,5          │XII.6│XIII 1            │XIII.0
 115│ F │  8│ 8 A │XI,  │XII 1,2,3,4. XV 3 │XII.0│XIII 1            │XII.2
 116│ M │  2│ 7 B │XI,  │XII 2,3,5         │XI.6 │XI 2. XII 3       │XI.4
 117│ F │  5│ 8 B │XI,  │XII 1,2,4,5       │XI.8 │XIII 1            │XI.6
 118│ M │  0│ 7 A │XII, │XV 1,2            │XII.2│None              │XII.2
 119│ F │  9│ 8 A │XV   │                  │XV.0 │None              │XIII.0
 120│ F │  9│ 8 B │XI,  │XII 1,2,3,4. XV 3 │XII.0│XI 2              │XII.2
 121│ M │  4│ 7 B │XII, │XV 1,5            │XII.2│XII 3             │XII.4
 122│ F │  3│ 8 A │XII, │XV 4,5            │XII.4│None              │XII.0
 123│ M │  5│ 8 B │XII, │                  │XII.0│None              │XII.0
 124│ M │  1│ 8 A │XII, │XV 3,4            │XII.0│None              │XII.0
 125│ M │  8│ 6 A │X,   │XI 1,2,3,4. XII   │XII.4│None              │XII.2
    │   │   │     │     │  2,4             │     │                  │
 126│ M │  8│ 8 A │XI,  │XII 2,4. XV 2,3,4 │XI.2 │X 1,2,4. XI 2     │XIII.0
 127│ F │  4│ 8 A │XI,  │XII 2,4. XV 3,4   │XII.0│XI 2              │XI.8
 128│ F │  9│ 8 A │X,   │XI 1,3,4,5. XII   │XI.8 │X 1,2,4. XI 2. XII│XII.2
    │   │   │     │     │  1,2,3,4. XV 3   │     │  3?              │
 129│ F │ 10│ 7 A │XI,  │XII1,2,3,5. XV 3,5│XII.2│XI 2              │XI.6
 130│ F │  4│ 7 B │XI,  │XII  1,2,3. XV 3  │XI.8 │None              │XI.6
 131│ M │  3│ 7 A │VII, │VIII 1,3,5. IX    │X.5  │VII 3,4,7. VIII   │XI.4
    │   │   │     │     │  1,2,3,4. X      │     │  1,3,5. IX       │
    │   │   │     │     │  2,3,4,5. XI     │     │  2,3,4,5. X 2,4. │
    │   │   │     │     │  1,4,5. XII      │     │  XIII 1          │
    │   │   │     │     │  1,2,3. XV 4?    │     │                  │
 132│ F │  3│ 7 B │VIII,│IX 1,2,3?,4,5. X  │XI.2 │IX 1,2. X 2,1,4.  │XII.
    │   │   │     │     │  1,3,4?,5. XI    │     │  XI 2? XII 3     │
    │   │   │     │     │  1,3,4,5. XII    │     │                  │
    │   │   │     │     │  1,2,3,4         │     │                  │
 133│ M │  7│ 7 A │XI,  │XII 1,2,3,5       │XI.8 │None              │XI.6
 134│ M │  1│ 8 B │VIII,│IX 1,2,3,4. X     │XI.6 │IX 2,3,4,5. X     │XIII.0
    │   │   │     │     │  1,2,3,4. XI     │     │  1,2,4. XI 2     │
    │   │   │     │     │  1,2,3,5. XII    │     │                  │
    │   │   │     │     │  2,3,4. XV 2,3   │     │                  │
 135│ F │  1│ 8 A │X,   │XI 2,3,4,5. XII   │XII.0│X 1,2,4. XI 2     │XII.2
    │   │   │     │     │  1,2,4. XV 3,4,5 │     │                  │
 136│ F │  5│ 8 A │XI,  │XII 1,2,3,4?. XV  │XII.5│XI 1. XII 3. XIII │XIII.0
    │   │   │     │     │  1,3,4,5         │     │  1               │
 137│ M │  6│ 8 I │XI,  │XII 2. XV 2       │XI.4 │XI 2              │XI.4
 138│ F │  4│ 8 A │XI,  │XII 1,4,5. XV     │XII.2│XI 2              │XI.6
    │   │   │     │     │  1,3,4           │     │                  │
 139│ M │  3│ 8 A │XII, │XV 1,3            │XII.4│None              │XII.2
 140│ M │  4│ 8 A │XI,  │XII 1,2,3. XV 3   │XI.8 │XI 2              │XI.6
