Animal intelligence: Experimental studies

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Title: Animal intelligence: Experimental studies
Author: Thorndike, Edward L. (Edward Lee)
Language: English
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ANIMAL INTELLIGENCE

[Illustration]

THE MACMILLAN COMPANY
NEW YORK · BOSTON · CHICAGO
SAN FRANCISCO

MACMILLAN & CO., LIMITED
LONDON · BOMBAY · CALCUTTA
MELBOURNE

THE MACMILLAN CO. OF CANADA, LTD.
TORONTO

ANIMAL INTELLIGENCE

EXPERIMENTAL STUDIES

BY
EDWARD L. THORNDIKE
TEACHERS COLLEGE, COLUMBIA UNIVERSITY

New York
THE MACMILLAN COMPANY
1911

_All rights reserved_

Set up and electrotyped. Published June, 1911.

Norwood Press
J. S. Cushing Co.—Berwick & Smith Co.
Norwood, Mass., U.S.A.

PREFACE

The main purpose of this volume is to make accessible to students of
psychology and biology the author’s experimental studies of animal
intellect and behavior.[1] These studies have, I am informed by teachers
of comparative psychology, a twofold interest. Since they represent the
first deliberate and extended application of the experimental method in
animal psychology, they are a useful introduction to the later literature
of that subject. They mark the change from books of general argumentation
on the basis of common experience interpreted in terms of the faculty
psychology, to monographs reporting detailed and often highly technical
experiments interpreted in terms of original and acquired connections
between situation and response. Since they represent the point of view
and the method of present animal psychology, but in the case of very
general and simple problems, they are useful also as readings for
students who need a general acquaintance with some sample of experimental
work in this field.

It has seemed best to leave the texts unaltered except for the correction
of typographical errors, renumbering of tables and figures, and redrawing
the latter. In a few places, where the original text has been found
likely to be misunderstood, brief notes have been added. It is hard
to resist the impulse to temper the style, especially of the ‘Animal
Intelligence,’ with a certain sobriety and restraint. What one writes
at the age of twenty-three is likely to irritate oneself a dozen years
later, as it doubtless irritated others at the time. The charitable
reader may allay his irritation by the thought that a degree of
exuberance, even of arrogance, is proper to youth.

To the reports of experimental studies are added two new essays dealing
with the general laws of human and animal learning.

JANUARY, 1911.

CONTENTS

PAGE

THE STUDY OF CONSCIOUSNESS AND THE STUDY OF BEHAVIOR 1

ANIMAL INTELLIGENCE 20

Introduction 20

Description of Apparatus 29

Experiments with Cats 35

Experiments with Dogs 56

Experiments with Chicks 61

Reasoning or Inference 67

Imitation 76

In Chicks 81

In Cats 85

In Dogs 92

The Mental Fact in Association 98

Association by Similarity and the Formation of Concepts 116

Criticism of Previous Theories 125

Delicacy of Association 128

Complexity of Associations 132

Number of Associations 135

Permanence of Associations 138

Inhibition of Instincts by Habit 142

Attention 144

The Social Consciousness of Animals 146

Interaction 147

Applications to Pedagogy, Anthropology, etc. 149

Conclusion 153

THE INSTINCTIVE REACTIONS OF YOUNG CHICKS 156

A NOTE ON THE PSYCHOLOGY OF FISHES 169

THE MENTAL LIFE OF THE MONKEYS 172

Introduction 173

Apparatus 177

Learning without Tuition 182

Tests with Mechanisms 184

Tests with Signals 195

Experiments on the Influence of Tuition 209

Introduction 209

Imitation of Human Beings 211

Imitation of Other Monkeys 219

Learning apart from Motor Impulses 222

General Mental Development of the Monkeys 236

LAWS AND HYPOTHESES OF BEHAVIOR 241

THE EVOLUTION OF THE HUMAN INTELLECT 282

ANIMAL INTELLIGENCE

CHAPTER I

THE STUDY OF CONSCIOUSNESS AND THE STUDY OF BEHAVIOR

The statements about human nature made by psychologists are of two
sorts,—statements about _consciousness_, about the inner life of
thought and feeling, the ‘self as conscious,’ the ‘stream of thought’;
and statements about _behavior_, about the life of man that is left
unexplained by physics, chemistry, anatomy and physiology, and is roughly
compassed for common sense by the terms ‘intellect’ and ‘character.’

Animal psychology shows the same double content. Some statements concern
the conscious states of the animal, what he is to himself as an inner
life; others concern his original and acquired ways of response, his
behavior, what he is to an outside observer.

Of the psychological terms in common use, some refer only to conscious
states, and some refer to behavior regardless of the consciousness
accompanying it; but the majority are ambiguous, referring to the man or
animal in question, at times in his aspect of inner life, at times in his
aspect of reacting organism, and at times as an undefined total nature.
Thus ‘intensity,’ ‘duration’ and ‘quality’ of sensations, ‘transitive’
and ‘substantive’ states and ‘imagery’ almost inevitably refer to states
of consciousness. ‘Imitation,’ ‘invention’ and ‘practice’ almost
inevitably refer to behavior observed from the outside. ‘Perception,’
‘attention,’ ‘memory,’ ‘abstraction,’ ‘reasoning’ and ‘will’ are samples
of the many terms which illustrate both ways of studying human and animal
minds. That an animal perceives an object, say, the sun, may mean either
that his mental stream includes an awareness of that object distinguished
from the rest of the visual field; or that he reacts to that object as a
unit. ‘Attention’ may mean a clearness, focalness, of the mental state;
or an exclusiveness and devotion of the total behavior. It may, that
is, be illustrated by the sharpness of objects illumined by a shaft of
light, or by the behavior of a cat toward the bird it stalks. ‘Memory’
may be consciousness of certain objects, events or facts; or may be
the permanence of certain tendencies in either thought or action. ‘To
recognize’ may be to feel a certain familiarity and surety of being able
to progress to certain judgments about the thing recognized; or may be to
respond to it in certain accustomed and appropriate ways. ‘Abstraction’
may refer to ideas of qualities apart from any consciousness of their
concrete accompaniments, and to the power of having such ideas; or to
responses to qualities irrespective of their concrete accompaniments,
and to the power of making such responses. ‘Reasoning’ may be said
to be present when certain sorts of consciousness, or when certain
sorts of behavior, are present. An account of ‘the will’ is an account
of consciousness as related to action or an account of the actions
themselves.

Not only in psychological judgments and psychological terms, but also
in the work of individual psychologists, this twofold content is seen.
Amongst writers in this country, for example, Titchener has busied
himself almost exclusively with consciousness ‘as such’; Stanley Hall,
with behavior; and James, with both. In England Stout, Galton and Lloyd
Morgan have represented the same division and union of interests.

On the whole, the psychological work of the last quarter of the
nineteenth century emphasized the study of consciousness to the
neglect of the total life of intellect and character. There was a
tendency to an unwise, if not bigoted, attempt to make the science
of human nature synonymous with the science of facts revealed by
introspection. It was, for example, pretended that the only value of all
the measurements of reaction-times was as a means to insight into the
reaction-consciousness,—that the measurements of the amount of objective
difference in the length, brightness or weight of two objects that men
could judge with an assigned degree of correctness were of value only so
far as they allowed one to infer something about the difference between
two corresponding consciousnesses. It was affirmed that experimental
methods were not to aid the experimenter to know what the subject did,
but to aid the subject to know what he experienced.

The restriction of studies of human intellect and character to studies
of conscious states was not without influence on scientific studies
of animal psychology. For one thing, it probably delayed them. So
long as introspection was lauded as the chief method of psychology, a
psychologist would tend to expect too little from mere studies, from the
outside, of creatures who could not report their inner experiences to
him in the manner to which he was accustomed. In the literature of the
time will be found many comments on the extreme difficulty of studying
the psychology of animals and children. But difficulty exists only in the
case of their _consciousness_. Their _behavior_, by its simpler nature
and causation, is often far easier to study than that of adults. Again,
much time was spent in argumentation about the criteria of consciousness,
that is, about what certain common facts of behavior meant in reference
to inner experience. The problems of inference about consciousness
from behavior distracted attention from the problems of learning more
about behavior itself. Finally, when psychologists began to observe
and experiment upon animal behavior, they tended to overestimate the
resulting insight into the stream of the animal’s thought and to neglect
the direct facts about what he did and how he did it.

Such observations and experiments are, however, themselves a means of
restoring a proper division of attention between consciousness and
behavior. A psychologist may think of himself as chiefly a stream of
consciousness. He may even think of other men as chiefly conscious
selves whose histories they report by word and deed. But it is only by
an extreme bigotry that he can think of a dog or cat as chiefly a stream
or chain or series of consciousness or consciousnesses. One of the lower
animals is so obviously a bundle of original and acquired connections
between situation and response that the student is led to attend to the
whole series,—situation, response and connection or bond,—rather than
to just the conscious state that may or may not be one of the features
of the bond. It is so useful, in understanding the animal, to see what
it does in different circumstances and what helps and what hinders its
learning, that one is led to an intrinsic interest in varieties of
behavior as well as in the kinds of consciousness of which they give
evidence.

What each open-minded student of animal psychology at first hand comes
thus to feel vaguely, I propose in this essay to try to make definite
and clear. The studies reprinted in this volume produced in their
author an increased respect for psychology as the science of behavior, a
willingness to make psychology continuous with physiology, and a surety
that to study consciousness for the sake of inferring what a man can or
will do, is as proper as to study behavior for the sake of inferring what
conscious states he can or will have. This essay will attempt to defend
these positions and to show further that psychology may be, at least in
part, as independent of introspection as physics is.

A psychologist who wishes to broaden the content of the science to
include all that biology includes under the term ‘behavior,’ or all that
common sense means by the words ‘intellect’ and ‘character,’ has to meet
certain objections. The first is the indefiniteness of this content.

The indefiniteness is a fact, but is not in itself objectionable. It is
true that by an animal’s behavior one means the facts about the animal
that are left over after geometry, physics, chemistry, anatomy and
physiology have taken their toll, and that are not already well looked
after by sociology, economics, history, esthetics and other sciences
dealing with certain complex and specialized facts of behavior. It is
true that the boundaries of psychology, from physiology on the one hand,
and from sociology, economics and the like on the other, become dubious
and changeable. But this is in general a sign of a healthy condition
in a science. The pretense that there is an impassable cleft between
physiology and psychology should arouse suspicion that one or the other
science is studying words rather than realities.

The same holds against the objection that, if psychology is the science
of behavior, it will be swallowed up by biology. When a body of facts
treated subjectively, vaguely and without quantitative precision by one
science or group of scientists comes to be treated more objectively,
definitely and exactly by another, it is of course a gain, a symptom
of the general advance of science. That geology may become a part of
physics, or physiology a part of chemistry, is testimony to the advance
of geology and physiology. Light is no less worthy of study by being
found to be explainable by laws discovered in the study of electricity.
Meteorology had to reach a relatively high development to provoke the wit
to say that “All the science in meteorology is physics, the rest is wind.”

These objections to be significant should frankly assert that between
physical facts and mental facts, between bodies and minds, between any
and all of the animal’s movements and its states of consciousness,
there is an impassable gap, a real discontinuity, found nowhere else in
science; and that by making psychology responsible for territory on both
sides of the gap, one makes psychology include two totally disparate
groups of facts, things and thoughts, requiring totally different methods
of study. This is, of course, the traditional view of the scope of
psychology, reiterated in the introductions to the standard books and
often accepted in theory as axiomatic.

It has, however, already been noted that in practice psychologists do
study facts in disregard of this supposed gap, that the same term refers
to facts belonging some on one side of it and some on the other, and
that, in animal psychology, it seems very unprofitable to try to keep
on one side or the other. Moreover, the practice to which the study of
animal and child psychology leads is, if I understand their writings,
justified as a matter of theory by Dewey and Santayana. If then, as a
matter of scientific fact, human and animal behavior, with or without
consciousness, seems a suitable subject for a scientific student, we may
study it without a too uneasy sense of philosophic heresy and guilt.

The writer must confess not only to the absence of any special reverence
for the supposed axiom, but also to the presence of a conviction that it
is false, the truth being that whatever feature of any animal, say John
Smith, of _Homo sapiens_, is studied—its length, its color of hair, its
body temperature, its toothache, its anxiety, or its thinking of 9 ×
7—the attitude and methods of the student may properly be substantially
the same.

Of the six facts in the illustration just given, the last three would by
the traditional view be all much alike for study, and all much unlike any
of the first three. The same kind of science, physical science, would be
potent for the first three and impotent for the last three (save to give
facts about certain physical facts which ‘paralleled’ them). Conversely
one kind of science, psychology, would by the traditional view deal with
the last three, but have nothing to say about the first three.

But is there in actual fact any such radical dichotomy of these six facts
as objects of science? Take any task of science with respect to them, for
example, identification. A score of scientific men, including John Smith
himself, are asked to identify John’s stature at a given moment. Each
observes it carefully, getting, let us say, as measures: 72.10 inches,
72.11, 72.05, 72.08, 72.09, 72.11, etc.

In the case of color of hair each observes as before, the reports being
brown, light brown, brown, light brown, between light brown and brown,
and so forth.

In the case of body temperature, again, each observes as before, there
being the same variability in the reports; but John _may also observe
in a second way_, not by observing a thermometer with eyes, but by
observing the temperature of his body through other sense-organs so
situated that they lead to knowledge of only his own body’s temperature.
It is important to note that for efficient knowledge of his own
body-temperature, John does not use the sense approach peculiar to him,
but that available for all observers. He identifies and measures his
‘feverishness’ by studying himself as he would study any other animal, by
thermometer and eye.

In the case of the toothache the students proceed as before, except
that they use John’s gestures, facial expression, cries and verbal
reports, as well as his mere bodily structure and condition. They not
only observe the cavities in his teeth, the signs of ulcer and the like,
but they also ask him, tapping a tooth, “Does it hurt?” “How long has
it hurt?” “Does it hurt very much?” and the like. John, if their equal
in knowledge of dentistry, would use the same methods, testing himself,
asking himself questions and using the replies made by himself to himself
in inner speech. But, as with temperature, he would get data, for his
identification of the toothache, from a source unavailable for the
others, the sense-organs in his teeth.

It is worth while to consider how they and he would proceed to an exact
identification or measure of the intensity of his toothache such as was
made of his stature or body-temperature. First, they would need a scale
of toothaches of varying intensities. Next, they would need means of
comparing the intensity of his toothache with those of this scale to see
which it was most like. Given this scale and means of comparison, they
would turn John’s attention from the original toothache to one of given
intensity, and compare the two, both by his facial expression, gestures
and the like, and by the verbal reports made. John would do likewise,
reporting to himself instead of to them. The similarity of the procedure
to that in studying a so-called physical fact is still clearer if we
suppose a primitive condition of the scales of length and temperature.
Suppose for example that for the length of a man we had only ‘short’ or
‘tall as a deer,’ ‘medium’ or ‘tall as a moose,’ and ‘tall’ or ‘tall
as a horse’; and for the intensity of the toothache of a man ‘little’
or ‘intense as a pin-prick,’ ‘medium’ or ‘intense as a knife-cut,’
and ‘great’ or ‘intense as a spear-thrust.’ Then obviously the only
difference between the identification of the length of a man’s body and
the identification of the intensity of his toothache would be that the
latter was made by all on the basis of behavior as well as anatomy, and
made by the individual having it on the basis of data from an additional
sense-organ.

In actual present practice, if observers were asked to identify the
intensity of John’s toothache on a scale running from zero intensity
up, the variability of the reports would be very great in comparison
with those of stature or body-temperature. Supposing the most intense
toothache to be called _K_, we might well have reports of from say .300
_K_ to .450 _K_, some observers identifying the fact with a condition
one and a half times as intense as that chosen by others. But such a
variability might also occur in primitive men’s judgments of length or
temperature.

It is important to note that the accuracy of John’s own identification
of it depends in any case on his knowledge of the scale and his power of
comparing his toothache therewith. Well-trained outside observers might
identify the intensity of John’s toothache more accurately than he could.

In the case of John’s anxiety, the most striking fact is the low degree
of accuracy in identification. The quality of the anxiety and its
intensity would both be so crudely measured by present means that even if
the observers were from the score of most competent psychologists, their
reports would probably be not much better than, say, the descriptions
now found in masterpieces of fiction and drama. Science could not
tell at all closely how much John’s anxiety at this particular time
resembled either his anxiety on some other occasion or anything else.
This inferiority is due in part to the fact that the manifestations
of anxiety in behavior, including verbal reports, are so complicated
by facts other than the anxiety itself, by, for example, the animal’s
health, temperament, concomitant ideas and emotions, knowledge of
language, clearness in expression and the like. It is due in part to
the very low status of our classification of kinds of anxieties and
of our units and scales for measuring the amount of each kind. Hence
the variation amongst observers would be even greater than in the case
of the toothache, and the confidence of all in their judgments would
be less, and far, far less than their confidence in their judgment of
John’s stature. The best possible present knowledge of John’s anxiety,
though scientific in comparison with ordinary opinion about it, would
seem grossly unscientific in comparison with knowledge of his stature or
weight. Knowledge of the anxiety would improve with better knowledge of
its manifestations, including verbal reports by John, and with better
means of classification and measurement.

John’s knowledge of his own anxiety would be in part the same as that of
the other observers. He too would judge his condition by its external
manifestations, would name its sort and rate its amount on the basis of
his own behavior, as he saw his own face, heard his own groans, and read
the notes he wrote describing his condition. But he would also, as with
the toothache, have data from internal sense-organs and perhaps from
centrally initiated neural actions. In so far as he could report these
data to himself for use in scientific thought more efficiently than he
could report them to the other observers, he would have, as with the
toothache, an advantage comparable to the advantage of a criminologist
who happened also to be or to have been a thief, or of a literary critic
who happened to have written what he judged. It is important to note that
only in so far as he who has ‘immediate experience’ of or participates
in or is ‘directly conscious’ of the anxiety, reports it to himself as
thinker or scientific student, in common with the other nineteen, that
this advantage accrues. To really _be_ or _have_ the anxiety is not to
correctly _know_ it. An insane man must become sane in order to know
his insane condition. Bigotry, stupidity and false reasoning can be
understood only by one who never was them or has ceased to be them.

In our last illustration, John’s thinking of ‘9 × 7 equals 63,’ the
effect on John’s behavior may be so complicated by other conditions
in John, and is so subject to the particular conditions which we name
John’s ‘will,’ that the observers would often be at loss except for
John’s verbal report. Not that the observer is restricted to that. If
John does the example 217 × 69 in the usual way, it is a very safe
inference that he thought 9 × 7 equals 63, regardless of the absence of a
verbal report from him. But often there is little else to go by. To John
himself, on the contrary, it is easier to be sure that he is thinking
of 9 × 7 equals 63, than that he has a particular sort and strength of
toothache. Consequently if we suppose John to be thinking of that fact
while under observation, and the twenty observers to be required to
identify the fact he is thinking of, it is sure that there might be an
enormous variability in their guesses as to what the fact was and that
his testimony might be worth far more than that of all the other nineteen
without his testimony. His observation is influenced by the action of
the neurones in his central nervous system as theirs is not, and, in the
case of the thought ‘9 × 7 equals 63,’ the action of these neurones is of
special importance.

Our examination of the way science treats these six facts shows no
impassable cleft between knowledge of a man’s body and knowledge of his
mind. Scientific statements about the toothache, anxiety and numerical
judgment are in general more variable than statements about length,
hair-color and body-temperature, but there is here no difference save of
degree. Some physical facts, such as hair-color, eye-color or health,
are, in fact, judged more variably than some mental facts, such as rate
of adding, accuracy of perception of a certain sort and the like. So
far as the lack of agreement amongst impartial observers goes, there is
continuity from the identification of a length to that of an ideal.

Scientific judgments about the facts of John’s mind also depend, in
general, more upon his verbal reports than do judgments about his body.
But here also the difference is only of degree. The physician studying
wounds, ulcers, tumors, infections and other facts of a man’s body
may depend more upon his verbal reports than does the moralist who is
studying the man’s character. Verbal reports too are themselves a gradual
and continuous extension of coarser forms of behavior. They signify
consciousness no more truly than do signs, gestures, facial expression
and the general bodily motions of pursuit, retreat, avoidance or seizure.

Nor is it true that physical facts are known to many observers and mental
facts to but one, who _is_ or _has_ or _directly experiences_ them. If it
were true, sociology, economics, history, anthropology and the like would
either be physical sciences or represent no knowledge at all. The kind of
knowledge of which these sciences and the common judgments of our fellow
men are made up is knowledge possessed by many observers in common, the
individual of whom the facts is known, knowing the fact in part in just
the same way that the others know it.

The real difference between a man’s scientific judgments about himself
and the judgment of others about him is that he has _added sources of
knowledge_. Much of what goes on in him influences him in ways other
than those in which it influences other men. But this difference is not
coterminous with that between judgments about his ‘mind’ and about his
‘body.’ As was pointed out in the case of body-temperature, a man knows
certain facts about his own body in such additional ways.

Furthermore, there is no more truth in the statement that a man’s
pain or anxiety or opinions are matters of direct consciousness, pure
experience, than in the statement that his length, weight and temperature
are, or that the sun, moon and stars are. If by the pain we must mean
the pain as felt by some one, then by the sun we can mean only the sun
as seen by some one. Pain and sun are equally subjects for a science of
‘consciousness as such.’ But if by the sun is meant the sun of common
sense, physics and astronomy, the sun as known by any one, then by the
pain we can mean the pain of medicine, economics and sociology, the pain
as known by any one, and by the sufferer long after he _was_ or _had_ it.

All facts emerge from the matrix of pure experience; but they become
facts for science only after they have emerged therefrom. A man’s anxiety
may be the anxiety as directly felt by the man, or as thought of by him,
or as thought of by the general consensus of scientific observers. But
so also may be his body-temperature or weight or the composition of the
blood in his veins. There can be no valid reason other than a pragmatic
one for studying a man’s anxiety solely as _felt_ by him while studying
his body-temperature as _thought of_ by him and others. And the practical
reasons are all in favor of studying all facts as they exist for any
impartial observer. A man’s mind as it is to thinking men is all that
thinking men can deal with and all that they have any interest in dealing
with.

Finally, the subject-matter of psychology is not sharply marked off from
the subject-matter of physiology by being absolutely non-spatial. On the
contrary, the toothache, anxiety and judgment are referred unequivocally,
by every sane man who thinks of them, to the space occupied by the body
of the individual in question. That is the surest fact about them.
It is true that we do not measure the length, height, thickness and
weight of an animal’s pain or anxiety, but neither do we those of his
pulse, temperature, health, digestion, metabolism, patellar reflex or
heliotropism.