 141│ F │  7│ 7 A │X,   │XI 2,3,4,5. XII   │XI.6 │X 4. XI 2         │XIII.0
    │   │   │     │     │  2,5. XV 2,3     │     │                  │
 142│ M │  0│ 8 A │XII, │XV 3,4,5          │XII.6│None              │XII.2
 143│ F │  2│ 5 A │X,   │XI I,2,3. XII 5   │X.8  │X 1,2,4. XI 2     │XI.0
 144│ M │  8│ 8 A │XII, │XV 2,3,5          │XII.6│None              │XIII.0
 145│ F │ 11│ 8 B │XII, │XV 3              │XII.2│None              │XII.2
 146│ M │ 10│ 8 A │XV   │                  │XV.0 │XIII 1            │XIII.0
 147│ F │  2│ 7 B │XI,  │XII 1,2,4,5. XV   │XII.2│XI 2              │XII.2
    │   │   │     │     │  3,5             │     │                  │
 148│ F │  7│ 8 A │XI,  │XII 1,2,3,5. XV   │XII.2│XI 2              │XI.6
    │   │   │     │     │  3,5             │     │                  │
 149│ M │  0│ 8 B │XII  │                  │XII.0│None              │XII.0
 150│ F │  4│ 8 A │XI,  │XII 2. XV 3,5     │XI.6 │XI 2              │XI.4
 151│ F │  7│ 8 A │XI,  │XII 1,2,3,4. XV 3 │XII.0│XI 2              │XII.2
 152│ F │  5│ 8 B │XI,  │XII 2,3,4,5. XV   │XII.2│XI 2. XIII 1      │XIII.0
    │   │   │     │     │  1,3             │     │                  │
 153│ M │  2│ 8 A │XII, │XV 2,3,4,5        │XII.8│None              │XIII.0
 154│ F │  0│ 4 B │VIII,│IX 2,3,4,5. X 1   │IX.0 │VII 3,4,7. VIII   │IX.0
    │   │   │     │     │                  │     │  1,3. IX 2,5. X 4│
 155│ M │  7│ 7 A │XI,  │XII 2,5           │XI.4 │XI 2              │XI.2
 156│ M │  6│ 8 B │XII, │XV 3              │XII.2│None              │XII.2
 157│ F │  0│ 8 A │XII, │XV 1,3            │XII.4│XII 3. XIII 1     │XIII.0
 158│ M │  2│ 8 B │XII, │XV 1,2,3,4        │XII.8│XII 3             │XIII.5
 159│ F │  1│ 7 B │X,   │XI 1,2,3,4. XII   │XI.6 │X 1,2,4. XI 2     │XII.0
    │   │   │     │     │  1,2,4           │     │                  │
 160│ F │  6│ 8 B │XII, │XV 3,5            │XII.4│None              │XII.2
 161│ M │  1│ 8 A │XII, │XV 1              │XII.2│XII 3. XIII 1     │XII.2
 162│ F │  4│ 8 A │XII  │                  │XII.4│XII 3?. XIII 1    │XII.2
 163│ F │  6│ 8 B │XI,  │XII 1,2,3,4. XV   │XII.2│None              │XII.2
    │   │   │     │     │  3,4             │     │                  │
 164│ F │ 10│ 8 A │XI,  │XII 1,2,5         │XI.6 │XI 2              │XI.4
 165│ M │  8│ 8 A │X,   │XI 1,2,3. XII     │XI.4 │VIII 1,3,5. IX    │XI.4
    │   │   │     │     │  2,3,4,5         │     │  2,3,4,5. X 1,4. │
    │   │   │     │     │                  │     │  XI 2            │
 166│ F │  1│ 7 A │X,   │XI 3,4,5. XII     │XI.8 │X 1,2,4. XI 2     │XII.2
    │   │   │     │     │  1,2,3,4. XV 1,3 │     │                  │
 167│ M │  8│ 6 B │XI,  │XII 2,3           │XI.8 │XI 2. XII 3       │XI.6
 168│ M │ 10│ 6 A │X,   │XI 1,3,4,5. XII   │XII.0│X 1,2,4. XI 2     │XI.6
    │   │   │     │     │  1,2,3,5. XV 2,5 │     │                  │
 169│ M │ 10│ 6 B │XI,  │XII 1,4?,5. XV 2? │XI.6 │XI 2              │XI.4
 170│ M │ 10│ 8 A │XI,  │XII 3,4,5. XV 5   │XI.8 │None              │XI.4