Two noteworthy advantages are secured by the study of behavior. First,
the evidence about intellect and character offered by action and the
influence of intellect and character upon action are given due attention.
Second, the connections of conscious states are studied as well as their
composition.

The mind or soul of the older psychology was the cause not only of
consciousness, but also of modifiability in thought and action. It was
the substance or force in man whereby he was sensitive to certain
events, was able to make certain movements, and not only had ideas but
connected them one with another and with various impressions and acts.
It was supposed to account for actual bodily action as well as for the
action-consciousness. It explained the connections between ideas as well
as their internal composition. If a modern psychologist defines mind
as the sum total of consciousness, and lives up to that definition, he
omits the larger portion of the task of his predecessors. To define our
subject-matter as the nature and behavior of men, beginning where anatomy
and physiology leave off, is, on the contrary, to deliberately assume
responsibility for the entire heritage. Behavior includes consciousness
_and_ action, states of mind _and_ their connections.

Even students devoted to ‘consciousness as such’ must admit that the
movements of an animal and their connections with other features of
his life deserve study, by even their kind of psychologist. For the
fundamental means of knowing that an animal has a certain conscious
state are knowledge that it makes certain movements and knowledge of
what conscious states are connected with those movements. Knowledge of
the action-system of an animal and its connections is a prerequisite to
knowledge of its stream of consciousness.

There are better reasons for including the action-system of an animal in
the psychologist’s subject-matter. An animal’s conscious stream is of
no account to the rest of the world except in so far as it prophesies
or modifies his action.[2] There can be no moral warrant for studying
man’s nature unless the study will enable us to control his acts. If
a psychologist is to study man’s consciousness without relation to
movement, he might as well fabricate imaginary consciousnesses to
describe and analyze. The lovers of consciousness for its own sake often
do this unwittingly, but would scarcely take pride therein!

The truth of the matter is, of course, that an animal’s mind is, by any
definition, something intimately associated with his connection-system
or means of binding various physical activities to various physical
impressions. The whole series—external situations and motor responses as
well as their bonds—must be studied to some extent in order to understand
whatever we define as mind. The student of behavior, by frankly accepting
the task of supplying any needed information not furnished by physiology,
and of studying the animal in action as well as in thought, is surer of
getting an adequate knowledge of whatever features of an animal’s life
may be finally awarded the title of mind.

The second advantage in studying total behavior rather than consciousness
as such is that thereby the connections of mental facts one with another
and with non-mental facts receive due attention.

The original tendencies to connect certain thoughts, feelings and acts
with certain situations—tendencies which we call reflexes, instincts
and capacities—are not themselves states of consciousness; nor are
the acquired connections which we call habits, associations of ideas,
tendencies to attend, select and the like. No state of consciousness
bears within itself an account of when and how it will appear, or of
what bodily act will be its sequel. What any given person will think in
any given situation is unpredictable by mere descriptions and analyses
of his previous thoughts each by itself. To understand the _when_, _how_
and _why_ of states of consciousness one must study other facts than
states of consciousness. These non-conscious relations or connections,
knowledge of which informs us of the result to come from the action of a
given situation on a given animal, may be expected to be fully half of
the subject-matter of mental science.

As was noted in the early pages of this chapter, the psychologist
commonly does adopt the attitude of treating mind as a system of
connections long enough to give some account of the facts of instinct,
habit, memory, and the like. But the dogma that psychology deals
exclusively with the inner stream of mind-stuff has made these accounts
needlessly scanty and vague.

One may appreciate fully the importance of finding out whether the
attention-consciousness is clearness or is something else, and whether
it exists in two or three discrete degrees or in a continuous series of
gradations, and still insist upon the equal importance of finding out
to what facts and for what reasons human beings do attend. There would
appear, for example, to be an unfortunate limitation to the study of
human nature by the examination of its consciousnesses, when two eminent
psychologists, writing elaborate accounts of attention from that point of
view, tell us almost nothing whereby we can predict what any given animal
will attend to in any given situation, or can cause in any given animal a
state of attention to any given fact.

One may enjoy the effort to define the kind of mind-stuff in which one
thinks of classes of facts, relations between facts and judgments about
facts, and still protest that a proper balance in the study of intellect
demands equal or greater attention to the problems of why any given
animal thinks of any given fact, class or relation in any given situation
and why he makes this or that judgment about it.

In the case of the so-called action-consciousness the neglect of
the connections becomes preposterous. The adventitious scraps of
consciousness called ‘willing’ which may intervene between a situation
productive of a given act and the act itself are hopelessly uninstructive
in comparison with the bonds of instinct and habit which cause the
situation to produce the act. In conduct, at least, that kind of
psychology which Santayana calls ‘the perception of character’ seems an
inevitable part of a well-balanced science of human nature. I quote from
his fine description of the contrast between the external observation
of a mind’s connections and the introspective recapitulation of its
conscious content, though it is perhaps too pronounced and too severe.

“_Perception of Character._—There is, however, a wholly different and
far more positive method of reading the mind, or what in a metaphorical
sense is called by that name. This method is to read character. Any
object with which we are familiar teaches us to divine its habits; slight
indications, which we should be at a loss to enumerate separately,
betray what changes are going on and what promptings are simmering in
the organism.... The gift of reading character ... is directed not upon
consciousness but upon past or eventual action. Habits and passions,
however, have metaphorical psychic names, names indicating dispositions
rather than particular acts (a disposition being mythically represented
as a sort of wakeful and haunting genius waiting to whisper suggestions
in a man’s ear). We may accordingly delude ourselves into imagining that
a pose or a manner which really indicates habit indicates feeling instead.

“_Conduct Divined, Consciousness Ignored._... As the weather prophet
reads the heavens, so the man of experience reads other men. Nothing
concerns him less than their consciousness; he can allow that to run
itself off when he is sure of their temper and habits. A great master of
affairs is usually unsympathetic. His observation is not in the least
dramatic or dreamful, he does not yield himself to animal contagion
or reënact other people’s inward experience. He is too busy for that,
and too intent on his own purposes. His observation, on the contrary,
is straight calculation and inference, and it sometimes reaches truths
about people’s character and destiny which they themselves are very far
from divining. Such apprehension is masterful and odious to weaklings,
who think they know themselves because they indulge in copious soliloquy
(which is the discourse of brutes and madmen), but who really know
nothing of their own capacity, situation, or fate.”[3]

Mr. Santayana elsewhere hints that both psychology and history will
become studies of human behavior considered from without,—a part, that
is, of what he calls physics,—if they are to amount to much.

Such a prediction may come true. But for the present there is no need
to decide which is better—to study an animal’s self as conscious, its
stream of direct experience, or to study the intellectual and moral
nature that causes its behavior in thought and action and is known to
many observers. Since worthy men have studied both, both are probably
worthy of study. All that I wish to claim is the right of a man of
science to study an animal’s intellectual and moral behavior, following
wherever the facts lead—to “the sum total of human experience considered
as dependent upon the experiencing person,” to the self as conscious, or
to a connection-system known to many observers and born and bred in the
animal’s body.

CHAPTER II

ANIMAL INTELLIGENCE; AN EXPERIMENTAL STUDY OF THE ASSOCIATIVE PROCESSES
IN ANIMALS[4]

This monograph is an attempt at an explanation of the nature of the
process of association in the animal mind. Inasmuch as there have been no
extended researches of a character similar to the present one either in
subject-matter or experimental method, it is necessary to explain briefly
its standpoint.

Our knowledge of the mental life of animals equals in the main our
knowledge of their sense-powers, of their instincts or reactions
performed without experience, and of their reactions which are built up
by experience. Confining our attention to the latter, we find it the
opinion of the better observers and analysts that these reactions can
all be explained by the ordinary associative processes without aid from
abstract, conceptual, inferential thinking. These associative processes
then, as present in animals’ minds and as displayed in their acts, are
my subject-matter. Any one familiar in even a general way with the
literature of comparative psychology will recall that this part of the
field has received faulty and unsuccessful treatment. The careful, minute
and solid knowledge of the sense-organs of animals finds no counterpart
in the realm of associations and habits. We do not know how delicate
or how complex or how permanent are the possible associations of any
given group of animals. And although one would be rash who said that our
present equipment of facts about instincts was sufficient or that our
theories about it were surely sound, yet our notion of what occurs when a
chick grabs a worm are luminous and infallible compared to our notion of
what happens when a kitten runs into the house at the familiar call. The
reason that they have satisfied us as well as they have is just that they
are so vague. We say that the kitten associates the sound ‘kitty kitty’
with the experience of nice milk to drink, which does very well for a
common-sense answer. It also suffices as a rebuke to those who would
have the kitten ratiocinate about the matter, but it fails to tell what
real mental content is present. Does the kitten feel “_sound of call,
memory-image of milk in a saucer in the kitchen, thought of running into
the house, a feeling, finally, of ‘I will run in’_”? Does he perhaps feel
only the sound of the bell and an impulse to run in, similar in quality
to the impulses which make a tennis player run to and fro when playing?
The word ‘association’ may cover a multitude of essentially different
processes, and when a writer attributes anything that an animal may do
to association, his statement has only the negative value of eliminating
reasoning on the one hand and instinct on the other. His position is like
that of a zoölogist who should to-day class an animal among the ‘worms.’
To give to the word a positive value and several definite possibilities
of meaning is one aim of this investigation.

The importance to comparative psychology in general of a more scientific
account of the association-process in animals is evident. Apart from the
desirability of knowing all the facts we can, of whatever sort, there
is the especial consideration that these associations and consequent
habits have an immediate import for biological science. In the higher
animals the bodily life and preservative acts are largely directed by
these associations. They, and not instinct, make the animal use the
best feeding grounds, sleep in the same lair, avoid new dangers and
profit by new changes in nature. Their higher development in mammals
is a chief factor in the supremacy of that group. This, however, is a
minor consideration. The main purpose of the study of the animal mind
is to learn the development of mental life down through the phylum,
to trace in particular the origin of human faculty. In relation to
this chief purpose of comparative psychology the associative processes
assume a rôle predominant over that of sense-powers or instinct, for in
a study of the associative processes lies the solution of the problem.
Sense-powers and instincts have changed by addition and supersedence,
but the cognitive side of consciousness has changed not only in quantity
but also in quality. Somehow out of these associative processes have
arisen human consciousnesses with their sciences and arts and religions.
The association of ideas proper, imagination, memory, abstraction,
generalization, judgment, inference, have here their source. And in the
metamorphosis the instincts, impulses, emotions and sense-impressions
have been transformed out of their old natures. For the origin and
development of human faculty we must look to these processes of
association in lower animals. Not only then does this department need
treatment more, but promises to repay the worker better.

Although no work done in this field is enough like the present
investigation to require an account of its results, the _method_
hitherto in use invites comparison by its contrast and, as I believe,
by its faults. In the first place, most of the books do not give us a
psychology, but rather a _eulogy_, of animals. They have all been about
animal _intelligence_, never about animal _stupidity_. Though a writer
derides the notion that animals have reason, he hastens to add that
they have marvelous capacity of forming associations, and is likely to
refer to the fact that human beings only rarely reason anything out,
that their trains of ideas are ruled mostly by association, as if, in
this latter, animals were on a par with them. The history of books on
animals’ minds thus furnishes an illustration of the well-nigh universal
tendency in human nature to find the marvelous wherever it can. We wonder
that the stars are so big and so far apart, that the microbes are so
small and so thick together, and for much the same reason wonder at the
things animals do. They used to be wonderful because of the mysterious,
God-given faculty of instinct, which could almost remove mountains. More
lately they have been wondered at because of their marvelous mental
powers in profiting by experience. Now imagine an astronomer tremendously
eager to prove the stars as big as possible, or a bacteriologist whose
great scientific desire is to demonstrate the microbes to be very, very
little! Yet there has been a similar eagerness on the part of many
recent writers on animal psychology to praise the abilities of animals.
It cannot help leading to partiality in deductions from facts and more
especially in the choice of facts for investigation. How can scientists
who write like lawyers, defending animals against the charge of having no
power of rationality, be at the same time impartial judges on the bench?
Unfortunately the real work in this field has been done in this spirit.
The level-headed thinkers who might have won valuable results have
contented themselves with arguing against the theories of the eulogists.
They have not made investigations of their own.

In the second place, the facts have generally been derived from
anecdotes. Now quite apart from such pedantry as insists that a man’s
word about a scientific fact is worthless unless he is a trained
scientist, there are really in this field special objections to the
acceptance of the testimony about animals’ intelligent acts which
one gets from anecdotes. Such testimony is by no means on a par with
testimony about the size of a fish or the migration of birds, etc. For
here one has to deal not merely with ignorant or inaccurate testimony,
but also with prejudiced testimony. Human folk are as a matter of fact
eager to find intelligence in animals. They like to. And when the animal
observed is a pet belonging to them or their friends, or when the story
is one that has been told as a story to entertain, further complications
are introduced. Nor is this all. Besides commonly misstating what
facts they report, they report only such facts as show the animal at
his best. Dogs get lost hundreds of times and no one ever notices it
or sends an account of it to a scientific magazine. But let one find
his way from Brooklyn to Yonkers and the fact immediately becomes a
circulating anecdote. Thousands of cats on thousands of occasions sit
helplessly yowling, and no one takes thought of it or writes to his
friend, the professor; but let one cat claw at the knob of a door
supposedly as a signal to be let out, and straightway this cat becomes
the representative of the cat-mind in all the books. The unconscious
distortion of the facts is almost harmless compared to the unconscious
neglect of an animal’s mental life until it verges on the unusual and
marvelous. It is as if some denizen of a planet where communication
was by thought-transference, who was surveying humankind and reporting
their psychology, should be oblivious to all our intercommunication
save such as the psychical-research society has noted. If he should
further misinterpret the cases of mere coincidence of thoughts as facts
comparable to telepathic communication, he would not be more wrong than
some of the animal psychologists. In short, the anecdotes give really the
_abnormal_ or _supernormal_ psychology of animals.

Further, it must be confessed that these vices have been only
ameliorated, not obliterated, when the observation is first-hand, is
made by the psychologist himself. For as men of the utmost scientific
skill have failed to prove good observers in the field of spiritualistic
phenomena,[5] so biologists and psychologists before the pet terrier or
hunted fox often become like Samson shorn. They, too, have looked for the
intelligent and unusual and neglected the stupid and normal.

Finally, in all cases, whether of direct observation or report by good
observers or bad, there have been three other defects. Only a single
case is studied, and so the results are not necessarily true of the
type; the observation is not repeated, nor are the conditions perfectly
regulated; the previous history of the animal in question is not known.
Such observations may tell us, if the observer is perfectly reliable,
that a certain thing takes place; but they cannot assure us that it will
take place universally among the animals of that species, or universally
with the same animal. Nor can the influence of previous experience be
estimated. All this refers to means of getting knowledge about what
animals _do_. The next question is, “What do they _feel_?” Previous work
has not furnished an answer or the material for an answer to this more
important question. Nothing but carefully designed, crucial experiments
can. In abandoning the old method one ought to seek above all to replace
it by one which will not only tell more accurately _what they do_, and
give the much-needed information _how they do it_, but also inform us
_what they feel_ while they act.

To remedy these defects, experiment must be substituted for observation
and the collection of anecdotes. Thus you immediately get rid of several
of them. You can repeat the conditions at will, so as to see whether
or not the animal’s behavior is due to mere coincidence. A number of
animals can be subjected to the same test, so as to attain typical
results. The animal may be put in situations where its conduct is
especially instructive. After considerable preliminary observation of
animals’ behavior under various conditions, I chose for my general method
one which, simple as it is, possesses several other marked advantages
besides those which accompany experiment of any sort. It was merely to
put animals when hungry in inclosures from which they could escape by
some simple act, such as pulling at a loop of cord, pressing a lever,
or stepping on a platform. (A detailed description of these boxes and
pens will be given later.) The animal was put in the inclosure, food was
left outside in sight, and his actions observed. Besides recording his
general behavior, special notice was taken of how he succeeded in doing
the necessary act (in case he did succeed), and a record was kept of the
time that he was in the box before performing the successful pull, or
clawing, or bite. This was repeated until the animal had formed a perfect
association between the sense-impression of the interior of that box and
the impulse leading to the successful movement. When the association
was thus perfect, the time taken to escape was, of course, practically
constant and very short.

If, on the other hand, after a certain time the animal did not succeed,
he was taken out, but _not fed_. If, after a sufficient number of
trials, he failed to get out, the case was recorded as one of complete
failure. Enough different sorts of methods of escape were tried to
make it fairly sure that association in general, not association of a
particular sort of impulse, was being studied. Enough animals were taken
with each box or pen to make it sure that the results were not due to
individual peculiarities. None of the animals used had any previous
acquaintance with any of the mechanical contrivances by which the doors
were opened. So far as possible the animals were kept in a uniform state
of hunger, which was practically utter hunger.[6] That is, no cat or dog
was experimented on, when the experiment involved any important question
of fact or theory, unless I was sure that his motive was of the standard
strength. With chicks this is not practicable, on account of their
delicacy. But with them dislike of loneliness acts as a uniform motive to
get back to the other chicks. Cats (or rather kittens), dogs and chicks
were the subjects of the experiments. All were apparently in excellent
health, save an occasional chick.

By this method of experimentation the animals are put in situations which
call into activity their mental functions and permit them to be carefully
observed. One may, by following it, observe personally more intelligent
acts than are included in any anecdotal collection. And this actual
vision of animals in the act of using their minds is far more fruitful
than any amount of history of what animals have done without the history
of how they did it. But besides affording this opportunity for purposeful
and systematic observation, our method is valuable because it frees the
animal from any influence of the observer. The animal’s behavior is
quite independent of any factors save its own hunger, the mechanism of
the box it is in, the food outside, and such general matters as fatigue,
indisposition, etc. Therefore the work done by one investigator may be
repeated and verified or modified by another. No personal factor is
present save in the observation and interpretation. Again, our method
gives some very important results which are quite uninfluenced by
_any_ personal factor in any way. The curves showing the progress of
the formation of associations, which are obtained from the records of
the times taken by the animal in successive trials, are facts which
may be obtained by any observer who can tell time. They are absolute,
and whatever can be deduced from them is sure. So also the question of
whether an animal does or does not form a certain association requires
for an answer no higher qualification in the observer than a pair of
eyes. The literature of animal psychology shows so uniformly and often so
sadly the influence of the personal equation that any method which can
partially eliminate it deserves a trial.

Furthermore, although the associations formed are such as could not
have been previously experienced or provided for by heredity, they are
still not too remote from the animal’s ordinary course of life. They
mean simply the connection of a certain act with a certain situation
and resultant pleasure, and this general type of association is found
throughout the animal’s life normally. The muscular movements required
are all such as might often be required of the animal. And yet it will
be noted that the acts required are nearly enough like the acts of the
anecdotes to enable one to compare the results of experiment by this
method with the work of the anecdote school. Finally, it may be noticed
that the method lends itself readily to experiments on imitation.

We may now start in with the description of the apparatus and of the
behavior of the animals.[7]

DESCRIPTION OF APPARATUS

[Illustration: FIG. 1.]

The shape and general apparatus of the boxes which were used for the cats
is shown by the accompanying drawing of box K. Unless special figures
are given, it should be understood that each box is approximately 20
inches long, by 15 broad, by 12 high. Except where mention is made to
the contrary, the door was pulled open by a weight attached to a string
which ran over a pulley and was fastened to the door, just as soon as
the animal loosened the bolt or bar which held it. Especial care was
taken not to have the widest openings between the bars at all near the
lever, or wire loop, or what not, which governed the bolt on the door.
For the animal instinctively attacks the large openings first, and if
the mechanism which governs the opening of the door is situated near one
of them, the animal’s task is rendered easier. You do not then get the
association-process so free from the helping hand of instinct as you do
if you make the box without reference to the position of the mechanism to
be set up within it. These various mechanisms are so simple that a verbal
description will suffice in most cases. The facts which the reader should
note are the nature of the movement which the cat had to make, the nature
of the object at which the movement was directed, and the position of the
object in the box. In some special cases attention will also be called
to the force required. In general, however, that was very slight (20 to
100 grams if applied directly). The various boxes will be designated by
capital letters.

A. A string attached to the bolt which held the door ran up over a pulley
on the front edge of the box, and was tied to a wire loop (2½ inches
in diameter) hanging 6 inches above the floor in front center of box.
Clawing or biting it, or rubbing against it even, if in a certain way,
opened the door. We may call this box A ‘_O at front_.’

B. A string attached to the bolt ran up over a pulley on the front edge
of the door, then across the box to another pulley screwed into the
inside of the back of the box 1¼ inches below the top, and passing over
it ended in a wire loop (3 inches in diameter) 6 inches above the floor
in back center of box. Force applied to the loop or _to the string_ as it
ran across the top of the box between two bars would open the door. We
may call B ‘_O at back_.’

B1. In B1 the string ran outside the box, coming down through a hole at
the back, and was therefore inaccessible and invisible from within. Only
by pulling the loop could the door be opened. B1 may be called ‘_O at
back 2d_.’

C. A door of the usual position and size (as in Fig. 1) was kept closed
by a wooden button 3½ inches long, ⅞ inch wide, ½ inch thick. This turned
on a nail driven into the box ½ inch above the middle of the top edge of
the door. The door would fall inward as soon as the button was turned
from its vertical to a horizontal position. A pull of 125 grams would
do this if applied sideways at the lowest point of the button 2¼ inches
below its pivot. The cats usually clawed the button round by downward
pressure on its top edge, which was 1¼ inches above the nail. Then, of
course, more force was necessary. C may be called ‘_Button_.’

D. The door was in the extreme right of the front. A string fastened to
the bolt which held it ran up over a pulley on the top edge and back to
the top edge of the back side of the box (3 inches in from the right
side) and was there firmly fastened. The top of the box was of wire
screening and arched over the string ¾ inch above it along its entire
length. A slight pull on the string anywhere opened the door. This box
was 20 × 16, but a space 7 × 16 was partitioned off at the left by a wire
screen. D may be called ‘_String_.’

D1 was the same box as B, but had the string fastened firmly at the back
instead of running over a pulley and ending in a wire loop. We may call
it ‘_String 2d_.’

E. A string ran from the bolt holding the door up over a pulley and down
to the floor outside the box, where it was fastened 2 inches in front of
the box and 1½ inches to the left of the door (looking from the inside).
By poking a paw out between the bars and pulling this string inward the
door would be opened. We may call E ‘_String outside_.’

In F the string was not fastened to the floor but ended in a loop 2½
inches in diameter which could be clawed down so as to open the door.
Unless the pull was in just the right direction, the string was likely
to catch on the pulley. This loop hung 3 inches above the floor, and 1¾
inches in front of the box. We may call F ‘_String outside unfastened_.’

G was a box 29 × 20½ × 22½, with a door 29 × 12 hinged on the left side
of the box (looking from within), and kept closed by an ordinary thumb
latch placed 15 inches from the floor. The remainder of the front of the
box was closed in by wooden bars. The door was a wooden frame covered
with screening. It was _not_ arranged so as to open as soon as the latch
was lifted, but required a force of 400 grams, even when applied to the
best advantage. The bar of the thumb latch, moreover, would fall back
into place again unless the door were pushed out at least a little. The
top of this box was not of bars or screening, but solid. We may call G
‘_Thumb latch_.’

H was, except for the opening where the door was situated, a perfectly
solid and dark box. In the front was cut an opening about 9 × 7 inches.
A wooden frame covered with wire netting hung in front of this. It was
fastened to the box only by a screw through the middle of the frame’s
top piece, and could therefore be pushed to either side so as to permit
escape from the box if it were prevented from swinging back into place.

I was a box 12 × 14 × 23. The door was 8 inches wide, 4 high, and hinged
at the left side. It was held closed by a wooden bar which moved easily
on a pivot and which could be pushed up by another bar which projected
5 inches into the box. This second bar was pivoted so that downward
pressure on it pushed the first bar up and let the door swing open. The
second bar entered the box at a point 4 inches above the floor and 2½
inches in from the right side of the box. In its normal position its
inner end was 5½ inches above the floor. A depression of 2 inches at that
end was necessary to open the door. Of course, nearer the pivot a shorter
depression would do. The front of the box was closed by bars, but the
rest by solid boards. We may call I ‘_Lever_.’

J was the same as B except that the door was not opened by a weight as
soon as the bolt was pulled up. On the contrary, the door was held closed
by a small piece of board (4 × 3½ × ¾ thick) placed against it outside.
After pulling the loop at the back the cat had to knock down this support
and push the door open. We may call J ‘_Double_.’

K was a box arranged so that three separate acts were required to open
the door, which was held by two bolts at the top and two bars outside.
One of the bolts was connected with a platform in the back center of the
box so that depressing the platform raised the bolt. The other was raised
by a string which ran up over a pulley in the front, across the box 1
inch above the bars, over a pulley near the corner of the box, and down
to the floor, where it was fastened. Pulling on this string, either by
clawing at it where it was running vertically from the last pulley to the
floor, or by putting the paw out between the bars which covered the top
of the box, and clawing the string downward, would raise the bolt. If
both bolts were raised and _either_ bar was pushed up or down far enough
to be out of the way, the cat could escape. K, or ‘_Triple_,’ as it may
be called, is the box reproduced in Figure 1.

L was a box that also required three acts to open the door. It was a
combination of A (O at front), D (string), I (lever). The lever or bar
to be depressed was 2 inches to the right of the door, which was in the
front center. The string to be clawed or bitten ran from front center to
back center 1 inch below the top of the box.

Z was a box with back and sides entirely closed, with front and top
closed by bars and screening, with a small opening in the left-hand
corner. A box was held in front of this and drawn away when the cats
happened to lick themselves. Thus escape and food followed always upon
the impulse to lick themselves, and they soon would immediately start
doing so as soon as pushed into the box. The same box was used with the
impulse changed to that for scratching themselves. The size of this box
was 15 × 10 × 16.

EXPERIMENTS WITH CATS

In these various boxes were put cats from among the following. I give
approximately their ages while under experiment.

No. 1. 8-10 months.
No. 2. 5-7 months.
No. 3. 5-11 months.
No. 4. 5-8 months.
No. 5. 5-7 months.
No. 6. 3-5 months.
No. 7. 3-5 months.
No. 8. 6-6½ months.
No. 10. 4-8 months.
No. 11. 7-8 months.
No. 12. 4-6 months.
No. 13. 18-19 months.

The behavior of all but 11 and 13 was practically the same. When put into
the box the cat would show evident signs of discomfort and of an impulse
to escape from confinement. It tries to squeeze through any opening; it
claws and bites at the bars or wire; it thrusts its paws out through any
opening and claws at everything it reaches; it continues its efforts
when it strikes anything loose and shaky; it may claw at things within
the box. It does not pay very much attention to the food outside, but
seems simply to strive instinctively to escape from confinement. The
vigor with which it struggles is extraordinary. For eight or ten minutes
it will claw and bite and squeeze incessantly. With 13, an old cat, and
11, an uncommonly sluggish cat, the behavior was different. They did not
struggle vigorously or continually. On some occasions they did not even
struggle at all. It was therefore necessary to let them out of some box
a few times, feeding them each time. After they thus associate climbing
out of the box with getting food, they will try to get out whenever put
in. They do not, even then, struggle so vigorously or get so excited
as the rest. In either case, whether the impulse to struggle be due
to an instinctive reaction to confinement or to an association, it is
likely to succeed in letting the cat out of the box. The cat that is
clawing all over the box in her impulsive struggle will probably claw
the string or loop or button so as to open the door. And gradually all
the other non-successful impulses will be stamped out and the particular
impulse leading to the successful act will be stamped in by the resulting
pleasure, until, after many trials, the cat will, when put in the box,
immediately claw the button or loop in a definite way.

The starting point for the formation of any association in these cases,
then, is the set of instinctive activities which are aroused when a cat
feels discomfort in the box either because of confinement or a desire
for food. This discomfort, plus the sense-impression of a surrounding,
confining wall, expresses itself, prior to any experience, in squeezings,
clawings, bitings, etc. From among these movements one is selected by
success. But this is the starting point only in the case of the first
box experienced. After that the cat has associated with the feeling of
confinement certain impulses which have led to success more than others
and are thereby strengthened. A cat that has learned to escape from A by
clawing has, when put into C or G, a greater tendency to claw at things
than it instinctively had at the start, and a less tendency to squeeze
through holes. A very pleasant form of this decrease in instinctive
impulses was noticed in the gradual cessation of howling and mewing.
However, the useless instinctive impulses die out slowly, and often play
an important part even after the cat has had experience with six or eight
boxes. And what is important in our previous statement, namely, that
the activity of an animal when first put into a new box is not directed
by any appreciation of _that_ box’s character, but by certain general
impulses to act, is not affected by this modification. Most of this
activity is determined by heredity; some of it, by previous experience.

My use of the words _instinctive_ and _impulse_ may cause some
misunderstanding unless explained here. Let us, throughout this
book, understand by instinct any reaction which an animal makes to a
situation _without experience_. It thus includes unconscious as well as
conscious acts. Any reaction, then, to totally new phenomena, when first
experienced, will be called instinctive. Any impulse then felt will be
called an instinctive impulse. Instincts include whatever the nervous
system of an animal, as far as inherited, is capable of. My use of the
word will, I hope, everywhere make clear what fact I mean. If the reader
gets the fact meant in mind it does not in the least matter whether he
would himself call such a fact instinct or not. Any one who objects to
the word may substitute ‘hocus-pocus’ for it wherever it occurs. The
definition here made will not be used to prove or disprove any theory,
but simply as a signal for the reader to imagine a certain sort of fact.

The word _impulse_ is used against the writer’s will, but there is no
better. Its meaning will probably become clear as the reader finds it in
actual use, but to avoid misconception at any time I will state now that
_impulse_ means the consciousness accompanying a muscular innervation
_apart from that feeling of the act which comes from seeing oneself
move, from feeling one’s body in a different position, etc._ It is the
_direct feeling of the doing_ as distinguished from the _idea of the
act done_ gained through eye, etc. For this reason I say ‘impulse _and_
act’ instead of simply ‘act.’ Above all, it must be borne in mind that
by impulse I never mean the _motive_ to the act. In popular speech you
may say that hunger is the impulse which makes the cat claw. That will
never be the use here. The word _motive_ will always denote that sort
of consciousness. Any one who thinks that the act ought not to be thus
subdivided into impulse and deed may feel free to use the word _act_ for
_impulse_ or _impulse and act_ throughout, if he will remember that the
act in this aspect of being felt as to be done or as doing is in animals
the important thing, is the thing which gets associated, while the act as
done, as viewed from outside, is a secondary affair. I prefer to have a
separate word, _impulse_, for the former, and keep the word _act_ for the
latter, which it commonly means.

Starting, then, with its store of instinctive impulses, the cat hits
upon the successful movement, and gradually associates it with the
sense-impression of the interior of the box until the connection is
perfect, so that it performs the act as soon as confronted with the
sense-impression. The formation of each association may be represented
graphically by a time-curve. In these curves lengths of one millimeter
along the abscissa represent successive experiences in the box, and
heights of one millimeter above it each represent ten seconds of time.
The curve is formed by joining the tops of perpendiculars erected along
the abscissa 1 mm. apart (the first perpendicular coinciding with the
_y_ line), each perpendicular representing the time the cat was in the
box before escaping. Thus, in Fig. 2 on page 39 the curve marked _12 in
A_ shows that, in 24 experiences or trials in box A, cat 12 took the
following times to perform the act, 160 sec., 30 sec., 90 sec., 60, 15,
28, 20, 30, 22, 11, 15, 20, 12, 10, 14, 10, 8, 8, 5, 10, 8, 6, 6, 7.
A short vertical line below the abscissa denotes that an interval of
approximately 24 hours elapsed before the next trial. Where the interval
was longer it is designated by a figure 2 for two days, 3 for three days,
etc. If the interval was shorter, the number of hours is specified by
1 hr., 2 hrs., etc. In many cases the animal failed in some trial to
perform the act in ten or fifteen minutes and was then taken out by me.
Such failures are denoted by a break in the curve either at its start or
along its course. In some cases there are short curves after the main
ones. These, as shown by the figures beneath, represent the animal’s
mastery of the association after a very long interval of time, and may be
called memory-curves. A discussion of them will come in the last part of
the chapter.

[Illustration: FIG. 2.]

The time-curve is obviously a fair representation of the progress of
the formation of the association, for the two essential factors in the
latter are the disappearance of all activity save the particular sort
which brings success with it, and perfection of that particular sort of
act so that it is done precisely and at will. Of these the second is, on
deeper analysis, found to be a part of the first; any clawing at a loop
except the particular claw which depresses it is theoretically a useless
activity. If we stick to the looser phraseology, however, no harm will
be done. The combination of these two factors is inversely proportional
to the time taken, provided the animal surely wants to get out at once.
This was rendered almost certain by the degree of hunger. Theoretically
a perfect association is formed when both factors are perfect,—when the
animal, for example, does nothing but claw at the loop, and claws at it
in the most useful way for the purpose. In some cases (_e.g._ 2 in K on
page 53) neither factor ever gets perfected in a great many trials. In
some cases the first factor does but the second does not, and the cat
goes at the thing not always in the desirable way. In all cases there is
a fraction of the time which represents getting oneself together after
being dropped in the box, and realizing where one is. But for our purpose
all these matters count little, and we may take the general slope of the
curve as representing very fairly the progress of the association. The
slope of any particular part of it may be due to accident. Thus, very
often the second experience may have a higher time-point than the first,
because the first few successes may all be entirely due to accidentally
hitting the loop, or whatever it is, and whether the accident will
happen sooner in one trial than another is then a matter of chance.
Considering the general slope, it is, of course, apparent that a gradual
descent—say, from initial times of 300 sec. to a constant time of 6 or 8
sec. in the course of 20 to 30 trials—represents a difficult association;
while an abrupt descent, say in 5 trials, from a similar initial height,
represents a very easy association. Thus, 2 in Z, on page 57, is a hard,
and 1 in I, on page 49, an easy association.

[Illustration: FIG. 3.]

In boxes A, C, D, E, I, 100 per cent of the cats given a chance to do so,
hit upon the movement and formed the association. The following table
shows the results where some cats failed:—

TABLE 1

NO. CATS TRIED NO. CATS FAILED
+---------------+---------------+
F | 5 | 4 |
G | 8 | 5 |
H | 9 | 2 |
J | 5 | 2 |
K | 5 | 2 |
+---------------+---------------+

The time-curves follow. By referring to the description of apparatus they
will be easily understood. Each mm. along the abscissa represents one
trial. Each mm. above it represents 10 seconds.

[Illustration: FIG. 4.]

[Illustration: FIG. 5.]

These time-curves show, in the first place, what associations are easy
for an animal to form, and what are hard. The act must be one which the
animal will perform in the course of the activity which its inherited
equipment incites or its previous experience has connected with the
sense-impression of a box’s interior. The oftener the act naturally
occurs in the course of such activity, the sooner it will be performed
in the first trial or so, and this is one condition, sometimes, of the
ease of forming the association. For if the first few successes are five
minutes apart, the influence of one may nearly wear off before the next,
while if they are forty seconds apart the influences may get summated.
But this is not the only or the main condition of the celerity with which
an association may be formed. It depends also on the amount of attention
given to the act. An act of the sort likely to be well attended to will
be learned more quickly. Here, too, accident may play a part, for a cat
may merely happen to be attending to its paw when it claws. The kind of
acts which insure attention are those where the movement which works the
mechanism is one which the cat makes definitely to get out. Thus A (O
at front) is easier to learn than C (button), because the cat does A in
trying to claw down the front of the box and so is attending to what it
does; whereas it does C generally in a vague scramble along the front
or while trying to claw outside with the other paw, and so does not
attend to the little unimportant part of its act which turns the button
round. Above all, _simplicity_ and _definiteness_ in the act make the
association easy. G (thumb latch), J (double) and K and L (triples) are
hard, because complex. E is easy, because directly in the line of the
instinctive impulse to try to pull oneself out of the box by clawing at
anything outside. It is thus very closely attended to. The extreme of
ease is reached when a single experience stamps the association in so
completely that ever after the act is done at once. This is approached in
I and E.

[Illustration: FIG. 6.]

In these experiments the sense-impressions offered no difficulty one more
than the other.

Vigor, abundance of movements, was observed to make differences between
individuals in the same association. It works by shortening the first
times, the times when the cat still does the act largely by accident.
Nos. 3 and 4 show this throughout. Attention, often correlated with lack
of vigor, makes a cat form an association more quickly after he gets
started. No. 13 shows this somewhat. The absence of a fury of activity
let him be more conscious of what he did do.

[Illustration: FIG. 7.]

The curves on pages 57 and 58, showing the history of cats 1, 5, 13 and
3, which were let out of the box Z when they licked themselves, and of
cats 6, 2 and 4, which were let out when they scratched themselves, are
interesting because they show associations where there is no congruity
(no more to a cat than to a man) between the act and the result. One
chick, too, was thus freed whenever he pecked at his feathers to dress
them. He formed the association, and would whirl his head round and poke
it into his feathers as soon as dropped in the box. There is in all these
cases a noticeable tendency, of the cause of which I am ignorant, to
diminish the act until it becomes a mere vestige of a lick or scratch.
After the cat gets so that it performs the act soon after being put in,
it begins to do it less and less vigorously. The licking degenerates into
a mere quick turn of the head with one or two motions up and down with
tongue extended. Instead of a hearty scratch, the cat waves its paw up
and down rapidly for an instant. Moreover, if sometimes you do not let
the cat out after this feeble reaction, it does not at once repeat the
movement, as it would do if it depressed a thumb piece, for instance,
without success in getting the door open. Of the reason for this
difference I am again ignorant.

Previous experience makes a difference in the quickness with which the
cat forms the associations. After getting out of six or eight boxes by
different sorts of acts the cat’s general tendency to claw at loose
objects within the box is strengthened and its tendency to squeeze
through holes and bite bars is weakened; accordingly it will learn
associations along the general line of the old more quickly. Further,
its tendency to pay attention to what it is doing gets strengthened,
and this is something which may properly be called a change in degree
of intelligence. A test was made of the influence of experience in this
latter way by putting two groups of cats through I (lever), one group (1,
2, 3, 4, 5) after considerable experience, the other (10, 11, 12) after
experience with only one box. As the act in I was not along the line
of the acts in previous boxes, and as a decrease in the squeezings and
bitings would be of little use in the box as arranged, the influence of
experience in the former way was of little account. The curves of all are
shown on page 49.

[Illustration: FIG. 8.]

If the whole set of curves are examined in connection with the following
table, which gives the general order in which each animal took up the
different associations which he eventually formed, many suggestions
of the influence of experience will be met with. The results are not
exhaustive enough to justify more than the general conclusion that there
is such an influence. By taking more individuals and thus eliminating all
other factors besides experience, one can easily show just how and how
far experience facilitates association.

When, in this table, the letters designating the boxes are in italics it
means that, though the cat formed the association, it was in connection
with other experiments and so is not recorded in the curves.

TABLE 2

+------+-------------------------------+
|Cat 1 | _A_ _B_ _C_ _D₁_ _D_ Z I |
|Cat 2 | _C_ _D₁_ _D_ E Z H J I K |
|Cat 3 | A C E G H J Z I K |
|Cat 4 | C F G D Z H J I K |
|Cat 5 | C E Z H I |
|Cat 6 | _A_ _C_ E Z |
|Cat 7 | _A_ _C_ |
|Cat 10| C I A H D L |
|Cat 11| C I A H D L |
|Cat 12| C I A H D L |
|Cat 13| A C D G Z |
+------+-------------------------------+

[Illustration: FIG. 9.]

The advantage due to experience in our experiments is not, however,
the same as ordinarily in the case of trained animals. With them the
associations are with the acts or voice of man or with sense-impressions
to which they naturally do not attend (_e.g._ figures on a blackboard,
ringing of a bell, some act of another animal). Here the advantage of
experience is mainly due to the fact that by such experience the animals
gain the habit of attending to the master’s face and voice and acts and
to sense-impressions in general.

I made no attempt to find the differences in ability to acquire
associations due to age or sex or fatigue or circumstances of any
sort. By simply finding the average slope in the different cases to be
compared, one can easily demonstrate any such differences that exist. So
far as this discovery is profitable, investigation along this line ought
now to go on without delay, the method being made clear. Of differences
due to differences in the species, genus, etc., of the animals I will
speak after reviewing the time-curves of dogs and chicks.

In the present state of animal psychology there is another value to
these results which was especially aimed at by the investigator from the
start. They furnish a quantitative estimate of what the average cat can
do, so that if any one has an animal which he thinks has shown superior
intelligence or perhaps reasoning power, he may test his observations and
opinion by taking the time-curves of the animal in such boxes as I have
described.

[Illustration: FIG. 10.]

If his animal in a number of cases forms the associations very much more
quickly, or deals with the situation in a more intelligent fashion than
my cats did, then he may have ground for claiming in his individual a
variation toward greater intelligence and, possibly, intelligence of a
different order. On the other hand, if the animal fails to rise above the
type in his dealings with the boxes, the observer should confess that his
opinion of the animal’s intelligence may have been at fault and should
look for a correction of it.

We have in these time-curves a fairly adequate measure of what the
ordinary cat can do, and how it does it, and in similar curves soon to
be presented a less adequate measure of what a dog may do. If other
investigators, especially all amateurs who are interested in animal
intelligence, will take other cats and dogs, especially those supposed
by owners to be extraordinarily intelligent, and experiment with them in
this way, we shall soon get a notion of how much variation there is among
animals in the direction of more or superior intelligence. The beginning
here made is meager but solid. The knowledge it gives needs to be much
extended. The variations found in individuals should be correlated, not
merely with supposed superiority in intelligence, a factor too vague to
be very serviceable, but with observed differences in vigor, attention,
memory and muscular skill. No phenomena are more capable of exact and
thorough investigation by experiment than the associations of animal
consciousness. Never will you get a better psychological subject than a
hungry cat. When the crude beginnings of this research have been improved
and replaced by more ingenious and adroit experimenters, the results
ought to be very valuable.

Surely every one must agree that no man now has a right to advance
theories about what is in animals’ minds or to deny previous theories
unless he supports his thesis by systematic and extended experiments. My
own theories, soon to be proclaimed, will doubtless be opposed by many.
I sincerely hope they will, provided the denial is accompanied by actual
experimental work. In fact, I shall be tempted again and again in the
course of this book to defend some theory, dubious enough to my own mind,
in the hope of thereby inducing some one to oppose me and in opposing me
to make the experiments I have myself had no opportunity to make yet.
Probably there will be enough opposition if I confine myself to the
theories I feel sure of.

[Illustration: FIG. 11.]

EXPERIMENTS WITH DOGS

The boxes used were as follows:

AA was similar to A (O at front), except that the loop was of stiff cord
⅜ inch in diameter and was larger (3½ inches diameter); also it was hung
a foot from the floor and 8 inches to the right of the door. The box
itself was 41 × 20 × 23.

BB was similar to B, the loop being the same as in AA, and being hung a
foot from the floor. The box was of the same size and shape as AA.

BB1 was like BB, but the loop was hung 18 inches from the floor.

CC was similar to C (button), but the button was 6 inches long, and the
box was 36½ × 22 × 23.

II was similar to I, but the box was 30 × 20 × 25 inches; the door (11
inches wide, 6 high) was in the left front corner, and the lever was 6
inches long and entered the box at a point 2 inches to the right of the
door and 4 inches above the floor.

[Illustration: FIG. 12.]

In M the same box as in II was used, but instead of a lever projecting
inside the box, a lever running outside parallel to the plane of the
front of the box and 18 inches long was used. This lay close against the
bars composing the front of the box, and could be pawed down by sticking
the paw out an inch or so between two bars, at a point about 15 inches
high and 6 inches in from the right edge of the front. We may call M
‘_Lever outside_.’

[Illustration: FIG. 13.]

N was a pen 5 × 3 feet made of wire netting 46 inches high. The door, 31
× 20, was in the right half of the front. A string from the bolt passed
up over a pulley and back to the back center, where it was fastened 33
inches above the floor. Biting or pawing this string opened the door.

O was like K, except that there was only one bar, that the string ran
inside the box, so that it was easily accessible, and that the bolt
raised in K by depression of the platform could be raised in O (and was
by the dog experimented on) by sticking the muzzle out between two bars
just above the bolt and by biting the string, at the same time jerking it
upward. O was 30 × 20 × 25 in size.

The box G was used for both dogs and cats, without any variation save
that for dogs the resistance of the door to pressure outwards was doubled.

In these boxes were put in the course of the experiments dog 1 (about 8
months old), and dogs 2 and 3, adults, all of small size.

A dog who, when hungry, is shut up in one of these boxes is not nearly
so vigorous in his struggles to get out as is the young cat. And even
after he has experienced the pleasure of eating on escape many times he
does not try to get out so hard as a cat, young or old. He does try to
a certain extent. He paws or bites the bars or screening, and tries to
squeeze out in a tame sort of way. He gives up his attempts sooner than
the cat, if they prove unsuccessful. Furthermore his attention is taken
by the food, not the confinement. He wants to get _to_ the food, not _out
of_ the box. So, unlike the cat, he confines his efforts to the front
of the box. It was also a practical necessity that the dogs should be
kept from howling in the evening, and for this reason I could not use
as motive the utter hunger which the cats were made to suffer. In the
morning, when the experiments were made, the dogs were surely hungry,
and no experiment is recorded in which the dog was not in a state to be
willing to make a great effort for a bit of meat, but the motive may not
have been even and equal throughout, as it was with the cats.