 171│ M │  1│ 8 A │XII, │XV 2,4            │XII.4│None              │XII.2
 172│ M │  3│ 8 A │X,   │XI 2,3,4. XI      │XI.4 │X 1,2,4           │XII.0
    │   │   │     │     │  1,2,3,4         │     │                  │
 173│ F │  4│ 8 A │X,   │XI 1,3,4,5. XII   │XII.2│X 1,2,4. XIII 1   │XII.2
    │   │   │     │     │  1,2,4,5. XV     │     │                  │
    │   │   │     │     │  1,4,5           │     │                  │
 174│ F │  2│ 8 A │XI,  │XII 1,2,4,5. XV   │XII.2│XII 3. XIII 1     │XIII.0
    │   │   │     │     │  1,3             │     │                  │
 175│ F │  4│ 8 A │XI,  │XII 1,2,4. XV 1   │XI.8 │XI 2              │XII.2
 176│ F │  4│ 8 A │XI,  │XII 1,2,4,5. XV   │XII.2│XI 1              │XII.0
    │   │   │     │     │  1,4             │     │                  │
 177│ M │  3│ 8 A │X,   │XI 1,2,3,4. XII   │XI.6 │X 1,2,4. XI 1     │XII.2
    │   │   │     │     │  1,2,4. XV 3     │     │                  │
 178│ M │  6│ 8 A │XII, │XV 1,3            │XII.4│XI 2. XII 3?. XIII│XIII.0
    │   │   │     │     │                  │     │  1               │
 179│ F │  2│ 8 B │XI,  │XII 1,2,3. XV 3   │XII.2│None              │XII.2
 180│ F │  2│ 8 B │XII, │XV 1,3            │XII.4│None              │XII.2
 181│ F │  2│ 8 B │XI,  │XII 1,2,4,5. XV   │XII.2│XI 2              │XII.2
    │   │   │     │     │  3,4             │     │                  │
 182│ F │  6│ 8 B │XI,  │XII 1,2,4,5. XV 3 │XII.0│XI 2              │XII.2
 183│ F │  0│ 8 B │XI,  │XII 2,3,4,5. XV   │XII.2│None              │XIII.0
    │   │   │     │     │  2,3             │     │                  │
 184│ M │  5│ 7 A │XI,  │XII 4,5           │XI.6 │XI 2              │XI.4
 185│ M │  2│ 7 A │XI,  │XII 2,3,4. XV 1   │XI.4 │XI 2              │XI.8
 186│ F │  9│ 7 B │XI,  │XII 2,3. XV       │XII.1│XI 2              │XIII.0
    │   │   │     │     │  1,2,3,4?        │     │                  │
 187│ M │  8│ 7 A │XII, │XV 3              │XII.2│XI 2              │XII.2
 188│ M │  2│ 7 B │XI,  │XII 1,2,4,5. XV   │XII.4│XI 2              │XIII.0
    │   │   │     │     │  1,2,3           │     │                  │
 189│ M │  4│ 7 B │XI,  │XII 2,3,4,5       │XI.8 │XI 2              │XI.4
 190│ M │  2│ 6 B │XI,  │XII 4,5           │XI.4 │IX 2,3,4,5. X     │XI.2
    │   │   │     │     │                  │     │  1,2,4. XI 2     │
 191│ F │  1│ 7 B │IX,  │X 1,2,3,4. XI 3,5.│X.6  │IX 2,3,5. X 1,2,4.│X.6
    │   │   │     │     │  XII 4,5         │     │  XI 2            │
 192│ F │  1│ 8 A │XI,  │XII 1,2,3,4. XV   │XII.2│XI 2              │XII.2
    │   │   │     │     │  1,3             │     │                  │
 193│ M │ 10│ 8 B │X,   │XI 1,2,5. XII     │XI.2 │IX 2,3,4,5. X     │XI.0
    │   │   │     │     │  2,4,5           │     │  1,2,4. XI 2     │
 194│ M │  8│ 8 B │XI,  │XII 1,2,3,4. XV   │XII.2│XI 2              │XII.2
    │   │   │     │     │  1,3             │     │                  │
 195│ M │  3│ 7 B │XI,  │XII 1,2,3. XV 1   │XI.8 │XI 2. XII 3       │XI.6
 196│ F │  2│ 8 B │XI,  │XII 2             │XI.2 │XI 2              │XI.2