[Illustration: FIG. 14.]

The curves on page 60 are to be interpreted in the same way as those for
the cats, and are on the same scale. The order in which No. 1 took up the
various associations was AA, BB, BB1, G, N, CC, II, O.

The percentage of dogs succeeding in the various boxes is given below,
but is of no consequence, because so few were tried, and because the
motive, hunger, was not perhaps strong enough, or equal in all cases.

In AA 3 out of 3.

In BB 0 out of 2 (that is, without previous experience of AA).

In CC 1 out of 2.

In II 3 out of 3.

In M 1 out of 2.

In N 1 out of 3.

In G 1 out of 3.

EXPERIMENTS WITH CHICKS

The apparatus was as follows:

[Illustration: FIG. 15. FIG. 16. FIG. 17.]

P was simply a small pen arranged with two exits, one leading to the
inclosure where were the other chicks and food, one leading to another
pen with no exit. The drawing (Fig. 15 on this page) explains itself. A
chick was placed at A and left to find its way out. The walls were made
of books stuck up on end.

Q was a similar pen arranged so that the real exit was harder to find.
(See Fig. 16.)

R was still another pen similarly constructed, with four possible avenues
to be taken. (See Fig. 17.)

S was a pen with walls 11 inches high. On the right side an inclined
plane of wire screening led from the floor of the pen to the top of its
front wall. Thence the chick could jump down to where its fellows and the
food and drink were. S was 17 × 14 in size.

T was a pen of the same size as S, with a block of wood 3 inches by 3
and 2 inches high in the right back corner. From this an inclined plane
led to the top of the front wall (on the right side of the box). But a
partition was placed along the left edge of this plane, so that a chick
could reach it only _via_ the wooden block, not by a direct jump.

U was a pen 16 × 14 × 10 inches. Along the back toward the right corner
were placed a series of steps 1½ inches wide, the first 1, the second
2, and the third 3 inches high. In the corner was a platform 4 × 4, and
4 high, from which access to the top of the front wall of the pen could
be gained by scrambling up inside a stovepipe 11 inches long, inclined
upward at an angle of about 30°. From the edge of the wall the chick
could, of course, jump down to food and society. The top of the pen was
covered so that the chick could not from the platform jump onto the edge
of the stovepipe or the top of the pen wall. The only means of exit was
to go up the steps to the platform, up through the stovepipe to the front
wall, and then jump down.

The time-curves for chicks 90, 91, 92, 93, 94 and 95, all 2-8 days old
when experimented on, follow on page 65. The scale is the same as that
in the curves of the cats and dogs. Besides these simple acts, which any
average chick will accidentally hit upon and associate, there are, in
the records of my preliminary study of animal intelligence, a multitude
of all sorts of associations which some chicks have happened to form.
Chicks have escaped from confinement by stepping on a little platform in
the back of the box, by jumping up and pulling a string like that in D,
by pecking at a door, by climbing up a spiral staircase and out through
a hole in the wall, by doing this and then in addition walking across a
ladder for a foot to another wall from which they jump down, etc. Not
every chick will happen upon the right way in these cases, but the chicks
who did happen upon it all formed the associations perfectly after enough
trials.

The behavior of the chicks shows the same general character as that
of the cats, conditioned, of course, by the different nature of the
instinctive impulses. Take a chick put in T (inclined plane) for an
example. When taken from the food and other chicks and dropped into the
pen he shows evident signs of discomfort; he runs back and forth, peeping
loudly, trying to squeeze through any openings there may be, jumping up
to get over the wall, and pecking at the bars or screen, if such separate
him from the other chicks. Finally, in his general running around he goes
up the inclined plane a way. He may come down again, or he may go on up
far enough to see over the top of the wall. If he does, he will probably
go running up the rest of the way and jump down. With further trials he
gains more and more of an impulse to walk up an inclined plane when he
sees it, while the vain running and pecking, etc., are stamped out by the
absence of any sequent pleasure. Finally, the chick goes up the plane as
soon as put in. In scientific terms this history means that the chick,
when confronted by loneliness and confining walls, responds by those acts
which in similar conditions in nature would be likely to free him. Some
one of these acts leads him to the successful act, and the resulting
pleasure stamps it in. Absence of pleasure stamps all others out. The
case is just the same as with dogs and cats. The time-curves are shown in
Fig. 18.

Coming now to the question of differences in intelligence between
the different animals, it is clear that such differences are hard to
estimate accurately. The chicks are surely very much slower in forming
associations and less able to tackle hard ones, but the biggest part of
the difference between what they do and what the dogs and cats do is not
referable so much to any difference in intelligence as to a difference
in their bodily organs and instinctive impulses. As between dogs and
cats, the influence of the difference in quantity of activity, in the
direction of the instinctive impulses, in the versatility of the fore
limb, is hard to separate from the influence of intelligence proper.
The best practical tests to judge such differences in general would be
differences in memory, which are very easily got at, differences in the
delicacy and complexity attainable, and, of course, differences in the
slope of the curves for the same association. If all these tests agreed,
we should have a right to rank one animal above the other in a scale
of intelligence. But this whole question of grading is, after all, not
so important for comparative psychology as its popularity could lead
one to think. Comparative psychology wants first of all to trace human
intellection back through the phylum to its origin, and in this aim is
helped little by knowing that dogs are brighter than cats, or whales than
seals, or horses than cows. Further, the whole question of ‘intelligence’
should be resolved into particular inquiries into the development of
attention, activity, memory, etc.

[Illustration: FIG. 18.]

So far as concerns dogs and cats, I should decide that the former were
more generally intelligent. The main reason, however, why dogs seem to us
so intelligent is not a good reason for the belief. It is because, more
than any other domestic animal, they direct their attention to _us_, to
what we do, and so form associations connected with acts of ours.

Having finished our attempt to give a true description of the facts of
association, so far as observed from the outside, we may now progress to
discuss its inner nature. A little preface about certain verbal usages is
necessary before doing so. Throughout I shall use the word ‘animal’ or
‘animals,’ and the reader might fancy that I took it for granted that the
associative processes were the same in all animals as in these cats and
dogs of mine. Really, I claim for my animal psychology only that it is
the psychology of just these particular animals. What this warrants about
animals in general may be left largely to the discretion of the reader.
As I shall later say, it is probable that in regard to imitation and the
power of forming associations from a lot of free ideas, the anthropoid
primates are essentially different from the cats and dogs.

The reasons why I say ‘animals’ instead of ‘dogs and cats of certain
ages’ are two. I do think that the probability that the other mammals,
barring the primates, offer no objections to the theories here advanced
about dogs and cats is a very strong probability, strong enough to force
the burden of proof upon any one who should, for instance, say that
horse-goat psychology was not like cat-dog psychology in these general
matters. I should claim that, till the contrary was shown in any case,
my statements should stand for the mammalian mind in general, barring
the primates. My second reason is that I hate to burden the reader
with the disgusting rhetoric which would result if I had to insert
particularizations and reservations at every step. The word ‘animal’ is
too useful, rhetorically, to be sacrificed. Finally, inasmuch as most
of my theorizing will be in the line of denying certain relatively high
functions to animals, the evidence from cats and dogs is sufficient, for
they are from among the most intelligent animals, and functions of the
kind to be discussed, if absent in their case, are probably absent from
the others.

REASONING OR INFERENCE

The first great question is whether or not animals are ever led to do
any of their acts by reasoning. Do they ever conclude from inference
that a certain act will produce a certain desired result, and so do it?
The best opinion has been that they do not. The best interpretation of
even the most extraordinary performances of animals has been that they
were the result of accident and association or imitation. But it has
after all been only opinion and interpretation, and the opposite theory
persistently reappears in the literature of the subject. So, although
it is in a way superfluous to give the _coup de grâce_ to the despised
theory that animals reason, I think it is worth while to settle this
question once for all.

The great support of those who do claim for animals the ability to infer
has been their wonderful performances which resemble our own. These could
not, they claim, have happened by accident. No animal could learn to open
a latched gate by accident. The whole substance of the argument vanishes
if, as a matter of fact, animals do learn those things by accident.
_They certainly do._ In this investigation choice was made of the
intelligent performances described by Romanes in the following passages.
I shall quote at some length because these passages give an admirable
illustration of an attitude of investigation which this research will, I
hope, render impossible for any scientist in the future. Speaking of the
general intelligence of cats, Romanes says:

“Thus, for instance, while I have only heard of one solitary
case ... of a dog which, without tuition, divined the use of
a thumb latch so as to open a closed door by jumping on the
handle and depressing the thumb-piece, I have received some
half-dozen instances of this display of intelligence on the
part of cats. These instances are all such precise repetitions
of one another that I conclude the fact to be one of tolerably
ordinary occurrence among cats, while it is certainly rare
among dogs. I may add that my own coachman once had a cat
which, certainly without tuition, learnt thus to open a door
that led into the stables from a yard into which looked some
of the windows of the house. Standing at these windows when
the cat did not see me, I have many times witnessed her _modus
operandi_. Walking up to the door with a most matter-of-course
kind of air, she used to spring at the half hoop handle just
below the thumb latch. Holding on to the bottom of this
half-hoop with one fore paw, she then raised the other to the
thumb piece, and while depressing the latter finally with her
hind legs scratched and pushed the door posts so as to open the
door....

“Of course in all such cases the cats must have previously
observed that the doors are opened by persons placing their
hands upon the handles and, having observed this, the animals
act by what may be strictly termed rational imitation. But it
should be observed that the process as a whole is something
more than imitative. For not only would observation alone be
scarcely enough (within any limits of thoughtful reflection
that it would be reasonable to ascribe to an animal) to enable
a cat upon the ground to distinguish that the essential part
of the process consists not in grasping the handle, but in
depressing the latch; but the cat certainly never saw any one,
after having depressed the latch, pushing the door posts with
his legs; and that this pushing action is due to an originally
deliberate intention of opening the door, and not to having
accidentally found this action to assist the process, is shown
by one of the cases communicated to me; for in this case, my
correspondent says, ‘the door was not a loose-fitting one, by
any means, and I was surprised that by the force of one hind
leg she should have been able to push it open after unlatching
it.’ Hence we can only conclude that the cats in such cases
have a very definite idea as to the mechanical properties of
a door: they know that to make it open, even when unlatched,
it requires to be _pushed_—a very different thing from trying
to imitate any particular action which they may see to be
performed for the same purpose by man. The whole psychological
process, therefore, implied by the fact of a cat opening a
door in this way is really most complex. First the animal must
have observed that the door is opened by the hand grasping
the handle and moving the latch. Next she must reason, by
‘the logic of feelings’—‘If a hand can do it, why not a paw?’
Then strongly moved by this idea she makes the first trial.
The steps which follow have not been observed, so we cannot
certainly say whether she learns by a succession of trials that
depression of the thumb piece constitutes the essential part
of the process, or, perhaps more probably, that her initial
observations supplied her with the idea of clicking the thumb
piece. But, however this may be, it is certain that the pushing
with the hind feet after depressing the latch must be due to
adaptive reasoning unassisted by observation; and only by the
concerted action of all her limbs in the performance of a
highly complex and most unnatural movement is her final purpose
attained.” (Animal Intelligence, pp. 420-422.)

A page or two later we find a less ponderous account of a cat’s success
in turning aside a button and so opening a window:—

“At Parara, the residence of Parker Bowman, Esq., a full-grown
cat was one day accidentally locked up in a room without any
other outlet than a small window, moving on hinges, and kept
shut by means of a swivel. Not long afterwards the window was
found open and the cat gone. This having happened several
times, it was at last found that the cat jumped upon the window
sill, placed her fore paws as high as she could reach against
the side, deliberately reached with one over to the swivel,
moved it from its horizontal to a vertical position, and then,
leaning with her whole weight against the window, swung it open
and escaped.” (Animal Intelligence, p. 425.)

A description has already been given on page 31 of the small box (C),
whose door fell open when the button was turned, and also of a large
box (CC) for the dogs, with a similar door. The thumb-latch experiment
was carried on with the same box (G) for both cats and dogs, but the
door was arranged so that a greater force (1.3 kilograms) was required
in the case of the dogs. It will be remembered that the latch was so
fixed that if the thumb piece were pressed down, without contemporaneous
outward pressure of the door, the latch bar would merely drop back into
its catch as soon as the paw was taken off the door. If, however, the
door were pushed outward, the latch bar, being pressed closely against
the outer edge of its catch, would, if lifted, be likely to fall outside
it and so permit the door to open if then or later sufficient pressure
were exerted. Eight cats (Nos. 1, 2, 3, 4, 5, 6, 7 and 13) were, one
at a time, left in this thumb-latch box. All exhibited the customary
instinctive clawings and squeezings and bitings. Out of the eight all
succeeded in the course of their vigorous struggles in pressing down
the thumb piece, so that if the door had been free to swing open, they
could have escaped. Six succeeded in pushing both thumb-piece down and
door out, so that the bar did not fall back into its place. Of these five
succeeded in also later pushing the door open, so that they escaped and
got the fish outside. Of these, three, after repeated trials, associated
the complicated movements required with the sight of the interior of the
box so firmly that they attacked the thumb latch the moment they were put
in. The history of the formation of the association in the case of 3 and
of 4 is shown in the curves in Figs. 6 and 7. In the case of 13 the exact
times were not taken. The combination of accidents required was enough to
make No. 1 and No. 6 take a long time to get out. Consequently, weariness
and failure inhibited their impulses to claw, climb, etc., more than the
rare pleasure from getting out strengthened them, and they failed to
form the association. Like the cats who utterly failed to get out, they
finally ceased to try when put in. The history of their efforts is as in
Table 3: the figures in the columns represent the time (in minutes and
seconds) the animal was in the box before escaping or before being taken
out if he failed to escape. Cases of failure are designated by an F after
the figures. Double lines represent an interval of twenty-four hours.

TABLE 3

+----------+---------+
| No. 1. | No. 6. |
+==========+=========+
| 13.00 F | 17.50 |
| 9.30 | 3.30 |
| 1.40 | 9.00 |
| .50 | 2.10 |
| 15.00 | 1.45 |
| 6.00 F | 1.55 |
+==========+ |
| 14.00 | 13.00 |
| +=========+
| 20.00 F | 5.00 |
| 4.30 | 2.30 |
| 20.00 F | 15.00 |
| 20.00 F | 10.00 F |
| +=========+
| 15.00 F | 5.00 |
+==========+ |
| 60.00 F | 15.00 F |
| +=========+
| | 10.00 F |
| +=========+
| | 10.00 F |
+----------+---------+

It should be noted that, although cats 3 and 4 had had some experience
in getting out of boxes by clawing at loops and turning buttons, they
had never had anything at all like a thumb latch to claw at, nor had
they ever seen the door opened by its use, nor did they even have any
experience of the fact that the part of the box where the thumb piece
was was the door. And we may insert here, what will be stated more fully
later, that there was displayed no observation of the surroundings or
deliberation upon them. It was just a mad scramble to get out.

Three dogs (1, 2 and 3) were given a chance to liberate themselves from
this same box. 2 and 3, who were rather inactive, failed to even push the
thumb piece down. No. 1, who was very active, did push it down at the
same time that she happened to be pushing against the door. She repeated
this and formed the association as shown in the curve on page 60. She had
had experience only of escaping by pulling a loop of string.

Out of 6 cats who were put in the box whose door opened by a button,
not one failed, in the course of its impulsive activity, to push the
button around. Sometimes it was clawed to one side from below; sometimes
vigorous pressure on the top turned it around; sometimes it was pushed
up by the nose. No cat who was given repeated trials failed to form a
perfect association between the sight of the interior of that box and
the proper movements. Some of these cats had been in other boxes where
pulling a loop of string liberated them, 3 and 4 had had considerable
experience with the boxes and probably had acquired a general tendency to
claw at loose objects. 10, 11 and 12 had never been in _any box_ before.
The curves are on pages 41 and 43.

Of two dogs, one, when placed in a similar but larger box, succeeded in
hitting the button in such a way as to let the door open, and formed
a permanent association, as shown by the curves on page 41. No one who
had seen the behavior of these animals when trying to escape could doubt
that their actions were directed by instinctive impulses, not by rational
observation. It is then absolutely sure that a dog or cat _can_ open a
door closed by a thumb latch or button, merely by the accidental success
of its natural impulses. If _all_ cats, when hungry and in a _small_ box,
will accidentally push the button that holds the door, an _occasional_
cat in a _large_ room may very well do the same. If three cats out of
eight will accidentally press down a thumb piece and push open a small
door, three cats out of a thousand may very well open doors or gates in
the same way.

But besides thus depriving of their value the facts which these
theorizers offer as evidence, we may, by a careful examination of
the method of formation of these associations as it is shown in the
time-curves, gain positive evidence that no power of inference was
present in the subjects of the experiments. Surely if 1 and 6 had
possessed any power of inference, they would not have failed to get
out after having done so several times. Yet they did. (See p. 71.) If
they had once even, much less if they had six or eight times, inferred
what was to be done, they should have made the inference the seventh or
ninth time. And if there were in these animals any power of inference,
however rudimentary, however sporadic, however dim, there should have
appeared among the multitude some cases where an animal, seeing through
the situation, knows the proper act, does it, and from then on does
it immediately upon being confronted with the situation. There ought,
that is, to be a sudden vertical descent in the time-curve. Of course,
where the act resulting from the impulse is very simple, very obvious,
and very clearly defined, a single experience may make the association
perfect, and we may have an abrupt descent in the time-curve without
needing to suppose inference. But if in a complex act, a series of
acts or an ill-defined act, one found such a sudden consummation in
the associative process, one might very well claim that reason was at
work. Now, the scores of cases recorded show no such phenomena. The
cat does not look over the situation, much less _think_ it over, and
then decide what to do. It bursts out at once into the activities which
instinct and experience have settled on as suitable reactions to the
situation ‘_confinement when hungry with food outside_.’ It does not
ever in the course of its successes realize that such an act brings
food and therefore decide to do it and thenceforth do it immediately
from _decision_ instead of from impulse. The one impulse, out of
many accidental ones, which leads to pleasure, becomes strengthened
and stamped in thereby, and more and more firmly associated with the
sense-impression of that box’s interior. Accordingly it is sooner and
sooner fulfilled. Futile impulses are gradually stamped out. The gradual
slope of the time-curve, then, shows the absence of reasoning. They
represent the wearing smooth of a path in the brain, not the decisions of
a rational consciousness.

In a later discussion of imitation further evidence that animals do not
reason will appear. For the present, suffice it to say, that a dog, or
cat, or chick, who does not in his own impulsive activity learn to escape
from a box by pulling the proper loop, or stepping on a platform, or
pecking at a door, will not learn it from seeing his fellows do so. They
are incapable of even the inference (if the process may be dignified by
that name) that what gives another food will give it to them also. So,
also, it will be later seen that an animal cannot learn an act by being
put through it. For instance, a cat who fails to push down a thumb piece
and push out the door cannot be taught by having one take its paw and
press the thumb piece down with it. This _could_ be learned by a certain
type of associative process without inference. _Were there inference, it
surely would be learned._

Finally, attention may be called to the curves which show the way that
the animal mind deals with a series of acts (_e.g._ curves for G, J, K,
L and O, found on pages 45 to 55 and 60). Were there any reasoning the
animals ought early to master the method of escape in these cases (see
descriptions on pages 31 to 34) so as to do the several acts in order,
and not to repeat one after doing it once, or else ought utterly to fail
to master the thing. But, in all these experiments, where there was every
motive for the use of any reasoning faculty, if such existed, where the
animals literally lived by their intellectual powers, one finds no sign
of abstraction, or inference, or judgment.

So far I have only given facts which are quite uninfluenced by any
possible incompetence or prejudice of the observer. These alone seem
to disprove the existence of any rational faculty in the subjects
experimented on. I may add that my observations of all the conduct of all
these animals during the months spent with them, failed to find any act
that even _seemed_ due to reasoning. I should claim that this quarrel
ought now to be dropped for good and all,—that investigation ought to
be directed along more sensible and profitable lines. I should claim
that the psychologist who studies dogs and cats in order to defend this
‘reason’ theory is on a level with a zoölogist who should study fishes
with a view to supporting the thesis that they possessed clawed digits.
The rest of this account will deal with more promising problems, of
which the first, and not the least important, concerns the facts and
theories of _imitation_.

IMITATION

To the question, ‘Do animals imitate?’ science has uniformly answered,
‘Yes.’ But so long as the question is left in this general form, no
correct answer to it is possible. It will be seen, from the results
of numerous experiments soon to be described, that imitation of a
certain sort is not possible for animals, and before entering upon that
description it will be helpful to differentiate this matter of imitation
into several varieties or aspects. The presence of some sorts of
imitation does not imply that of other sorts.

There are, to begin with, the well-known phenomena presented by the
imitative birds. The power is extended widely, ranging from the parrot
who knows a hundred or more articulate sounds to the sparrow whom a
patient shoemaker taught to get through a tune. Now, if a bird really
gets a sound in his mind from hearing it and sets out forthwith to
imitate it, as mocking birds are said at times to do, it is a mystery and
deserves closest study. If a bird, out of a lot of random noises that it
makes, chooses those for repetition which are like sounds that he has
heard, it is again a mystery _why_, though not as in the previous case a
mystery _how_, he does it. The important fact for our purpose is that,
though the imitation of sounds is so habitual, there does not appear to
be any marked general imitative tendency in these birds. There is no
proof that parrots do muscular acts from having seen other parrots do
them. But this should be studied. At any rate, until we know what sort of
sounds birds imitate, what circumstances or emotional attitudes these
are connected with, how they learn them and, above all, whether there is
in birds which repeat sounds any tendency to imitate in other lines, we
cannot, it seems to me, connect these phenomena with anything found in
the mammals or use them to advantage in a discussion of animal imitation
as the forerunner of human. In what follows they will be left out of
account, will be regarded as a specialization removed from the general
course of mental development, just as the feathers or right aortic
arch of birds are particular specializations of no consequence for the
physical development of mammals. For us, henceforth, imitation will mean
imitation minus the phenomena of imitative birds.

There are also certain pseudo-imitative or semi-imitative phenomena which
ought to be considered by themselves. For example, the rapid loss of
the fear of railroad trains or telegraph wires among birds, the rapid
acquisition of arboreal habits among Australian rodents, the use of
proper feeding grounds, etc., may be held to be due to imitation. The
young animal stays with or follows its mother from a specific instinct to
keep near that particular object, to wit, its mother. It may thus learn
to stay near trains, or scramble up trees, or feed at certain places and
on certain plants. Actions due to following pure and simple may thus
simulate imitation. Other groups of acts which now seem truly imitative
may be indirect fruits of some one instinct. This must be kept in mind
when one estimates the supposed imitation of parents by young. Further,
it is certain that in the case of the chick, where early animal life has
been carefully observed, instinct and individual experience between them
rob imitation of practically all its supposed influence. Chicks get along
without a mother very well. Yet no mother takes more care of her children
than the hen. Care in other cases, then, need not mean instruction
through imitation.