                              APPENDIX II

                              TABLE XXII.

                             COUNTY, MINN.

        │Life-Age │        │ Basal  │ School │
        │         │        │        │ Grade  │
   No.  │Yr. │Mo. │Test-Age│Test-Age│Sept. 1 │         Offense
        │    │    │        │        │   of   │
        │    │    │        │        │Life-Age│
       1│   9│  10│VIII.8  │VIII[35]│     3 B│Truancy
   [36]2│  16│   7│XIII    │XIII    │    12 A│Grand larceny
       3│  10│   1│X.8     │IX[35]  │     3 A│Truancy
       4│  12│   4│XII     │XII     │     4 A│Truancy
       5│  14│   3│XII.2   │XII     │     7 A│Petit larceny
   [36]6│  14│   8│XIII    │XIII[35]│     9 B│Assault & battery
       7│  16│   3│XIII    │XIII    │     9 B│Check, no funds
       8│  15│   7│XIII    │XIII    │     7 A│Burglary
   [36]9│  15│   0│XI.6    │XI[35]  │     8 B│Petit larceny
  [36]10│   9│   9│IX.2    │VIII    │     2 B│Truancy
  [36]11│  14│   5│XII     │XII     │     9 B│Petit larceny
      12│  12│   2│XI.2    │XI      │     4 A│Incorrigibility
  [36]13│  16│   0│XIII    │XIII[35]│     8 A│Petit larceny
      14│  13│   8│IX.6    │VIII[35]│     4 B│Breaking & entering
  [36]15│  15│  10│X.6 plus│X       │     4 A│Incorrigibility
  [36]16│  15│   9│X.6     │IX[35]  │     5 B│Breaking & entering
  [36]17│  11│   1│XI.4    │XI[35]  │     5 B│Incorrigibility
  [36]18│  14│  10│XII.2   │XII     │     5 A│Indecent conduct
  [36]19│  15│  11│XIII    │XIII    │     8 A│Truancy
      20│  13│   2│VIII.4  │VII     │     3 B│Grand larceny
      21│  14│   1│XIII    │XIII    │     8 B│Petit larceny
  [36]22│  13│   9│XI.6    │XI[35]  │     6 B│Petit larceny
      23│  11│   0│XI.2    │XI      │     4 B│Incorrigibility
      24│  16│  11│XI.6    │XI      │     7 A│Petit larceny
      25│  12│   6│XI.2    │XI[35]  │     7 B│Truancy
  [36]26│  12│   9│XI.2    │X       │     4 B│Incorrigibility
        │Life-Age │        │ Basal  │ School │
   No.  │Yr. │Mo. │Test-Age│Test-Age│ Grade  │         Offense
  [36]27│  11│   0│X.4     │X       │     5 A│Petit larceny
  [36]28│  15│   7│XIII    │XIII    │     8 A│Truancy
      29│  14│   9│XII     │XII     │     5 A│Truancy
  [36]30│  11│  11│XII     │XII     │     6 B│Truancy
  [36]31│  11│   4│IX.8    │IX[35]  │     4 B│Truancy
  [36]32│  15│   7│XII     │XII     │     7  │Vagrancy
  [36]33│  13│   9│XI.4    │XI[35]  │     5  │Grand larceny
  [36]34│  13│   8│X.8     │X       │     5 A│Petit larceny
      35│  16│   6│XII.2   │XII     │     8 A│Burglary
  [36]36│  10│   8│IX.8    │VIII[35]│     3 B│Incorrigibility
  [36]37│  14│  10│XI.6    │XI[35]  │     7 B│Grand larceny