These considerations may prevent an unreserved acceptance of the common
view that young animals get a great number of their useful habits from
imitation, but I do not expect or desire them to lead to its summary
rejection. I should not now myself reject it, though I think it quite
possible that more investigation and experiment may finally reduce all
the phenomena of so-called imitation of parents by young to the level of
indirect results of instinctive acts.

Another special department of imitation may be at least vaguely marked
off: namely, apparent imitation of certain limited sorts of acts which
are somewhat frequent in the animal’s life. An example will do better
than further definition.

Some sheep were being driven on board ship one at a time. In the course
of their progress they had to jump over a hurdle. On this being removed
before all had passed it, the next sheep was seen to jump as if to get
over a hurdle, and so on for five or six, apparently sure evidence that
they imitated the action, each of the one in front. Now, it is again
possible that among gregarious animals there may be elaborate connections
in the nervous system which allow the sight of certain particular acts in
another animal to arouse the innervation leading to those acts, but that
these connections are _limited_. The reactions on this view are specific
responses to definite signals, comparable to any other instinctive or
associational reaction. The sheep jumps when he sees the other sheep
jump, not because of a general ability to do what he sees done, but
because he is furnished with the instinct to jump at such a sight, or
because his experience of following the flock over boulders and brooks
and walls has got him into the habit of jumping at the spot where he
sees one ahead of him jump; and so he jumps even though no obstacle be
in his way. If due to instinct, the only peculiarity of such a reaction
would be that the sense-impression calling forth the act would be the
same act as done by another. If due to experience, there would be an
exact correspondence to the frequent acts called forth _originally_ by
several elements in a sense-impression, one of which is essential, and
done _afterwards_ when only the _non-essentials_ are present. These two
possibilities have not been sufficiently realized, yet they may contain
the truth. On the other hand, these limited acts may be the primitive,
sporadic beginnings of the general imitative faculty which we find in
man. To this general faculty we may now turn, having cleared away some of
the more doubtful phenomena which have shared its name.

It should be kept in mind that an imitative act may be performed quite
unthinkingly, as when a man in the mob shouts what the others shout or
claps when the others clap; may be done from an inference that since A
by doing X makes pleasure for himself, I by doing X may get pleasure
for myself; may, lastly, be done from what may be called a transferred
association. This process is the one of interest in connection with our
general topic, and most of my experiments on imitation were directed to
the investigation of it. Its nature is simple. One sees the following
sequence: ‘A turning a faucet, A getting a drink.’ If one can free this
association from its narrow confinement to A, so as to get from it the
association, ‘impulse to turn faucet, _me_ getting a drink,’ one will
surely, if thirsty, turn the faucet, though he had never done so before.
If one can from an act witnessed learn to do the act, he in some way
makes use of the sequence seen, transfers the process to himself; in the
common human sense of the word, he _imitates_. This kind of imitation
is surely common in human life. It may be apparent in ontogeny before
any power of inference is shown. After that power does appear, it still
retains a wide scope, and teaches us a majority, perhaps, of the ordinary
accomplishments of our practical life.

Now, as the writers of books about animal intelligence have not
differentiated this meaning from the other possible ones, it is
impossible to say surely that they have uniformly credited it to animals,
and it is profitless to catalogue here their vague statements. Many
opposers of the ‘reason’ theory have presupposed such a process and used
it to replace reason as the cause of some intelligent performances. The
upholders of the reason theory have customarily recognized such a process
and claimed to have discounted it in their explanations of the various
anecdotes. So we found Mr. Romanes, in the passage quoted, discussing the
possibility that such an imitative process, without reason, could account
for the facts. In his chapter on Imitation in ‘Habit and Instinct,’
Principal C. Lloyd Morgan, the sanest writer on comparative psychology,
seems to accept imitation of this sort as a fact, though he could, if
attacked, explain most of his illustrations by the simple forms. The fact
is, as was said before, that no one has analyzed or systematized the
phenomena, and so one cannot find clear, decisive statements to quote.

At any rate, whether previous authorities have agreed that such a process
is present or not, it is worth while to tackle the question; and the
formation of associations by imitation, if it occurs, is an important
division of the formation of associations in general. The experiments and
their results may now be described.

IMITATION IN CHICKS

No. 64 learned to get out of a certain pen (16 × 10 inches) by crawling
under the wire screening at a certain spot. There was also a chance to
get out by walking up an inclined plane and then jumping down. No. 66 was
put in with 64. After 9 minutes 20 seconds, 66 went out by the inclined
plane, although 64 had in the meantime crawled out under the screen 9
times. (As soon as he got out and ate a little he was put back.) It was
impossible to judge how many of these times 66 really saw 64 do this.
He was looking in that direction 5 of the times. So also, in three more
trials, 66 used the inclined plane, though 64 crawled under each time. 67
was then tried. In 4 minutes 10 seconds, he crawled under, 64 having done
so twice. Being then put in _alone_, he, without the chance to imitate,
still crawled under. So probably he went under _when with 64_ not by
imitation but by accident, just as 64 had learned the thing himself.

[Illustration: Fig. 19. Fig. 20.]

The accompanying figure (19) shows the apparatus used in the next
experiment. A represents the top of a box (5 × 4 inches), 13 inches above
the level of the floor C. On the floor C were the chicks and food. B is
the top of a box 10 inches high. Around the edges of A except the one
next B a wire screen was placed, and 65 was repeatedly put upon A until
he learned to go quickly back to C _via_ B. Then the screen was bent
outward at X so that a chick could barely squeeze through and down (A to
C). Eleven chicks were then one at a time placed on A with 65. In every
case but one they went A-C. In the case of the chick (75) who went A-B-C,
there could have been no imitation, for he went down _before_ 65 did. One
other went through the hole before 65 went to B. The remaining nine all
had a chance to imitate 65 and to save the uncomfortable struggle to get
through the hole, 65 going A-B-C 8 times before 68 went A-C, 2 times when
with 66 and 76, once in the case of each of the others.

In still another experiment the apparatus was (as shown in Fig. 20) a
pen 14 inches square, 10 inches high, with a wire screen in front and a
hole 3½ inches square in the back. This hole opened into a passageway (B)
leading around to C, where were the other chicks and food. Chicks who had
failed, when put in alone, to find the way out, were put in with other
chicks who had learned the way, to see if by seeing them go out they
would learn the way. Chick 70 was given 4 trials alone, being left in the
box 76 minutes all told. He was then given 9 trials (165 minutes) with
another chick who went out _via_ B 36 times. 70 failed to follow him on
any occasion. The trials were all given in the course of two days. Chick
73 failed in 1 trial (12 minutes) to get out of himself, and was then
given 4 trials (94 minutes) with another chick who went out _via_ B 33
times. In this experiment, as in all others reported, sure evidence that
the animals wanted to get out, was afforded by their persistent peckings
and jumpings at the screen or bars that stood between them and C. Chick
72, after 8 unsuccessful trials alone (41 minutes), was given 8 trials
with a chance to imitate. After the other chick had gone out 44 times,
72 _did go out_. He did not follow the other but went 20 seconds later.
It depends upon one’s general opinion whether one shall attribute this
one case out of three to accident or imitation.

I also took two chicks, one of whom learned to escape from A (in Fig. 19)
by going to B and jumping down the side to the _right_ of A, the other
of whom learned to jump down the side to the _left_, and placed them
together upon A. Each took his own course uninfluenced by the other in 10
trials.

Chicks were also tried in several pens where there was only one possible
way of escape to see if they would learn it _more quickly_ when another
chick did the thing several times before their eyes. The method was
to give some chicks their first trial with an imitation possibility
and their second without, while others were given their first trial
without and their second with. If the ratio of the average time of the
first trial to the average time of the second is smaller in the first
class than it is in the second class, we may find evidence of this
sort of influence by imitation. Though imitation may not be able to
make an animal _do_ what he would otherwise _not do_, it may make him
do _quicker_ a thing he would have done sooner or later any way. As a
fact the ratio is _much larger_. This is due to the fact that a chick,
when in a pen with another chick, is not afflicted by the discomfort
of loneliness, and so does not try so hard to get out. So the other
chick, who is continually being put in with him to teach him the way
out, really prolongs his stay in. This factor destroys the value of
these quantitative experiments, and I do not insist upon them as
evidence against imitation, though they certainly offer none for it. I
do not give descriptions of the apparatus used in these experiments or
a detailed enumeration of the results, because in this discussion we
are not dealing primarily with imitation as a slight general factor
in forming experience, but as a definite associational process in the
mind. The utter absence of imitation in this limited sense is apparently
demonstrated by the results of the following experiments.

V was a box 16 × 12 × 8½, with the front made of wire screening and at
the left end a little door held by a bolt but in such a way that a sharp
peck at the top of the door would force it open.

W was a box of similar size, with a door in the same place fixed so that
it was opened by raising a bolt. To this bolt was tied a string which
went up over the top of the edge of the box and back across the box, as
in D. By jumping up and coming down with the head over this thread, the
bolt would be pulled up. The thread was 8½ inches above the floor.

X was a box of similar size, with door, bolt and string likewise. But
here the string continued round a pulley at the back down to a platform
in the corner of the box. By stepping on the platform the door was opened.

Y was a box 12 × 8 × 8½, with a door in the middle of the front, which I
myself opened when a chick pecked at a tack which hung against the front
of the box 1½ inches above the top of the door.

These different acts, pecking at a door, jumping up and with the neck
pulling down a string, stepping on a platform, and pecking at a tack,
were the ones which various chicks were given a chance to imitate. The
chicks used were from 16 to 30 days old. The method of experiment was
to put a chick in, leave him 60 to 80 seconds, then put in another who
knew the act, and on his performing it, to let both escape. No cases were
counted unless the imitator apparently saw the other do the thing. After
about ten such chances to learn the act, the imitator was left in alone
for ten minutes. The following table gives the results. The imitators,
of course, had previously failed to form the association of themselves. F
denotes failure to perform the act:

TABLE 4

======+=====+=========+============+==============
| |NO. TIMES| TIME IN |
CHICK | ACT | SAW |WHICH FAILED| FINAL TIME
------+-----+---------+------------+--------------
84 | V | 38 | 45.00 F | 15.00 F
85 | V | 30 | 30.00 F | 10.00 F
86 | V | 44 | 55.00 F | 15.00 F
87 | V | 26 | 35.00 F | 15.00 F
80 | W | 54 | 60.00 F | 15.00 F
81 | W | 40 | 45.00 F | 15.00 F
87 | W | 27 | 30.00 F | 10.00 F
81 | X | 18 | 20.00 F | 10.00 F
82 | X | 21 | 20.00 F | 8.40 _Did_
83 | X | 33 | 35.00 F | 15.00 F
84 | X | 46 | 55.00 F | 15.00 F
84 | Y | 45 | 55.00 F | 15.00 F
83 | Y | 29 | 35.00 F | 15.00 F
======+=====+=========+============+==============

Thus out of all these cases only one did the act in spite of the ample
chance for imitation. I have no hesitation in declaring 82’s act in
stepping on the platform the result of mere accident, and am sure that
any one who had watched the experiments would agree.

IMITATION IN CATS

By reference to the previous descriptions of apparatus, it will be seen
that box D was arranged with two compartments, separated by a wire
screen. The larger of these had a front of wooden bars with a door which
fell open when a string stretched across the top was bitten or clawed
down. The smaller was closed by boards on three sides and by the wire
screen on the fourth. Through the screen a cat within could see the one
to be imitated pull the string, go out through the door thus opened and
eat the fish outside. When put in this compartment, the top being covered
by a large box, a cat soon gave up efforts to claw through the screen,
quieted down and watched more or less the proceedings going on in the
other compartment. Thus this apparatus could be used to test the power of
imitation. A cat who had no experience with the means of escape from the
large compartment was put in the closed one; another cat, who would do it
readily, was allowed to go through the performance of pulling the string,
going out, and eating the fish. Record was made of the number of times he
did so and of the number of times the imitator had his eyes clearly fixed
on him. These were called ‘times seen.’ Cases where the imitator was
looking in the general direction of the ‘imitatee’ and might very well
have seen him and probably did, were marked ‘doubtful.’ In the remaining
cases the cat did not see what was done by his instructor. After the
imitatee had done the thing a number of times, the other was put in the
big compartment alone, and the time it took him before pulling the string
was noted and his general behavior closely observed. If he failed in 5
or 10 or 15 minutes to do so, he was released and not fed. This entire
experiment was repeated a number of times. From the times taken by the
imitator to escape and from observation of the way that he did it, we can
decide whether imitation played any part. The history of several cases
are given in the following tables. In the first column are given the
lengths of time that the imitator was shut up in the box watching the
imitatee. In the second column is the number of times that the latter did
the trick. In the third and fourth are the times that the imitator surely
and possibly saw it done, while in the last is given the time that, when
tried alone, the imitator took to pull the string, or if he failed,
the time he was in the box trying to get out. Times are in minutes and
seconds, failures denoted by F:

TABLE 5 (a)

=======================+=====================================+===========
| NO. 7 IMITATING NO. 2 |
--------------+--------+------------+-----------+------------+-----------
| Time |No. of times| No. of |No. of times| Time of 7
|Watching| 2 did |times 7 saw| Doubtful |when alone
--------------+--------+------------+-----------+------------+-----------
| 10.00 | 11 | 3 | 5 |
After 48 Hours| 11.00 | 10 | 4 | 2 |
| 12.00 | 20 | 4 | 13 | 10.00 F
| | | | | 1.00[8]
After 24 Hours| 8.00 | 20 | 6 | 11 | 3.30
| | | | | 10.00 F
| 13.00 | 25 | 8 | 12 | 20.00 F
After 24 Hours| 9.00 | 20 | 4 | 11 | 10.00 F
After 24 Hours| 12.00 | 35 | 5 | 21 | 30.00 F
After 2 Hours | 10.00 | 25 | 3 | 8 | 25.00 F
After 24 Hours| 15.00 | 35 | 6 | 21 | 20.00 F
After 24 Hours| 6.00 | 20 | 0 | 7 | 10.00 F
Total times surely and possibly seen,— 43 111 |
=============================================================+===========

TABLE 5 (b)

=======================+=====================================+===========
| NO. 5 IMITATING NO. 2 |
--------------+--------+------------+-----------+------------+-----------
| Time |No. of times| No. of |No. of times| Time of 5
|Watching| 2 did |times 5 saw| Doubtful |when alone
--------------+--------+------------+-----------+------------+-----------
| 12.00 | 15 | 3 | 8 | 5.00 F
After 2 Hours| 10.00 | 8 | 4 | 4 |
After 24 Hours| 5.00 | 5 | 0 | 3 |
After 1 Hour | 14.00 | 10 | 5 | 3 | 10.00 F
After 1 Hour | 13.00 | 22 | 7 | 11 | 10.00 F
After 24 Hours| 7.00 | 15 | 3 | 8 | 5.00 F
After 48 Hours| 18.00 | 20 | 2 | 9 | 20.00 F
After 24 Hours| 14.00 | 20 | 2 | 10 | 30.00 F
After 24 Hours| 10.00 | 20 | 7 | 12 | 20.00 F
Total times surely and possibly seen,— 33 68 |
=============================================================+===========

TABLE 5 (c)

=======================+=====================================+===========
| NO. 6 IMITATING NO. 2 |
--------------+--------+------------+-----------+------------+-----------
| Time |No. of times| No. of |No. of times| Time of 6
|Watching| 2 did |times 6 saw| Doubtful |when alone
--------------+--------+------------+-----------+------------+-----------
| 12.00 | 30 | 0 | 19 | 1.10[9]
After 48 Hours| 11.00 | 30 | 0 | 11 | 9.30
After 72 Hours| 10.00 | 30 | 0 | 15 | 3.00
After 72 Hours| 6.00 | 20 | 3 | 7 | 1.50
After 24 Hours| 9.00 | 30 | 1 | 13 | 10.00 F
After 24 Hours| 10.00 | 30 | 6 | 9 | 10.00 F
After 24 Hours| 10.00 | 30 | 1 | 8 | 9.40
Total times surely and possibly seen,— 11 82 |
=============================================================+===========

TABLE 5 (d)

=======================+=====================================+===========
| NO. 3 IMITATING NO. 2 |
--------------+--------+------------+-----------+------------+-----------
| 8.00 | 30 | 2 | 19 | 3.30[10]
| | | | | 3.30
After 48 Hours| 10.00 | 30 | 2 | 14 | .20
| | | | | .20
After 72 Hours| 10.00 | 30 | 2 | 8 | .18
| | | | | .08
Total times surely and possibly seen,— 6 41 |
=============================================================+===========

Before entering upon a discussion of the facts shown by these tables,
we must describe the behavior of the imitators, when, after seeing 2
pull the string, they were put in alone. In the opinion of the present
observer there was not the slightest difference between their behavior
and that of cats 4, 10, 11, 12 and 13, who were put into the same
position without ever having seen 2 escape from it. 6, 7, 5 and 3 paid
no more attention to the string than they did, but struggled in just
the same way. No one, I am sure, who had seen them, would have claimed
that their conduct was at all influenced by what they had seen. When
they did hit the string the act looked just like the accidental success
of the ordinary association experiment. But, besides these personal
observations, we have in the impersonal time-records sufficient proofs
of the absence of imitation. If the animals pulled the string from
having seen 2 do so, they ought to pull it in each individual case at
an approximately regular length of time after they were put in, and
presumably pretty soon thereafter. That is, if an association between
the sight of that string in that total situation and a certain impulse
and consequent freedom and food had been formed in their minds by the
observation of the acts of 2, they ought to pull it _on seeing it_, and
if any disturbing factor required that a certain time should elapse
before the imitative faculty got in working order, that time ought to be
somewhere near constant. The times were, as a fact, long and irregular
in the extreme. Furthermore, if the successful cases were even in part
due to imitation, the times ought to decrease the more they saw 2 do the
thing. Except with 3, they _increase_ or give place to failures. Whereas
6 and 7, if they had been put in again immediately after their first
successful trial and from then on repeatedly, would have unquestionably
formed the association, they did not, when put in after a further
chance to increase their knowledge by imitation, do the thing as soon
as before. The case of 3 is not here comparable to the rest because he
_was_ given three trials in immediate succession. He was a more active
cat and quicker to learn, as may be seen by comparing his time curves
with those of 7, 6 and 5. That the mere speed with which he mastered
this association is no sign that imitation was present may be seen by
reference to the time curves of 4 and 13 (on p. 43).

Some cats were also experimented with in the following manner. They were
put into a box [No. 7 into box A (O at front), No. 5 into B (O at back)]
and left for from 45 to 75 seconds. Then a cat who knew the way to get
out was put in, and, of course, pulled at the loop and opened the door.
_Both cats then went out and both were fed._ After the cat had been
given a number of such chances to learn by imitation, he was put in and
left until he did the thing, or until 5 or 10 minutes elapsed. As in the
preceding experiments, no change in their behavior which might signify
imitation was observed. No. 7 acted exactly like 3, or 10, or 11, when
put in the box, apparently forming the association by accident in just
the same way. Good evidence that he did not imitate is the fact that,
whereas 1 (whom he saw) pulled the loop with his teeth, 7 pulled it with
his paw. 5 failed to form the association, though he saw 3 do it 8 times
and probably saw him 18 times more. He did get out twice by clawing the
_string_ in the _front_ of the box, not the _loop_ in the _back_, as 3
did. These successes took place early in the experiment. After that he
failed when left alone to get out at all.

Another experiment was made by a still different method. My cats were
kept in a large box about 4 ft. high, the front of which was covered with
poultry-yard netting. Its top was a board which could be removed. To save
opening the door and letting them all loose, I was in the habit of taking
them out by the top when I wanted to experiment with them. Of course the
one who happened to climb up (perhaps attracted by the smell of fish
on my fingers) was most likely to be taken out and experimented with
and fed. Thus they formed the habit of climbing up the front of the box
whenever I approached. Of three cats which I obtained at the same time,
one did not after 8 or 10 days acquire this habit. Even though I held out
a piece of fish through the netting, he would not climb after it. It was
reasonable to suppose that imitation might overcome this sluggishness,
if there were any imitation. I therefore put two cats with him and had
them climb up 80 times before his eyes and get fish. He never followed or
tried to follow them.

4 and 3 had been subjected to the following experiment. I would make a
certain sound and after 10 seconds would go up to the cage and hold the
fish out to them through the netting at the top. They would then, of
course, climb up and eat it. After a while, they began to climb up upon
hearing the signal (4) or before the 10 seconds were up. I then took 12
and 10, who were accustomed to going up when they saw me approach, but
who had no knowledge of the fact that the signal meant anything, and gave
them each a chance to imitate 3. That is, one of them would be left in
the box with 3, the signal would be given, and after from 5 to 10 seconds
3 would climb up. At 10 seconds I would come up with food, and then,
of course, 12 would climb up. This was repeated again and again. The
question was whether imitation would lead them to form the association
more quickly than they would have done alone. It did not. That when at
last they did climb up before 10 seconds was past, that is, before I
approached with food, it was not due to imitation, is shown by the fact
that on about half of such occasions they climbed up _before 3 did_. That
is, they reacted to the _signal_ by _association_, not to his _movements_
by _imitation_.

IMITATION IN DOGS

Here the method was not to see if imitation could arouse more quickly an
act which accident was fairly likely to bring forth sooner or later, but
to see if, where accident failed, imitation would succeed.