  [36]38│  13│   8│XIII.0  │XIII    │     8 B│Disorderly conduct
  [36]39│  14│   1│X.8     │X[35]   │     4 B│Truancy
      40│  15│   2│XI.6    │XI      │     7 B│Petit larceny
  [36]41│   9│   9│X.2     │X       │     4 B│Truancy
      42│  11│   5│XI.4    │XI      │     5 B│Incorrigibility
  [36]43│   7│   8│VII.6   │VII     │     2 B│Petit larceny
  [36]44│  13│  11│XI.6    │XI      │     8 B│Grand larceny
  [36]45│  15│   1│XI.6    │XI[35]  │     9 B│Burglary
      46│  13│  10│XII     │XII     │     5 B│Incorrigibility
  [36]47│  10│   6│IX.2    │IX[35]  │     5 B│Truancy
      48│  14│   1│X.2     │X[35]   │     6 B│Burglary
      49│  14│   3│XIII    │XIII[35]│     8 B│Burglary
      50│  14│   7│XII.2   │XII[35] │     8 B│Burglary
  [36]51│  13│   2│XII.2   │XII     │     8 B│Malicious destruction of
        │    │    │        │        │        │  property
      52│  13│   6│X.2     │X       │     7 B│Petit larceny
  [36]53│  13│   7│XI.6    │XI      │     6 A│Burglary
      54│  14│   3│XI.6    │XI[35]  │     5 A│Incorrigibility
      55│   6│   0│VII.8   │VII[35] │     1 B│Petit larceny
      56│  15│   0│XII.2   │XII     │     8 B│Incorrigibility
  [36]57│  12│   0│XI      │XI      │     6 A│Petit larceny
  [36]58│  15│   0│XI.4    │XI[35]  │     7 A│Petit larceny
      59│  15│   9│X.4     │X[35]   │     6 B│Petit larceny
      60│  15│   1│XIII    │XIII    │     7 A│Petit larceny
  [36]61│  11│   3│XI.4    │XI      │     4 A│Truancy
      62│  12│   0│XI      │X       │     3 A│Truancy
  [36]63│  15│   3│XIII    │XII I   │     8 B│Petit larceny
  [36]64│  16│   1│VIII.8  │VIII    │     5 B│Trespass
      65│  16│   4│XII     │XII     │     6 B│Incorrigibility
  [36]66│  15│   0│XI.4    │XI[35]  │     6 B│Trespass
  [36]67│  14│   5│IX.9    │IX[35]  │     3 A│Incorrigibility
      68│  16│   0│XI.4    │XI      │     9 B│Disorderly conduct
  [36]69│  16│   0│XIII    │XIII    │     8 B│Grand larceny
  [36]70│  15│   7│XI.4    │XI[35]  │     7 B│Jumping on train
      71│  15│   8│XI.6    │XI[35]  │     6 A│Disorderly conduct
      72│  16│   7│XIII    │XIII[35]│    10  │Taking auto.
  [36]73│  15│  11│XII.2   │XII     │     6 A│Truancy
  [36]74│  13│   1│X.4     │X[35]   │     3 A│Truancy
  [36]75│  14│  10│XI.6    │XI      │     5 A│Truancy
  [36]76│  11│   4│VIII.8  │VIII    │     3 A│Incorrigibility
  [36]77│  10│   3│XI      │XI      │     4 A│Petit larceny
  [36]78│  13│   4│X.8     │X[35]   │     4 A│Petit larceny
      79│  15│   5│XII     │XII     │     7 A│Indecent Conduct
  [36]80│  15│   4│XI.4    │XI[35]  │     5 A│Furnishing Liquor
  [36]81│  11│   0│XII     │XII     │     5 B│Malicious destruction of
        │    │    │        │        │        │  property