3 was found to be unable of himself to escape from box BB1, and was then
given a chance to learn from watching 1. The back of box BB1 was torn
off and wire netting substituted for it. Another box with open front was
placed directly behind and against box BB1. No. 3, who was put in this
second box, could thus see whatever took place in and in front of box BB1
(O at back, high). The record follows:—

TABLE 6 (a)

=======================================+================================
| DOG 3 IMITATING DOG 1
--------------------------------+------+------+--------------+----------
| Times| Times|Times probably| Time
| 1 did| 3 saw| 3 saw | in alone
--------------------------------+------+------+--------------+----------
| 30 | 7 | 14 | 3.00 F
After 1 Hour | 35 | 9 | 14 | 3.00 F
After 1 Hour | 10 | 3 | 3 | 5.00 F
After 24 Hours | 20 | 6 | 8 |
| 30 | 8 | 13 | 6.00 F
After 48 Hours | 25 | 8 | 11 | 8.00 F
| 25 | 6 | 12 | 6.00 F
| 25 | 9 | 7 | 10.00 F
After 24 Hours | 30 | 10 | 11 | 40.00 F
| | | |
Total times surely and possibly seen,— 66 93 |
=============================================================+==========

A similar failure to imitate was observed in the case of another simple
act. No. 1, as may be seen on page 60, had learned to escape from a pen
about 8 by 5 feet by jumping up and biting a cord which ran from one end
of the pen to the other and at the front end was tied to the bolt which
held the door. Dogs 2 and 3 had failed in their accidental jumping and
pawing to hit this cord, and were then given a chance to learn by seeing
1 do so, escape, and, of course, be fed. 1 always jumped in the same way,
biting the cord at the same place, namely, where a loose end from a knot
in it hung down 4 or 5 inches. 2 and 3 would either be tied up in the pen
or left in a pen at one side. They had a perfect chance to see 1 perform
his successful act. After every twenty or thirty performances by 1, 2 and
3 would be put in alone. It should be remembered that here, as also in
the previous experiment and all others, the imitators certainly _wanted_
to get out when thus left in alone. They struggled and jumped and pawed
and bit, but they never jumped _at the cord_. Their records follow:—

TABLE 6 (b)

=======================================+==============================
| DOG 2 IMITATING DOG 1
--------------------------------+------+------+---------+-------------
| Times| Times| Times | Time 2 was
| 1 did| 2 saw| Doubtful| in alone
--------------------------------+------+------+---------+-------------
| 30 | 9 | 11 | 10.00 F
After 1 Hour | 30 | 10 | 9 | 10.00 F
After 48 Hours | 25 | 8 | 8 |
After 1 Hour | 10 | 3 | 4 | 9.00 F[11]
After 24 Hours | 30 | 8 | 12 | 15.00 F
After 1 Hour | 30 | 9 | 12 | 15.00 F
After 48 Hours | 20 | 7 | 6 | 10.00 F
| 20 | 8 | 7 |
After 48 Hours | 30 | 6 | 8 | 15.00 F
After 24 Hours | 15 | 2 | 4 | 10.00 F
Total times surely and possibly seen,— 70 81 |
========================================================+=============

TABLE 6 (c)

=======================================+==============================
| DOG 3 IMITATING DOG 1
--------------------------------+------+------+---------+-------------
| Times| Times| Times | Time 3 was
| 1 did| 3 saw| Doubtful| in alone
--------------------------------+------+------+---------+-------------
| 30 | 10 | 10 | 10.00 F
After 1 Hour | 30 | 9 | 10 | 10.00 F
After 1 Hour | 15 | 6 | 4 |
After 24 Hours | 30 | 9 | 11 | 15.00 F
After 24 Hours | 30 | 10 | 12 | 15.00 F
After 1 Hour | 30 | 8 | 9 | 10.00 F
After 48 Hours | 20 | 6 | 7 | 40.00 F
After 1 Hour | 20 | 6 | 5 |
After 48 Hours | 30 | 8 | 9 | 15.00 F
After 24 Hours | 15 | 3 | 4 | 20.00 F
Total times surely and possibly seen,— 75 81 |
========================================================+=============

Another corroborative, though not very valuable, experiment was the
following: Dog 3 had been taught for the purpose of another experiment
to jump up on a box and beg when I held a piece of meat above the box. I
then caused him to do this 110 times (within two days) in the presence of
1. Although 1 saw him at least 20 per cent of the times (3 was always fed
each time he jumped on the box), he never tried to imitate him.

It seems sure from these experiments that the animals were unable
to form an association leading to an act from having seen the other
animal, or animals, perform the act in a certain situation. Thus we
have further restricted the association process. Not only do animals
not have associations accompanied, more or less permeated and altered,
by inference and judgment; they do not have associations of the sort
which may be acquired from other animals by imitation. What this implies
concerning the actual mental content accompanying their acts will be
seen later on. It also seems sure that we should give up imitation as an
_a priori_ explanation of any novel intelligent performance. To say that
a dog who opens a gate, for instance, need not have reasoned it out _if
he had seen another dog do the same thing_, is to offer, instead of one
false explanation, another equally false. Imitation in any form is too
doubtful a factor to be presupposed without evidence. And if a general
imitative faculty is not sufficiently developed to succeed with such
simple acts as those of the experiments quoted, it must be confessed that
the faculty is in these higher mammals still rudimentary and capable
of influencing to only the most simple and habitual acts, or else that
for some reason its sphere of influence is limited to a certain class
of acts, possessed of some _qualitative difference_ other than mere
simplicity, which renders them imitable. The latter view seems a hard
one to reconcile with a sound psychology of imitation or association at
present, without resorting to instinct. Unless a certain class of acts
are by the innate mental make-up especially tender to the influence of
imitation, the theory fails to find good psychological ground to stand
on. The former view may very well be true. But in any case the burden
of proof would now seem to rest upon the adherents to imitation; the
promising attitude would seem to be one which went without imitation
as long as it could, and that is, of course, until it surely found it
present.

Returning to imitation considered in its human aspect, to imitation
as a transferred association in particular, we find that here our
analytical study of the animal mind promises important contributions to
general comparative psychology. If it is true, and there has been no
disagreement about it, that the primates do imitate acts of such novelty
and complexity that only this out-and-out kind of imitation can explain
the fact, we have located one great advance in mental development. Till
the primates we get practically nothing but instincts and individual
acquirement through impulsive trial and error. Among the primates we
get also acquisition by imitation, one form of the increase of mental
equipment by tradition. The child may learn from the parent quickly
without the tiresome process of seeing for himself. The less active and
less curious may share the progress of their superiors. The brain whose
impulses hitherto could only be dislodged by specific sense-impressions
may now have any impulse set agoing by the sight of the movement to which
it corresponds.

All this on the common supposition that the primates _do_ imitate, that
a monkey in the place of these cats and dogs _would_ have pulled the
string. My apology for leaving the matter in this way without experiments
of my own is that the monkey which I procured for just this purpose
failed in two months to become tame enough to be thus experimented on.
Accurate information about the nature and extent of imitation among
the primates should be the first aim of further work in comparative
psychology, and will be sought by the present writer as soon as he can
get subjects fit for experiments.

In a questionnaire which was sent to fifteen animal trainers,
the following questions were asked:—

1. “If one dog was in the habit of ‘begging’ to get food and
another dog saw him do it ten or twenty times, would the second
dog then beg himself?”

2. “In general is it easier for you to teach a cat or dog a
trick if he has seen another do it?”

3. “In general do cats imitate each other? Do dogs? Do
monkeys?”

4. “Give reasons for your opinion, and please write all the
reasons you have.”

Five gentlemen (Messrs. R. C. Carlisle, C. L. Edwards, V. P. Wormwood, H.
S. Maguire and W. E. Burke) courteously responded to my questionnaire.
All are trainers of acknowledged reputation. To these questions on
imitation four replied.

To the first question we find the following answers: (_a_) “Most dogs
would.” (_b_) “Yes; he will very likely do it. He will try and imitate
the other dog _generally_.” (_c_) “If a young dog with the mother, it
would be very apt to.... With older dogs, it would depend very much upon
circumstances.” (_d_) “He would not.”

To 2 the answers were: (_a_) “Very much easier.” (_b_) “It is always
easier if they see another one do it often.” (_c_) “This would also
depend on certain conditions. In teaching to jump out of a box and
in again, seeing another might help, but in teaching something very
difficult, I do not think it would be the case.” (_d_) “It is not.”

To 3 the answers were: (_a_) “Yes. Some. More than either dogs or cats.”
(_b_) “Yes. Yes. Yes.” (_c_) “In certain things, yes; mostly in those
things which are in compliance to the laws of their own nature.” (_d_)
“No. No. Yes, they are born imitators.”

The only definite answer to question 4 was: “Take a dog or cat and close
them up in a room and go in and out several times, and you will find that
they will go to the door and stand up on their hind legs with front paws
on the door knob and try to open the door to get out. I could also give
you a hundred more such reasons.” This was given by (_b_).

The replies to a test question, however, go to show that these opinions
regarding imitation may be mistaken. Question 8 was: “If you wanted to
teach a cat to get out of a cage by opening an ordinary thumb latch and
then pushing the door, would you take the cat’s paw and push down the
thumb piece with it and then push the door open with the paw, or would
you just leave the cat inside until it learned the trick itself?” The
second is certainly the better way, as will be seen in a later part of
this paper, and pushing the latch with the cat’s paw has absolutely no
beneficial influence on the formation of the association, yet (_a_) and
(_b_) both chose the first way, and (_c_) answered ambiguously. Further,
the only reason given is, of course, no reason at all. It proves too
much, for if there were such imitation as that, my cats and dogs would
surely have done the far simpler things required of them. I cannot find
that trainers make any practical use of imitation in teaching animals
tricks, and on the whole I think these replies leave the matter just
where it was before. They are mere opinions—not records of observed
facts. It seems arrogant and may seem to some unjustifiable thus to
discard testimony, to stick to a theory based on one’s own experiments in
the face of these opinions. If I had wished to gain applause and avoid
adverse criticism, I would have abstained from upholding the radical
view of the preceding pages. At times it seems incredible to me that the
results of my experiments should embody the truth of the matter, that
there should be no imitation. The theory based on them seems, even to me,
too radical, too novel. It seems highly improbable that I should be right
and all the others wrong. But I cannot avoid the responsibility of giving
what seems to my judgment the most probable explanation of the results of
the experiments; and that is the radical explanation already given.

THE MENTAL FACT IN ASSOCIATION

It is now time to put the question as to just what is in an animal’s
mind when, having profited by numerous experiences, he has formed the
association and does the proper act when put in a certain box. The
commonly accepted view of the mental fact then present is that the sight
of the inside of the box reminds the animal of his _previous pleasant
experience after escape_ and _of the movements_ which he made which were
immediately followed by and so associated with that escape. It has been
taken for granted that _if the animal remembered the pleasant experience
and remembered the movement, he would make the movement_. It has been
assumed that the association was _an association of ideas_; that when
one of the ideas was of a movement the animal was capable of making
the movement. So, for example, Morgan says, in the ‘Introduction to
Comparative Psychology’: “If a chick takes a ladybird in its beak forty
times and each time finds it nasty, this is of no practical value to the
bird unless the sight of the insect suggests _the nasty taste_” (p. 90).

Again, on page 92, Morgan says, “_A race after the ball_ had been
suggested through the channel of olfactory sensations.” Also, on page
86 “... the visual impression suggested the idea or representation of
unpleasant gustatory experience.” The attitude is brought out more
completely in a longer passage on page 118: “On one of our first ascents
one of them put up a young coney, and they both gave chase. Subsequently
they always hurried on to this spot, and, though they never saw another
coney there, reiterated disappointment did not efface _the memory of
that first chase_, or so it seemed.” That is, according to Morgan, the
dogs thought of the chase and its pleasure, on nearing the spot where it
had occurred, and so hurried on. On page 148 of ‘Habit and Instinct,’ we
read, “Ducklings so thoroughly associated water with the sight of their
tin that they tried to drink from it and wash in it when it was empty,
nor did they desist for some minutes,” and this with other similar
phenomena is attributed to the ‘association by contiguity’ of human
psychology.

From these quotations it seems fairly sure that if we should ask Mr.
Morgan, who is our best comparative psychologist, what took place in the
mind of one of these cats of our experiments during the performance of
one of the ‘tricks’ he would reply: “The cat performs the act because
of the association of ideas. He is reminded by the sight of the box and
loop of his experience of pulling that loop and of eating fish outside.
So he goes and pulls it again.” This view has stood unchallenged, but its
implication is false. It implies that an animal, whenever it thinks of
an act, can supply an _impulse to do_ the act. It takes for granted that
the performance of a cat who gets out of a box is mentally like that of
a man who thinks of going down street or of writing a letter and then
does it. The mental process is not alike in the two cases, for animals
can _not_ provide the impulse to _do_ whatever act they think of. _No cat
can form an association leading to an act unless there is included in
the association an impulse of its own which leads to the act._ There is
no general storehouse from which the impulse may be supplied after the
association is formed.

Before describing the experiments which justify these statements, it will
be worth while to recall the somewhat obvious facts about the composition
of one of these associations. There might be in an association, such as
is formed after experience with one of our boxes, the following elements:—

1. Sense-impression of the interior of the box, etc.

2. (_a_) Discomfort and (_b_) desire to get out.

3. Representation of oneself pulling the loop.

4. Fiat comparable to the human “I’ll do it.”

5. The impulse which actually does it.

6. Sense-impression of oneself pulling the loop, seeing one’s paw in a
certain place, feeling one’s body in a certain way, etc.

7. Sense-impression of going outside.

8. Sense-impression of eating, and the included pleasure.

Also between 1 and 4 we may have 9, representations of one’s experience
in going out, 10, of the taste of the food, etc. 6, 7 and 8 come after
the act and do not influence it, of course, except in so far as they
are the basis of the future 3’s, 9’s and 10’s. About 2 we are not at
present disputing. Our question is as to whether 3 or 5 is the essential
thing. In human associations 3 certainly often is, and the animals
have been credited with the same kind. Whatever he _thinks_, Professor
Morgan surely _talks_ as if 1 aroused 9 and 10 and 3 and leaves 5 to be
supplied at will. We have affirmed that 5 is the essential thing, that no
association without a specific 5 belonging to it and acquired by it can
lead to an act. Let us look at the reasons.

A cat has been made to go into a box through the door, which is then
closed. She pulls a loop and comes out and gets fish. She is made to go
in by the door again, and again lets herself out. After this has happened
enough times, the cat will of her own accord go into the box after eating
the fish. It will be hard to keep her out. The old explanation of this
would be that the cat associated the memory of being in the box with the
subsequent pleasure, and therefore performed the equivalent of saying
to herself, “Go to! I will go in.” The thought of _being in_, they say,
makes her _go in_. _The thought of being in will not make her go in._
For if, instead of pushing the cat toward the doorway or holding it
there, and thus allowing it to itself give the impulse, to innervate the
muscles, to walk in, you shut the door first and drop the cat in through
a hole in the top of the box, she will, after escaping as many times
as in the previous case, _not_ go into the box of her own accord. She
has had exactly the same opportunity of connecting the idea of being in
the box with the subsequent pleasure. Either a cat cannot connect ideas,
representations, at all, or she has not the power of progressing from the
thought of being in to the act of going in. The only difference between
the first cat and the second cat is that the first cat, in the course of
the experience, has the impulse to crawl through that door, while the
second has not the impulse to crawl through the door or to drop through
that hole. So, though you put the second cat on the box beside the hole,
she doesn’t try to get into the box through it. The impulse is the _sine
qua non_ of the association. The second cat has everything else, but
cannot supply that. These phenomena were observed in six cats, three of
which were tried by the first method, three by the second. Of the first
three, one went in himself on the 26th time and frequently thereafter,
one on the 18th and the other on the 37th; the two last as well as the
first did that frequently in later trials. The other three all failed to
go in themselves after 50, 60 and 75 trials, respectively.

The case of No. 7 was especially instructive, though not among these six.
No. 7 had had some trials in which it was put in through the door, but
ordinarily in this particular experiment was dropped in. After about 80
trials it would frequently exhibit the following phenomena: It would,
after eating the fish, go up to the doorway and, rushing from it, search
for fish. The kitten was very small and would go up into the doorway,
whirl round and dash out, all in one quick movement. The best description
of its behavior is the paradoxical one that it went out without going
in. The association evidently concerned what it had _done_, what it had
an impulse for, namely, _coming out through that door_ to get fish, not
what it remembered, had a representation of.

Still more noteworthy evidence is found in the behavior of cats and
dogs who were put in these boxes, left one or two minutes, and then
put through the proper movement. For example, a cat would be put in B
(O at back) and left two minutes. I would then put my hand in through
the top of the box, take the cat’s paw and with it pull down the loop.
The cat would then go out and eat the fish. This would be done over and
over again, and after every ten or fifteen such trials the cat would be
left in alone. If in ten or twenty minutes he did not escape, he would
be taken out through the top and not fed. In one series of experiments
animals were taken and thus treated in boxes from which their own
impulsive activity had failed to liberate them. The results, given in
the table below, show that no animal who fails to perform an act in the
course of his own impulsive activity will learn it by being put through
it.

In these experiments some of the cats and all of the dogs but No. 1
showed no agitation or displeasure at my handling from the very start.
Nor was there any in Dog 1 or the other cats after a few trials. It may
also be remarked that in the trials alone which took place during and
at the end of the experiment the animals without exception showed that
they did not fail to perform the act from lack of a desire to get out.
They all tried hard enough to get out and would surely have used the
association if they had formed it.

TABLE 7

===========+===============================+==============+============+
Individual | Apparatus |Time in which |Number of |
| |impulsive |times the |
| |activity |animal was |
| |failed to lead|put through |
| |to the act |the movement|
-----------+-------------------------------+--------------+------------+
Cat 1 | F (String outside unfastened) | 55.00 | 77 |
Cat 5 | G (Thumb latch) | 57.00 | 59 |
Cat 7 | G (Thumb latch) | 50.00 | 30 |
Cat 2 | G (Thumb latch) | 54.00 | 141 |
Dog 2 | BB1 (O at back, high) | 48.00 | 30 |
Dog 3 | BB1 (O at back, high) | 20.00 | 85 |
Dog 2 | M (Lever outside) | 15.00 | 95 |
Dog 1 | FF[12] | 30.00 | 110 |
Chick 89 | X (see page 53) | 20.00 | 30 |
Cat 13 | KKK,[13][14] | 40.00 | 65 |
===========+===============================+==============+============+

===========+===============================+===============+========
Individual | Apparatus |Time in which |Time of
| |this experience|final
| |failed to lead |trial
| |to the act |
-----------+-------------------------------+---------------+--------
Cat 1 | F (String outside unfastened) | 120.00 | 20.00
Cat 5 | G (Thumb latch) | 55.00 | 10.00
Cat 7 | G (Thumb latch) | 35.00 | 10.00
Cat 2 | G (Thumb latch) | 110.00 | 20.00
Dog 2 | BB1 (O at back, high) | 80.00 | 60.00
Dog 3 | BB1 (O at back, high) | 55.00 | 10.00
Dog 2 | M (Lever outside) | 140.00 | 30.00
Dog 1 | FF[12] | 135.00 | 60.00
Chick 89 | X (see page 53) | 60.00 | 30.00
Cat 13 | KKK,[13][14] | 60.00 | 10.00
============+===============================+===============+========

Now, the only difference between the experiences of the animals in these
experiments and their experiences in those where they let themselves
out, is that here they only saw and felt themselves making the movement,
whereas in the other case they also felt the impulse, gave the
innervation. That, then, is the essential. It may be objected that the
animals failed because they did not _attend_ to the process of being put
through the movement, that, had they attended to it, they would later
themselves have made the movement. It is, however, improbable that out
of fifty times an animal should not have attended to what was going on
at least two or three times. But if seeing himself do it was on a par
with feeling an impulse to and so doing it, even two or three times
would suffice to start the habit. And it is even more improbable that an
experience should be followed by keen pleasure fifty times and not be
attended to with might and main, unless animals attend _only_ to their
own impulses and the excitements thereof. But if the latter be true, it
simply affirms our view from a more fundamental standpoint.

In another set of experiments animals were put in boxes with whose
mechanisms they had had no experience, and from which they might or
might not be able to escape by their own impulsive acts. The object was
to see whether the time taken to form the association could be altered
by my instruction. The results turned out to give a better proof of the
inability to form an association by being put through the act than any
failure to change the time-curve. For it happened in all but one of
the cases that the movement which the animal made to open the door was
different from the movement which I had put him through. Thus, several
cats were put through (in Box C [button]) the following movement: I took
the right paw and, putting it against the lower right-hand side of the
button, pushed it round to a horizontal position. The cats’ ways were
as follows: No. 1 turned it by clawing vigorously at its top; No. 6, by
pushing it round with his nose; No. 7, in the course of an indiscriminate
scramble at first, in later trials either by pushing with his nose or
clawing at the top, settling down finally to the last method. Nos. 2 and
5 did it as No. 1 did. Cat 2 was tried in B (O at back). I took his paw
and pressed the loop with it, but he formed the habit of clawing and
biting the string at the top of the box near the front. No. 1 was tried
in A. I pressed the loop with his paw, but he formed the habit of biting
at it.

In every case I kept on putting the animal through the act every time,
if at the end of two minutes (one in several cases) it had not done it,
even after it had shown, by using a different way, that my instruction
had no influence. I never succeeded in getting the animal to change its
way for mine. Moreover, if any one should fancy that the animal really
profited by my instruction so as to learn what result to attain, namely,
the turning of a certain button, but chose a way of his own to turn
it, he would be deluding himself. The time taken to learn the act with
instruction was no shorter than without.

If, then, an animal happens to learn an act by being put through it, it
is just happening, nothing more. Of course, you may _direct_ the animal’s
efforts so that he will perform the act himself the sooner. For instance,
you may hold him so that his accidental pawing will be sure to hit the
vital point of the contrivance. But the animal cannot form an association
leading to an act unless the particular impulse to that act is present as
an element of the association; he cannot supply it from a general stock.
The groundwork of animal associations is not the association of _ideas_,
but the association of idea or sense-impression with _impulse_.

In the questionnaire mentioned elsewhere, some questions were asked with
a view to obtaining corroboration or refutation of this theory that an
impulse or innervation is a necessary element in every association formed
if that association leads to an act. The questions and answers were:—

_Question 1_: “If you wanted to teach a horse to tap seven times with his
hoof when you asked him, ‘How many days are there in a week?,’ would you
teach him by taking his leg and making him go through the motions?”

_A_ answered, “Yes! at first.”

_B_ answered, “No! I would not.”

_C_ answered, “At first, yes!”

_D_ answered, “No!”

_Question 2_: “Do you think you _could_ teach him that way, even if
naturally you would take some other way?”

_A_ answered, “In time, yes!”

_B_ answered, “I think it would be a very hard way.”

_C_ answered, “Certainly I do.”

_D_ answered, “I do not think I could.”

_E_ answered, “Yes.”

_Question 3_: “How would you teach him?”

_A_ answered, “I should tap his foot with a whip, so that he would raise
it, and reward him each time.”

_B_ answered, “I should teach him by the motion of the whip.”

_C_ answered, “First teach him by pricking his leg the number of times
you wanted his foot lifted.”

_D_ answered, “You put figure 2 on blackboard and touch him on leg twice
with cane, and so on.”

_E_ answered ambiguously.

It is noteworthy that even those who think they _could_ teach an animal
by putting him through the trick do not use that method, except at first.
And what they really do then is probably to stimulate the animal to the
reflex act of raising his hoof. The hand simply replaces the cane or
whip as the means of stimulus. The answers are especially instructive,
because the numerous counting tricks done by trained horses seem, at
first, to be incomprehensible, unless the trainer can teach the horse by
putting it through the movement the proper number of times. The counting
tricks performed by Mascot, Professor Maguire’s horse, were quoted to me
by a friend as incomprehensible on my theory. The answers given above
show how simple the thing really is. All the counting-tricks of all the
intelligent horses depend on the fact that a horse raises his hoof when
a certain stimulus is given. One simple reaction gives the basis for a
multitude of tricks. In the same way other tricks, which at first sight
seem to require that the animal should learn by being put through the
movement, may depend on some simple reflex or natural impulse.

Another question was, “How would you teach a cat to get out of a box, the
door of which was closed with a thumb latch?”

_A_ answered, “I should use a puffball as a plaything for the cat to claw
at.” This means, I suppose, that he would get the cat to claw at the
puffball and thus direct its clawings to the vicinity of the thumb piece.

_B_ answered, “I would put the cat in and get it good and hungry and then
open the door by lifting the latch with my finger. Then put some food
that the cat likes outside, and she will soon try to imitate you and so
learn the trick.”

_C_ answered, “I would first adjust all things in connection with the
surroundings of the cat so they would be applicable to the laws of its
nature, and then proceed to teach the trick.”

I suppose this last means that he would fix the box so that some of the
cat’s instinctive acts would lead it to perform the trick. The answer
given by _B_ means apparently that he would simply leave the thing to
accident, for any such imitation as he supposes is out of the question.
At all events, none of these would naturally start to teach the trick by
putting the animal through the motions, which, were it a possible way,
would probably be a traditional one among trainers. On the whole, I see
in these data no reason for modifying our dogma that animals cannot learn
acts without the impulse.

Presumably the reader has already seen budding out of this dogma a new
possibility, a further simplification of our theories about animal
consciousness. The possibility is that animals may have _no images or
memories at all, no ideas to associate_. Perhaps the entire fact of
association in animals is the presence of sense-impressions with which
are associated, by resultant pleasure, certain impulses, and that,
therefore, and therefore only, a certain situation brings forth a certain
act. Returning to our analysis of the association, this theory would say
that there was no (9) or (10) or (3) or (4), that the sense-impression
gave rise, when accompanied by the feeling of discomfort, to the impulse
(5) directly, without the intervention of any representations of the
taste of the food, or the experience of being outside, or the sight of
oneself doing the act. This theory might be modified so as to allow
that the representations could be there, but to deny that they were
necessary, were inevitably present, that the impulse was connected to the
sense-impression through them. It would then claim that the effective
part of the association was a direct bond between the situation and the
impulse, but would not cut off the possibility of there being an aura
of memories along with the process. It then becomes a minor question of
interpretation which will doubtless sooner or later demand an answer. I
shall not try to answer it now. The more radical question, the question
of the utter exclusion of representative trains of thought, of any
genuine association of _ideas_ from the mental life of animals, is
worth serious consideration. I confess that, although certain authentic
anecdotes and certain experiments, to be described soon, lead me to
reject this exclusion, there are many qualities in animals’ behavior
which seem to back it up. If one takes his stand by a rigid application
of the law of parsimony, he will find justification for this view which
no experiments of mine can overthrow.

Of one thing I am sure, and that is that it is worth while to state the
question and how to solve it, for although the point of view involved is
far removed from that of our leading psychologists to-day, it cannot long
remain so. I am sorry that I cannot pretend to give a final decision.

The view seems preposterous because, if an animal has sense-impressions
when his brain is excited by currents starting in the end-organs,
it seems incredible that he should not be conscious in imagination
and memory by having similar excitations caused from within. We are
accustomed to think of memory as the companion of sensation. But,
after all, it is a question of fact whether the connections in the
cat brain include connections between present sensation-neuroses and
past sensation-neuroses. The only connections may be those between the
former and impulse-neuroses, and there is no authoritative reason why
we should suppose any others unless they are demonstrated by the cat’s
behavior. This is just the point at issue. Such evidence as the phenomena
of animals’ dreams does not at all prove the presence of memory or
imagination. A dog may very well growl in his sleep without any idea of
a hostile dog. The impulse to growl _may_ be caused by chance excitement
of its own neurosis without any sensation-neurosis being concerned.
_Acts_ of recognition may have no _feelings_ of recognition going with or
causing them. A sense-impression of me gets associated in my dog’s mind
with the impulses to jump on me, lick my hand, wag his tail, etc. If,
after a year, the connection between the two has lasted, he will surely
jump on me, lick my hand and wag his tail, though he has not and never
had any representation of me.

The only logical way to go at this question and settle it is, I think,
to find some associations the formation of which requires the presence
of images, of ideas. You have to give an animal a chance to associate
sense-impression A with sense-impression B and then to associate B
with some act C so that the presence of B in the mind will lead to the
performance of C. Presumably the representation of B, if present,
will lead to C just as the sense-impression B did. Now, if the chance
to associate B with A has been improved, you ought, when the animal is
confronted with the sense-impression A, to get a revival of B and so
the act C. Such a result would, if all chance to associate C with A had
been eliminated, demonstrate the presence of representations and their
associations. I performed such an experiment in a form modified so as to
make it practicable with my animals and resources. Unfortunately, this
modification spoils the crucial nature of the experiment and robs it of
much of its authority. The experiment was as follows:—

A cat was in the big box where they were kept (see p. 90) very hungry.
As I had been for a long time the source of all food, the cats had grown
to watch me very carefully. I sat, during the experiment, about eight
feet from the box, and would at intervals of two minutes clap my hands
four times and say, “I must feed those cats.” Of course the cat would at
first feel no impulse except perhaps to watch me more closely when this
signal was given. After ten seconds had elapsed I would take a piece of
fish, go up to the cage and hold it through the wire netting, three feet
from the floor. The cat would then, of course, feel the impulse to climb
up the front of the cage. In fact, experience had previously established
the habit of climbing up whenever I moved toward the cage, so that in the
experiment the cat did not ordinarily wait until I arrived there with the
fish. In this experiment

A = The sense-impression of my movements and voice when giving the signal.

B = The sense-impression of my movements in taking fish, rising, walking
to box, etc.

C = The act of climbing up, with the impulse leading thereunto.

The question was whether after a while A would remind the cat of B, and
cause him to do C before he got the _sense-impression_ of B, that is,
before the ten seconds were up. If A leads to C through a memory of B,
animals surely _can_ have association of ideas proper, and probably often
_do_. Now, as a fact, after from thirty to sixty trials, the cat does
perform C immediately on being confronted by A or some seconds later,
at all events before B is presented. And it is my present opinion that
their action is to be explained by the presence, through association, of
the idea B. But it is not impossible that A was associated _directly_
with the impulse to C, although that impulse was removed from it by
ten seconds of time. Such an association is, it seems to me, highly
improbable, unless the neurosis of A, and with it the psychosis,
continues until the impulse to C appears. But if it does so continue
during the ten seconds, and thus get directly linked to C, we have
exactly a representation, an image, a memory, in the mind for eight of
those ten seconds. It does not help the deniers of images to substitute
an image of A for an image of B. Yet, unless they do this, they have
to suppose that A comes and goes, and that after ten seconds C comes,
and, passing over the intervening blank, willfully chooses out A and
associates itself with it. There are some other considerations regarding
the behavior of the cats from the time the signal was given till they
climbed up, which may be omitted in the hope that it will soon be
possible to perform a decisive experiment. If an observer can make sure
of the animal’s attention to a sequence A-B, where B does not arouse any
impulse to an act, and then later get the animal to associate B with C,
leaving A out this time, he may then, if A, when presented anew, arouses
C, bid the deniers of representations to forever hold their peace.

Another reason for allowing animals representations and images is found
in the longer time taken to form the association between the act of
licking or scratching and the consequent escape. If the associations in
general were simply between situation and impulse and act, one would
suppose that the situation would be associated with the impulse to lick
or scratch as readily as with the impulse to turn a button or claw a
string. Such is not the case. By comparing the curves for Z on pages
57-58 with the others, one sees that for so simple an act it takes a
long time to form the association. This is not a final reason, for lack
of attention, a slight increase in the time taken to open the door after
the act was done, or an absence of preparation in the nervous system for
connections between these particular acts and definite sense-impressions,
may very well have been the cause of the difficulty in forming the
associations. Nor is it certain that _ideas_ of clawing loops would be
easier to form than ideas of scratching or licking oneself. The matter
is still open to question. But, as said before, my opinion would be that
animals _do_ have representations and that such are the beginning of the
rich life of ideas in man. For the most part, however, such are confined
to specific and narrow practical lines. There was no evidence that my
animals habitually _did_ form associations of ideas from their experience
throughout, or that such were constantly revived without the spur of
immediate practical advantage.[15]

Before leaving the topic an account may be given of experiments similar
to the one described above as performed on Cats 3 and 4, which were
undertaken with Cat 13 and Dogs 1, 2 and 3.

Cat 13 was fed with pieces of fish at the top of the wire netting 45
times, to accustom it to climbing up when it saw me come with fish. I
then went through the same process as with 3 and 4, but at intervals of
60 to 90 seconds instead of 120. After 90 such trials it occasionally
climbed up a little way, but though 135 trials in all were given, it
never made the uniform and definite reaction which 3 and 4 did. It
reacted, when it reacted at all, at from 5 to 9 seconds after the
signal. Whether age, weight, lack of previous habitual climbing when I
approached, or a slowness in forming the association made the difference,
is uncertain.

Dog 1 was experimented on in the following manner: I would put him in a
big pen, 20×10 feet, and sit outside facing it, he watching me as was
his habit. I would pound with a stick and say, “Go over to the corner.”
After an interval (10 seconds for 35 trials, 5 seconds for 60 trials)
I would go over to the corner (12 feet off) and drop a piece of meat
there. He, of course, followed and secured it. On the 6th, 7th, 16th,
17th, 18th and 19th trials he did perform the act before the 10 seconds
were up, then for several times went during the two-minute intervals
without regarding the signal, and finally abandoned the habit altogether,
although he showed by his behavior when the signal was given that he was
not indifferent to it.

Dogs 1, 2 and 3 were also given 95, 135 and 95 trials, respectively,
the acts done being (1) standing up against the wire netting inclosing
the pen, (2) placing the paws on top of a keg, and (3) jumping up onto
a box. The time intervals were 5 seconds in each case. No dog of these
ever performed the act before I started to take the meat to feed them,
but they did show, by getting up if they were lying down when the signal
was given, or by coming to me if they were in some other part of the
pen, that something was suggested to them by it. Why these cases differ
from the cases of Cats 3 and 4 (10 and 12 also presented phenomena like
those reported in the cases of 3 and 4) is an interesting though not
very important question. The dogs were not kept so hungry as were the
cats, and experience had certainly not rendered the particular impulses
involved so sensitive, so ready to discharge. Dogs 2 and 3 were older.
There is no reason to invoke any qualitative difference in the mental
make-up of the animals until more illuminating experiments are made.

ASSOCIATION BY SIMILARITY AND THE FORMATION OF CONCEPTS

What there is to say on this subject from the standpoint of my
experiments will be best introduced by an account of the experiments
themselves.

Dog 1 had escaped from AA (O at front) 26 times. He was then put in
BB (O at back). Now, whereas 2 and 3, who were put in without previous
experience with AA, failed to paw the loop in BB, No. 1 succeeded. His
times were 7.00, .35, 2.05, .40, .32, .10, 1.10, .38, .10, .05, and from
then on he pawed the loop as soon as put in the box. After a day or so he
was put in BB1 (O at back high). Although the loop was in a new position,
his times were only .20, .10, .10, etc. After nine days he was put in a
box arranged with a little wooden platform 2½ inches square, hung where
the loop was in BB1. Although the platform resembled the loop not the
least save in position, his times were only .10, .07, .05, etc.

[Illustration: FIG. 21.]

From the curves given in Figure 21, which tell the history of 10, 11 and
12 in B1 (O at back) after each had previously been familiarized with A
(O at front), we see this same influence of practice in reacting to one
mechanism upon the time taken to react to a mechanism at all similar. It
naturally takes a cat a longer time to accidentally claw a loop in the
back than in the front, yet a comparison of these curves with those on
page 39, Figure 2, shows the opposite to have been the case with 10, 11
and 12. The same remarkable quickness was noted in Cats 1 and 3 when put
into B (O at back) after learning A (O at front). Moreover, the loops
were not alike. The loop in A was of smaller wire, covered with a bluish
thread, while the loop in B was covered with a black rubber compound, the
diameter of the loop being three times that of A’s loop.

If any advocate of reason in animals has read so far, I doubt not that
his heart has leaped with joy at these two preceding paragraphs. “How,”
he will say, “can you explain these facts without that prime factor in
human reason, association by similarity? Surely they show the animal
perceiving likenesses and acting from general ideas.” _This is the very
last thing that they show._ Let us see why they do not show this and what
they do show. He who thinks that these animals had a general notion of a
loop-like thing as the thing to be clawed, that they felt the loop in B,
different as it was in size, color and position, to be still a loop, to
have the essential quality of the other, must needs presuppose that the
cat has a clear, accurate sensation and representation of both. Only if
the cat discriminates can it later associate by noticing similarities.
This is what such thinkers do presuppose. A bird, for instance, dives
in the same manner into a river of yellow water, a pond or an ocean.
It has a general notion, they say, of water. It knows that river water
is one thing and pond water another thing, but it knows that both are
water, _ergo_, fit to dive into. The cat who reacts to a loop of small
wire of a blue color knows just what that loop is, and when it sees a
different loop, knows its differences, but knows also its likeness, and
reacts to the essential. Thus crediting the cat with our differentiation
and perception of individuality, they credit it with our conceptions and
perceptions of similarity. Unless the animal has the first, there is no
reason to suppose the last. Now, _the animal does not have either_.
It does not in the first place react to that particular loop in A,
with recognition of its qualities. It reacts to a vague, ill-defined
sense-impression, undiscriminated and even unperceived in the technical
sense of the word. Morgan’s phrase, “a bit of pure experience,” is
perhaps as good as any. The loop is to the cat what the ocean is to a
man, when thrown into it when half-asleep. Thus the cat who climbed up
the front of the cage whenever I said, “I must feed those cats,” would
climb up just as inevitably when I said, “My name is Thorndike,” or
“To-day is Tuesday.” So cats would claw at the loop or button when the
door was open. So cats would paw at the place where a loop had been,
though none was there. The reaction is not to a well-discriminated
object, but to a vague situation, and any element of the situation may
arouse the reaction. The whole situation in the case of man is speedily
resolved into elements; the particular elements are held in focus, and
the non-essential is systematically kept out of mind. In the animal the
whole situation sets loose the impulse; all of its elements, including
the non-essentials, get yoked with the impulse, and the situation may
be added to or subtracted from without destroying the association,
provided you leave something which will set off the impulse. The animal
does not think one is like the other, nor does it, as is so often said,
mistake one for the other. It does not think _about_ it at all; it just
thinks _it_, and the _it_ is the kind of “pure experience” we have
been describing. In human mental life we have accurate, discriminated
sensations and perceptions, realized as such, and general notions, also
realized as such. Now, what the phenomena in animals which we have been
considering show is that they have neither. Far from showing an advanced
stage of mentality, they show a very primitive and unspecialized stage.
They are to be explained not by the presence of _general_ notions, but by
the absence of notions of _particulars_. The idea that animals react to
a particular and absolutely defined and realized sense-impression, and
that a similar reaction to a sense-impression which varies from the first
proves an association by similarity, is a myth. We shall see later how an
animal does come in certain cases to discriminate, in one sense of the
word, with a great degree of delicacy, but we shall also see then what
must be emphasized now, that naturally the animal’s brain reacts very
coarsely to sense-impressions, and that the animal does not think about
his thoughts at all.

This puts a new face upon the question of the origin and development of
human abstractions and consequent general ideas. It has been commonly
supposed that animals had ‘recepts’ or such semi-abstractions as Morgan’s
‘predominants,’ and that by associating with these, arbitrary and
permanent signs, such as articulate sounds, one turned them into genuine
ideas of qualities. Professor James has made the simple but brilliant
criticism that all a recept really means is _a tendency to react in a
certain way_. But I have tried to show that the fact that an animal
reacts alike to a lot of things gives no reason to believe that it is
conscious of their common quality and reacts to that consciousness,
because the things it reacts to in the first place are not the
hard-and-fast, well-defined ‘things’ of human life. What a ‘recept’ or
‘predominant’ really stands for is no thing which can be transformed into
a notion of a quality by being labelled with a name. This easy solution
of the problem of abstraction is impossible. A true idea of the problem
itself is better than such a solution.

My statement of what has been the course of development along this line
is derived from observations of animals’ behavior and Professor James’
theory of the nature of and presumable brain processes going with the
abstractions and conceptions of human consciousness, but it is justified
chiefly by its harmony with the view that conception, the faculty of
having general notions, has been naturally selected by reason of its
utility. The first thing is for an animal to learn to react alike only
to things which resemble each other in the _essential_ qualities. On an
artificial, analytic basis, feelings of abstract qualities might grow out
of reacting alike to objects similar in such a respect that the reaction
would be useless or harmful. But in the actual struggle for existence,
starting with the mammalian mind as we have found it, you will tend to
get reactions to the _beneficial_ similarities by selection from among
these so-called mistakes, _before you get any general faculty of noticing
similarities_. In order that this faculty of indifferent reaction to
different things shall grow into the useful faculty of indifferent
reaction to different things _which have all some quality that makes the
reaction a fit one_, there must be a tremendous range of associations.
For a lot of the similarities which are non-essential have to be stamped
out, not by a power of feeling likeness, but by their failure to lead to
pleasure. With such a wide range of associations we may get reactions
on the one hand where impulses have been connected with one particular
sense-impression because when connected with all others they had failed
to give pleasure, and on the other hand, reactions where an impulse has
been connected with numerous different impressions possessing one common
quality, and disconnected with all impressions, otherwise like these,
which fail to have that one quality.

Combined with this multiplication of associations, there is, I think, an
equally important factor, the loosening of the elements of an association
from one another and from it as a whole. Probably the idea of the look
of the loop or lever or thumb latch never entered the mind of any one of
my cats during the months that they were with me, except when the front
end of the association containing it was excited by putting the cat
into the box. In general, the unit of their consciousness, apart from
impulses and emotions, is a whole association-series. Such soil cannot
grow general ideas, for the ideas, so long as they never show themselves
except for a particular practical business, will not be thought about
or realized in their nature or connections. If enough associations are
provided by a general curiosity, such as is seen among the monkeys,
if the mental elements of the association are freed, isolated, felt
by themselves, _then_ a realization of the ideas, feelings of their
similarity by transition from one to the other, feelings of qualities
and of meanings, may gradually emerge. Language will be a factor in the
isolation of the ideas and a help to their realization. But when any
one says that language has been the cause of the change from brute to
man, when one talks as if _nothing but it_ were needed to turn animal
consciousness into human, he is speaking as foolishly as one who should
say that a proboscis added to a cow would make it an elephant.

This is all I have to say, in this connection, about association by
similarity and conception, and with it is concluded our analysis of the
nature of the association-process in animals. Before proceeding to treat
of the delicacy, complexity, number and permanence of these associations,
it seems worth while to attempt to describe graphically, not by analysis,
the mental fact we have been studying, and also to connect our results
with the previous theories of association.

One who has seen the phenomena so far described, who has watched the
life of a cat or dog for a month or more under test conditions, gets,
or fancies he gets, a fairly definite idea of what the intellectual
life of a cat or dog feels like. It is most like what we feel when
consciousness contains little thought about anything, when we feel the
sense-impressions in their first intention, so to speak, when we feel our
own body, and the impulses we give to it. Sometimes one gets this animal
consciousness while in swimming, for example. One feels the water, the
sky, the birds above, but with no thoughts _about_ them or memories of
how they looked at other times, or æsthetic judgments about their beauty;
one feels no _ideas_ about what movements he will make, but feels himself
make them, feels his body throughout. Self-consciousness dies away.
Social consciousness dies away. The meanings, and values, and connections
of things die away. One feels sense-impressions, has impulses, feels the
movements he makes; that is all.

This pictorial description may be supplemented by an account of some
associations in human life which are learned in the same way as are
animal associations; associations, therefore, where the process of
formation is possibly homologous with that in animals. When a man
learns to swim, to play tennis or billiards, or to juggle, the process
is something like what happens when the cat learns to pull the string
to get out of the box, provided, of course, we remove, in the man’s
case, all the accompanying mentality which is not directly concerned in
learning the feat.[16] Like the latter, the former contains desire,
sense-impression, impulse, act and possible representations. Like it, the
former is learned gradually. Moreover, the associations concerned cannot
be formed by imitation. One does not know how to dive just by seeing
another man dive. You cannot form them from being put through them,
though, of course, this helps indirectly, in a way that it does not with
animals. One makes use of no feelings of a common element, no perceptions
of similarity. The tennis player does not feel, “This ball coming at
this angle and with this speed is similar in angle, though not in speed,
to that other ball of an hour ago, therefore I will hit it in a similar
way.” He simply feels an impulse from the sense-impression. Finally,
the elements of the associations are not isolated. No tennis player’s
stream of thought is filled with free-floating representations of any of
the tens of thousands of sense-impressions or movements he has seen and
made on the tennis court. Yet there is consciousness enough at the time,
keen consciousness of the sense-impressions, impulses, feelings of one’s
bodily acts. So with the animals. There is consciousness enough, but of
this kind.

Thus, the associations in human life, which compare with the simple
connections learned by animals, are associations involving connections
between novel, complex and often inconstant sense-impressions and
impulses to acts similarly novel, complex and often inconstant. Man has
the elements of most of his associations in isolated form, attended
to separately, possessed as a permanent fund, recallable at will, and
multifariously connected among themselves, but with these associations
which we have mentioned, and with others like them, he deals as the
animals deal with theirs. The process, in the man’s mind, leaving out
extraneous mental stuff, may be homologous to the association-process
in animals. Of course, by assiduous attention to the elements of these
associations, a man may isolate them, may thus get these associations
to the same plane as the rest. But they pass through the stage we have
described, even then, and with most men, stay there. The abstraction, the
naming, etc., generally come from observers of the game or action, and
concern things as felt by them, not by the participant.