  [36]82│  12│   5│IX.8    │IX[35]  │     4 B│Petit larceny
  [36]83│  11│   7│XI.4    │XI      │     4 A│Truancy
      84│  13│   8│XI      │XI[35]  │     6 B│Incorrigibility
      85│  16│   4│XII     │XII     │    11 A│Petit larceny
      86│  11│   4│XI.4    │XI[35]  │     5 A│Malicious destruction of
        │    │    │        │        │        │  property
  [36]87│  13│   9│XI.4    │XI      │     6 B│Petit larceny
  [36]88│  14│   0│XI.2    │XI      │     8 A│Burglary
      89│  16│   5│X       │X       │     5 B│Taking auto plug
      90│  14│   9│XIII    │XIII    │     6 A│Petit larceny
      91│  13│  10│X.4     │X       │     4 B│Carrying dangerous weapons
  [36]92│  15│   4│XI.6    │XI[35]  │     6 B│Truancy
      93│  15│  11│XIII    │XIII    │     8 B│Truancy
      94│  12│  10│XII     │XII     │     4 B│Incorrigibility
  [36]95│  10│  10│IX.2    │VIII[35]│     3 A│Petit larceny
  [36]96│  12│   4│XII.2   │XII     │     7 B│Petit larceny
  [36]97│  15│   7│XIII    │XIII    │     9 A│Burglary
      98│  14│   9│XII     │XII     │     8 B│Incorrigibility
  [36]99│  11│   0│XI.2    │XI[35]  │     5 B│Incorrigibility
     100│  13│   7│X.2     │X       │     5 B│Petit larceny
     101│  10│   9│VIII    │VII     │     3 B│Breaking & entering
 [36]102│  15│   1│XIII    │XIII    │     7 A│Truancy
     103│  15│   5│XI.6    │XI[35]  │    10 B│Incorrigibility
     104│   9│   7│IX      │VIII[35]│     4 B│Incorrigibility
     105│  15│  10│XI.6    │XI      │     7 A│Receiving stolen property
     106│  15│  10│XII.2   │XII     │     5 B│Incorrigibility
     107│  12│   2│XII.2   │XII     │     7 B│Vagrancy
     108│  13│   1│X.8     │X       │     5 B│Truancy
 [36]109│  13│   9│X.6     │X[35]   │     5 B│Petit larceny
 [36]110│  15│  10│XI.4    │XI      │     6 A│Malicious destruction of
        │    │    │        │        │        │  property
 [36]111│  12│   6│XI.2    │XI      │     5 B│Petit larceny
     112│  10│   9│XII     │XII     │     4 A│Sweeping grain car
     113│  15│   2│XIII    │XIII    │     9 B│Trespass
     114│  12│  10│XII.2   │XII     │     5 B│Incorrigibility
     115│  14│   7│XI.6    │XI[35]  │     7 B│Incorrigibility
 [36]116│  15│  10│XI.4    │XI      │     7 A│Incorrigibility
 [36]117│  13│   9│XII     │XII     │     4 A│Incorrigibility
 [36]118│   9│   1│XI.2    │XI[35]  │     5 B│Incorrigibility
 [36]119│  16│  11│XI      │X[35]   │     7 B│Disorderly conduct
 [36]120│  13│   3│XII.2   │XII     │     6 B│Truancy
 [36]121│   9│   9│IX.6    │VIII[35]│     4 B│Sweeping grain car
 [36]122│  11│   9│X.8     │X       │     3 B│Sweeping grain car
 [36]123│  10│   3│X.2     │X       │     4 A│Truancy


Footnote 35:

  Passed all tests at the basal age. The others passed all but one test
  at the basal age.

Footnote 36:



 Ability of the feeble-minded, 74, 92, 197

 Arrest of development, see maturity

 Average curves, 280 ff

 Binet Scale, 7, 172
   Year units of, 260 ff

 Borderline of deficiency, 5, 13, 304 ff
   For the mature, 82-95, 240, 315
   For the immature, 104-110

 Causes of delinquency, 203 ff, 210 ff
   Method of studying, 218, 224 ff, 231 ff, 244

 City jails, 148

 Coefficient of intelligence, 305, 313

 Conative cases, 15, 18, 24-30, 34-40, 239, 248

 Convicts deficient, 142

 Correlation: of degree of deficiency with delinquency, 217
   Of deficiency and criminality, 220
   Significance of coefficients of, 219
   Of deficiency and juvenile delinquency, 220

 County institutions, 134, 148

 Crimes by the feeble-minded, 212, 214

 Criminal diathesis, 234

 Death rates, 30

 Deficiency, nature of, 21, 211 ff, 239
   See feeble, frequency, correlation, etc.

 Deficient delinquents, 158, 190, 199, 211 ff, 239, 246

 Delinquency, see frequency of, causes of, correlation, etc.

 Delinquents: first offenders, 165, 167
   Repeaters, 168

 Delinquents, tested: female, 128-141
   Male, 141-157

 Development curves, 252 ff., 279 ff

 Diagnosis, 6, 11, 14, 52, 90, 107, 172-176, 194, 197, 201, 241-244

 Distribution curves, 267-275, 317-323

 Doubtful cases, 18

 Employment of feeble-minded, 74-80

 Environment, 42, 225 ff

 Estimating deficiency by schooling, 190, 199

 Expert court advice, 243

 Family resemblance versus heredity, 231

 Feeble-minded not detected by tests, 14, 34-40

 Feeble-mindedness, 10, 17, 18, 20, 239
   See deficiency.

 Frequency of deficiency, 23, 47 ff., 80, 158 ff
   Effect of local conditions, 147, 152, 161, 163

 Frequency of delinquency among deficients, 211-218

 General ability, 34, 45, 282 ff

 Glen Lake Farm School, 122, 177

 Goddard's Scale, borderlines, 89, 106, 111, 313

 Goring's study of criminals, 218 ff., 231 ff

 Gruhle's method, 229

 Heredity, 229 ff., 236, 244

 Individual differences, 41, 280

 Inert cases, 15

 Instability, 15, 23

 Institutional care, 242, 246, 248

 Intellectual deficiency, 10, 17, 20

 Intelligence quotient, 304, 313

 Juvenile delinquency and deficiency, 220-223

 Juvenile delinquents, 162

 Kuhlmann's Scale, borderlines, 87-90, 111, 118

 Legal responsibility, 244

 Maturity of mind, 83, 282, 290
   Later for deficients, 294 ff., 230

 Measurement units, 254 ff., 275 ff., 317

 Mental deficiency, 11, 20
   See feeble.

 Mental development, 279 ff

 Minneapolis: delinquents tested, 125
   School retardation, 177-185, 199
   Juvenile deficient delinquents, 220-223

 Minneapolis, school group tested, 85-91

 Morons: chances of delinquency, 217
   Danger to society, 237, 246

 Normal distribution, 256, 267

 Observation home, 242

 Offenses, 168

 Percentage definition of deficiency, 5, 13, 20, 65, 75, 80, 240, 304
    ff., 307
   Advantages, 311 ff.

 Percentage feeble-minded, 47 ff.

 Percentiles as units, 276

 Point Scale, borderlines, 114, 313

 Prostitutes, 78, 129, 140, 158
   Schooling, 186

 Quantitative definitions, 21, 304 ff.
   Effect of uncertain forms of distribution, 317 ff.

 Ranks as units, 276

 Rates of development, 290 ff.

 Recidivism, 168, 235

 Reformatories, 128, 143

 Responsibility of deficients, 244

 School test of deficiency, 177, 189 ff.

 School maladjustment, 203-209, 247

 School retardation of delinquents, 177-188, 190-194, 199

 Skewed distributions, 267, 300

 Social care, 47-52, 80, 158 ff., 212-214, 216, 237, 242-251

 Social deficiency, 10, 15, 74, 239

 Special ability, 34, 45

 Special classes, 62 ff., 74-80

 Standard deviation, 256, 306, 314

 Stanford Scale, borderlines, 101, 112, 313

 State prisons, 128, 141

 State Training Schools, 131, 145

 Sterilization, 245

 Test by school retardation, 177, 189

 Tested deficiency, 13

 Tests, mental, 170 ff.
   See also Binet, Goddard, Kuhlmann, Point, and Stanford Scales.

 Thorn Hill Detention Home, 151

 Training for deficients, 205

 Units of measurement, 254, 275, 317

 Vagrancy, 158

 Variability, 41-46, 280 ff.

 Year units, 260-266

      *      *      *      *      *      *

Transcriber's note:

 1. Changed the total column in Table X on p. 151 for the life-age 8 row
    to 1 and the Totals row to 124.

 2. In TABLE XIII. on p. 179 the GIRLS Percentages columns on the
    Ordinary Pupils row only adds up to 99%.

 3. Silently corrected typographical errors.

 4. Retained anachronistic and non-standard spellings as printed.

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