CRITICISM OF PREVIOUS THEORIES

We may now look for a moment at what previous writers have said about the
nature of association in animals. The complaint was made early in this
book that all the statements had been exceedingly vague and of no value,
except as retorts to the ‘reason’ school. In the course of the discussion
I have tried to extricate from this vagueness definite statements about
imitation, association of ideas, association by ideas. There is one more
theory, more or less hidden in the vagueness,—the theory that association
in animals is the same as association in man, that the animal mind
differs from the human mind only by the absence of reason and what it
implies. Presumably, silence about what association is, means that it is
the association which human psychology discusses. When the silence is
broken, we get such utterances of this theory as the following:—

“I think we may say then that the higher animals are able to proceed a
long way in the formation and definition of highly complex constructs,
analogous to but probably differing somewhat from those which we form
ourselves. These constructs, moreover, through association with
reconstructs, or representations, link themselves in trains so that a
sensation, or group of sensations, may suggest a series of reconstructs,
or a series of remembered phenomena.” (C. L. Morgan, Animal Life and
Intelligence, p. 341.)

“Lastly, before taking leave of the subject of the chapter, I am
most anxious that it should not be thought that, in contending that
intelligence is not reason, I wish in any way to disparage intelligence.
Nine tenths at least of the actions of average men are intelligent and
not rational. Do we not all of us know hundreds of practical men who are
in the highest degree intelligent, but in whom the rational, analytic
faculty is but little developed? Is it any injustice to the brutes to
contend that their inferences are of the same order as those of these
excellent practical folk? In any case, no such injustice is intended;
and if I deny them self-consciousness and reason, I grant to the higher
animals perceptions of marvelous acuteness and intelligent inferences of
wonderful accuracy and precision—intelligent inferences in some cases,
no doubt, more perfect even than those of man, who is often disturbed by
many thoughts” (_ibid._, pp. 376-377).

“Language and the analytic faculty it renders possible differentiate man
from the brute” (_ibid._, p. 376).

Here, as elsewhere, it should be remembered that Lloyd Morgan is not
quoted because he is the worst offender or because he represents the
opposite in general of what the present writer takes to be the truth. On
the contrary, Morgan is quoted because he is the least offender, because
he has taken the most advanced stand along the line of the present
investigation, because my differences from him are in the line of his
differences from other writers. With the theory of the passages just
quoted, however, which attribute extensive association of ideas and
general powers comparable to those of men minus reason, to the brutes,
and which repeat the time-honored distinction by language, I do not, in
the least, agree. Association in animals does not equal association in
man. The latter is built over and permeated and transformed by inference
and judgment and comparison; it includes imitation in our narrow sense
of transferred association; it obtains where no impulse is included; it
thus takes frequently the form of long trains of thought ending in no
pleasure-giving act; its elements are often loose, existing independently
of the particular association; the association is not only thought,
but at the same time thought _about_. None of these statements may
be truthfully made of animal association. Only a small part of human
association is at all comparable to it. My opinion of what that small
part is has already been given. Moreover, further differences will be
found as we consider the data relating to the delicacy, complexity,
number, and permanence of associations in animals. I said a while ago
that man was no more an animal with language than an elephant was a cow
with a proboscis. We may safely broaden the statement and say that _man
is not an animal plus reason_. It has been one great purpose of this
investigation to show that even after leaving reason out of account,
there are tremendous differences between man and the higher animals.
The problem of comparative psychology is not only to get human reason
from some lower faculties, but to get human _association_ from animal
association.

Our analysis, necessarily imperfect because the first attempted, of the
nature of the association-process in animals is finished, and we have now
to speak of its limitations in respect to delicacy, complexity, number
and permanence.

DELICACY OF ASSOCIATIONS

It goes without saying that the possible delicacy of associations is
conditioned by the delicacy of sense-powers. If an animal doesn’t feel
differently at seeing two objects, it cannot associate one with one
reaction, the other with another. An equally obvious factor is attention;
what is not attended to will not be associated. Beyond this there is no
_a priori_ reason why an animal should not react differently to things
varying only by the most delicate difference, and I am inclined to think
an animal could; that any two objects with a difference appreciable
by sensation which are also able to win attention may be reacted to
differently. Experiments to show this are very tedious, and the practical
question is, “What will the animal naturally attend to?” The difficulty,
as all trainers say, is to get the animal’s attention to your signal
somehow. Then he will in time surely react differently, if you give him
the chance, to a figure 7 on the blackboard from the way he does to a
figure 8, to your question, “How many days are there in a week?” and to
your question, “How many legs have you?” The chimpanzee in London that
handed out 3, 4, 5, 6, or 7 straws at command was not thereby proved of
remarkable intelligence or of remarkably delicate associative power. Any
reputable animal trainer would be ashamed to exhibit a horse who could
not do as much ‘counting’ as that. The maximum of delicacy in associating
exhibited by any animal, to my knowledge, is displayed in the performance
of the dog ‘Dodgerfield,’ exhibited by a Mr. Davis, who brings from four
cards, numbered 1, 2, 3 and 4, whichever one his master shall _think of_.
That is, you write out an arbitrary list, e.g. 4, 2, 1, 3, 3, 2, 2, 1,
4, 2, etc., and hand it to Mr. Davis, who looks at the list, thinks of
the first number, says “Attention! Dodger!” and then, “Bring it.” This
the dog does and so on through the list. Mr. Davis makes no signals which
anyone sitting even right beside or in front of him can detect. Thus the
dog exceeds the human observers in delicacy and associates each with
a separate act four attitudes of his master, which to human observers
seem all alike. Mr. Davis says he thinks the dog is a mind reader. I
think it quite possible that whatever signs the dog goes by are given
unconsciously and consist only of some very delicate general differences
in facial expression or the manner of saying the words, “Bring it,” or
slight sounds made by Mr. Davis in thinking to himself the words one or
two or three or four. Mr. Davis keeps his eyes shut and his hands behind
a newspaper. The dog looks directly at his face.

To such a height possible delicacy may attain, but possible delicacy is
quite another thing from actual untrained and unstimulated delicacy.
The difference in reaction has to be brought about by associating with
pleasure the reaction to the different sense-impression when it itself
differs and associating with pain tendencies to confuse the reactions.
The animal does not naturally as a function of sense-powers discriminate
at all delicately. Thus the cat who climbed up the wire netting when
I said, “I must feed those cats!” did not have a delicate association
of just that act with just those words. For after I had dropped the
clapping part of the signal and simply used those words, it would react
just as vigorously to the words, “To-morrow is Tuesday” or “My name is
Thorndike.” The reaction naturally was to a very vague stimulus. Taking
cat 10 when just beginning to learn to climb up at the signal, “I must
feed those cats!” I started in to improve the delicacy, by opposing to
this formula the formula, “I will not feed them,” after saying which, I
kept my word. That is, I gave sometimes the former signal and fed the
cats, sometimes the latter and did not. The object was to see how long
the cat would be in learning always to go up when I gave the first, never
to do so when I gave the second signal. I said the words in both cases
as I naturally would do, so that there was a difference in emphasis and
tone as well as in the mere nature of the syllables. The two signals were
given in all sorts of combinations so that there was no regularity in the
recurrence of either which might aid the animal. The cat at first did not
always climb up at the first signal and often _did_ climb up at the wrong
one. The change from this condition to one of perfect discrimination is
shown in the accompanying curves (Fig. 22), one showing the decrease in
_failures_ to respond to the wrong signal. The first curve is formed by
a line joining the tops of perpendiculars erected at intervals of 1 mm.
along the abscissa. The height of a perpendicular represents the number
of times the cat failed to respond to the food-signal in 20 trials, a
height of 1 mm. being the representative of one failure. Thus, the entire
curve stands for 280 trials, there being no failures after 60 trials, and
only 1 after the 40th.

[Illustration: FIG. 22.]

In the other curve, also, each 1 mm. along the abscissa stands for 20
trials, and the perpendiculars whose tops the curve unites represent the
number of times the cat in each 20 _did_ climb up at the signal which
meant no food. It will be seen that 380 experiences were necessary before
the animal learned that the second signal was different from the first.
The experiment shows beautifully the animal method of acquisition. If
at any stage the animal could have isolated the two ideas of the two
sense-impressions, and felt them together in comparison, this long and
tedious process would have been unnecessary.

It might be stated here that the animals also acquired associations of
moderate delicacy in discriminating between the different boxes. No cat
tried to get out of A or B by licking herself, for instance.

The question may naturally be raised that if naturally associations
are thus vague, the common phenomenon of a dog obeying his master’s
commands, and no one else’s, is inexplicable. The difference between
one man and another, one voice and another, it may be said, is not
much of a difference, yet is here uniformly discriminated, although we
cannot suppose any such systematic training to reject the other slightly
differing commands. My cats did not so discriminate. If any one else sat
in my chair and called out, “I must feed the cats,” they reacted, and
probably very many animals would, if untroubled by emotions of curiosity
or fear at the new individual, go through their tricks as well at
another’s voice as at that of their master. The other cases exemplify the
influence of attention. Repeated attention to these sense-impressions has
rendered them clear-cut and detailed, and the new impression consequently
does not equal them in calling forth the reaction.

The main thing to carry away from this discussion is the assurance that
the delicacy of the animal in associating acts with impressions is
nothing like the delicacy of the man who feels that a certain tone is
higher, or weight is heavier, than another, but _is_ like the delicacy
of the man who runs to a certain spot to hit one tennis ball and to a
different spot to hit one coming with a slightly different speed.

COMPLEXITY OF ASSOCIATIONS

An important question, especially if one wishes to rate an animal on a
scale of intelligence, is the question of how complex an association it
can form. A man can learn that to open a door he has to put the key in
its hole, turn it, turn the knob, and pull the door. Here, then, is a
complex act connected with the simple sense-impression. Or, conversely,
a man knows that when the ringing of a bell is followed by a whistle and
that by a red light he is to do a certain thing, while if any of the
three happens alone, he is not to. How far, then, we ask, can animals go
along the line of increased complexity in the associations?

We must not mistake for a complex association a series of associations,
where one sense-impression leads to an act such as to present a new
sense-impression which leads to another act which in its turn leads to
a new sense-impression. Of the formation of such _series_ animals are
capable to a very high degree. Chicks from 10 to 25 days old learned to
go directly through a sort of big labyrinth requiring a series of 23
distinct and in some cases fairly difficult associations, of which 11
involved choices between two paths. By this power of acquiring a long
series animals find their way to distant feeding grounds and back again.
But all such cases are examples of the _number_, not of the complexity,
of animal associations.

Some of my boxes were such as did give a chance for a complex association
to be formed. Such were G (thumb latch), J (double), K and L (triples)
for the cats, and O (triple) for the dogs. It would be possible for a
cat, after stepping on the platform in K, to notice that the platform was
in a different position, and so feel then a different sense-impression
from before, and thus turn the thing into a serial association. The
cat would then be like a man who on seeing a door should feel only the
impulse to stick the key in the hole, but then, seeing the door plus
a key in the hole, should feel the impulse to turn the key and so on
through. My cats did not give any signs of this, so that with them it
was either a complex association or an irregular happening of the proper
impulses. Probably the same was the case with Dog 1. Cats 10, 11, 12 in L
knew all the movements separately before being experimented on with the
combination. Cats 2, 3, 4 had had some experience of D, which worked by a
string something like the string part of K. The string in K was, however,
quite differently situated and required an altogether different movement
to pull it. Since further No. 2, who had had ten times as much experience
in D as 3 or 4, succeeded no better with the string element of K than
they, it is probable that the experience did not help very much. All else
in all these compound associations was new. At the same time the history
of these animals’ dealings with these boxes would not fairly represent
that of animals without general experience of clawing at all sorts of
loose or shaky things in the inside of a box. These cats had learned
to claw at all sorts of things. The time-curves were taken as in the
formation of the other associations, and, in addition, the order in which
the animal did the several things required was recorded in every trial.

In the case of all the curves, except the latter part of 3 in G, one
notices a very gradual slope and an excessive irregularity in the curve
throughout. Within the limits of the trials given the animals are unable
to form a perfect association and what advancement they make is very
slow. The case of 3 in G is not an exception to this, but a proof of it.
For 3 succeeded in making a perfect association, by accidentally hitting
on a way to turn the compound association into a simple one. He happened
one time to paw down the thumb piece at the same time that his other fore
limb, with which he was holding on between the door and the top of the
box, was pressing against the door. This giving him success he repeated
it in later trials and in a short time had it fixed as an element in a
perfect association. The marked change in his curve, from an irregular
and gradual slope at such a height as displayed a very imperfect
association, to a constant and very slight height, shows precisely the
change from a compound to a simple association.

Compound associations are formed slowly and not at all well. Further
observation shows that they were really not formed at all. For the
animals did not, except 3 in K for a certain period, do the several
things in a constant order, nor did they do them only once apiece. On the
contrary, an animal would pull the string several times after the bolt
had gone up with its customary click, and would do sometimes one thing
first, sometimes another. It may also be noted here, in advance of its
proper place, that these compound associations are far below the simple
in point of permanence. The conduct of the animals is clearly not that
of minds having associated with a certain box’s interior the idea of a
succession of three movements. The animal does not feel, “I did this and
that and that and got out,” or, more simply still, “this and that and
that means getting out.” If it did, we should soon see it doing what was
necessary without repetition and in a fairly constant time.

I imagine, however, that an animal could learn to associate with one
sense-impression a compound act so as to perform its elements in a
regular order. By arranging the box so that the second and third elements
of the act could be performed _only after the first had been_, and the
third _only after the first and second_, I am inclined to think you
could get a very vigorous cat to learn the elements in order and form
the association perfectly. The case is comparable to that of delicacy.
The cat does not _tend_ to know what he is doing or to depart from the
hit-or-miss method of learning, but by associating the other combinations
of elements with failure to get pleasure, as in delicacy experiments we
associated the reactions to all but the one signal, you could probably
stamp out all but the 1, 2, 3 order.

The fact that you have to thus maneuver to get the animals to have the
three impulses in a regular order shows that even when they are so,
there is no idea of the three as in an order, no thinking about them.
Representations do not get beyond their first intention. They are not
carried up into a free life which works them over anew. A complex _act_
does not imply a complex _thought_, or, more exactly, a performance of a
series does not imply the thought of a series. Consequently, since the
complexity of the act depends on the power which failure has to stamp out
all other combinations, it is far more limited than in man.

NUMBER OF ASSOCIATIONS

The patent and important fact is that there are so few in animals
compared to the human stock. Even after taking into account the various
acts associated with various smells, and exaggerating the possibility
of getting an equipment of associations in this field which man lacks,
one must recognize how far below man any animal is in respect to mere
quantity of associations. The associations with words alone of an
average American child of ten years far outnumber those of any dog. A
good billiard player probably has more associations in connection with
this single pastime than a dog with his whole life’s business. In the
associations which are homologous with those of animals man outdoes them
and adds an infinity of associations of a different sort. The primates
would seem, by virtue of their incessant curiosity and addition to
experience not for any practical purpose but merely for love of mental
life, to represent an advanced stage toward this tremendous quantity
of associations. In man not only this activity and curiosity, but also
education, increases the number of associations. Associations are
formed more quickly, and the absence of need for self-support during
a long infancy gives time. Associations thus formed work back upon
practical life, and by showing better ways decrease the need of work,
and so again increase the chance to form associations. The result in
the case of a human mind to-day is the possession of a thesaurus of
valuable associations, if the time has been wisely spent. The free life
of ideas, imitation, all the methods of communication, and the original
accomplishments which we may include under the head of invention, make
the process of acquisition in many cases quite a different one from the
trial and error method of the animals, and in general much shorten it.

Small as it is, however, the number of associations which an animal may
acquire is probably much larger than popularly supposed.

My cats and dogs did not mix up their acts with the wrong
sense-impressions. The chicks that learned the series of twenty-three
associations did not find it a task beyond their powers to retain
them. Several three-day-old chicks, which I caused to learn ten simple
associations in the same day, kept the things apart and on the next
morning went through each act at the proper stimulus. In the hands
of animal trainers some animals get a large number of associations
perfectly in hand. The horse Mascot is claimed to know the meaning of
fifteen hundred signals! He certainly knows a great many, and such as
are naturally difficult of acquisition. It would be an enlightening
investigation if some one could find out just how many associations a
cat or dog could form, if he were carefully and constantly given an
opportunity. The result would probably show that the number was limited
only by the amount of motive available and the time taken to acquire
each. For there is probably nothing in their brain structure which
limits the number of connections that can be formed, or would cause such
connections, as they grew numerous, to become confused.

In their anxiety to credit animals with human powers, the psychologists
have disregarded or belittled, perhaps, the possibilities of the strictly
animal sort of association. They would think it more wonderful that a
horse should respond differently to a lot of different numbers on the
blackboard than that he should infer a consequence from premises. But
if it be made a direct question of pleasure or pain to an animal, he
can associate any number of acts with different stimuli. Only he does
not form any associations until he has to, until the direct benefit is
apparent, and, for his ordinary life, comparatively few are needed.

On the whole our judgment from a comparison of man’s associations with
the brutes’ must be that a man’s are naturally far more delicate,
complex and numerous, and that in as far as the animals attain delicacy,
complexity, or a great number of associations, they do it by methods
which man uses only in a very limited part of the field.

PERMANENCE OF ASSOCIATIONS

Once formed, the connections by which, when an animal feels a certain
sense-impression, he does a certain thing, persist over considerable
intervals of time. With the curves on pages 39 to 58 and 60 to 65 are
given in many instances[17] additional curves showing the animal’s
proficiency after an interval without experience. To these data may be
added the following:—

The three chicks that had learned to escape through the long labyrinth
(involving twenty-three associations) succeeded in repeating the
performance after ten days’ interval. Similarly the chicks used as
imitators in V, W, X and Y did not fail to perform the proper act
after an interval of twenty days. Cat 6, who had had about a hundred
experiences in C (button), had the association as perfect after twenty
days as when it left off. Cat 2, who had had 36 experiences with C and
had attained a constant time of 8 seconds, escaped fourteen days later
in 3, 9 and 8 seconds, respectively, in three trials. Cat 1, after an
interval of twenty days, failed in 10 minutes to escape from C. The
signal for climbing up the front of the cage was reacted to by No.
3 after an interval of twenty-four days. No. 10, who had learned to
discriminate between ‘I must feed those cats’ and ‘I will not feed them,’
was tried after _eighty_ days. It was given 50 trials with the second
signal mingled indiscriminately with 25 trials with the first. I give
the full record of these, ‘yes’ equalling a trial in which she ‘forgot’
and climbed up, ‘no’ equalling a trial in which she wisely stayed down.
Dashes represent intervening trials with the first signal, _to which
she always reacted_. It will be observed that 50 trials put the cat in
the same position that 350 had done in her first experience, although in
that first experience she had had only about a hundred trials after the
association had been perfected. The association between the first signal
and climbing up was perfect after the eighty days.

TABLE 8

=======+========+========+========+========+========
TRIALS | TRIALS | TRIALS | TRIALS | TRIALS | TRIALS
1-7 | 8-17 | 18-27 | 28-35 | 36-42 | 43-50
-------+--------+--------+--------+--------+--------
— | yes | no | — | — | —
— | yes | yes | — | no | —
yes | yes | no | — | no | —
yes | — | no | no | — | —
no | yes | — | no | no | —
— | yes | — | yes | no | no
yes | no | yes | no | no | no
yes | yes | yes | — | — | yes
no | no | yes | no | — | no
no | — | yes | yes | no | no
— | — | no | no | no | no
— | yes | no | no | | no
— | yes | | | | no
| — | | | |
=======+========+========+========+========+========

All these data show that traces of the connections once formed are very
slow in being lost. If we allow that part of the time in the first trial
in all these cases is due to the time taken to realize the situation
(time not needed in the trials when the association is forming and the
animal is constantly being dropped into boxes), we may say that the
association is as firm as ever for a considerable time after practice
at it is stopped. How long a time would be required to annul the
influence of any given quantity of experience, say of an association
which had been gone through with ten times, I cannot say. It could, if
profitable, easily be determined in any case. The only case of total
loss of the association (No. 1 in C) is so exceptional that I fancy
something other than lapse of time was its cause. The main interest of
these data, considered as quantitative estimates, is not psychological,
but biological. They show what a tremendous advantage the well-developed
association-process is to an animal. The ways to different feeding
grounds, the actions of enemies, the appearance of noxious foods, are
all connected permanently with the proper reaction by a few experiences
which need be reënforced only very rarely. Of course, associations
without any permanence would be useless, but the usefulness increases
immensely with such a degree of permanence as these results witness. An
interesting experiment from the biological point of view would be to see
how infrequently an experience could occur and yet lead eventually to a
perfect association. An experiment approximating this is recorded in the
time-curves for Box H in Figure 7, on page 47. Three trials at a time
were given, the trials being two or three days apart. As may be seen from
the curves, the association was readily formed.

The chief psychological interest of these data is that they show that
permanence of associations _is not memory_. The fact that a cat, when
after an interval she is put into box G, proceeds to immediately press
the thumb piece and push the door, does not at all mean that the cat
feels the box to be the same from which she weeks ago freed herself by
pushing down that thumb piece, or thinks about ever having felt or done
anything in that box. She does not refer the present situation to a
situation of the past and realize that it is the same, but simply feels
on being confronted with that situation the same impulse which she felt
before. She does the thing now for just the same reason that she did it
before, namely, because pleasure has connected that act above all others
with that sense-impression, so that it is the one she feels like doing.
Her condition is that of the swimmer who starts his summer season after
a winter’s deprivation. When he jumps off the pier and hits the water,
he swims, not because he remembers that this is the way he dealt with
water last summer and so applies his remembrance to present use, but just
because experience has taught him to feel like swimming when he hits the
water. All talk about recognition and memory in animals, if it asserts
the presence of anything more than this, is a gross mistake. For real
memory is an absolute thing, including everything but forgetfulness. If
the cat had real memory, it would, when after an interval dropped into
a box, remember that from this box it escaped by doing this or that and
consequently, either immediately or after a time of recollection, go
do it, or else it would not remember and would fail utterly to do it.
On the contrary, we have all grades of _partial_ ‘forgetfulness,’ just
like the grades of swimming one might find if he dropped a dozen college
professors into the mill ponds of their boyhood, just like the grades of
forgetfulness of the associations once acquired on the ball field which
are manifested when on the Fourth of July the ‘solid men’ of a town get
out to amuse their fellow citizens. The animal makes attacks on a spot
around the vital one, or claws at the thing—but not so precisely as
before, or goes at it a while and then resorts to instinctive methods of
getting out. Its actions are exactly what would be expected of an animal
in whom the sense-impression aroused the impulse imperfectly, or weakly,
or intermittently, but are not at all like the actions of one who felt,
“I used to get out of this box by pulling that loop down.” In fact, the
record of No. 10 given on page 139 seems to be final on this point. If
at any time in the course of the 50 trials it had _remembered_ that ‘I
will not feed them’ meant ‘no fish,’ it would thenceforth have failed
to react. It would have stopped short in the ‘yes’ reactions, instead
of gradually decreasing their percentage. ‘Memory’ in animals, if one
still chooses to use the word, is _permanence of associations_, not the
presence of an idea of an experience attributed to the past.

To this proposition two corollaries may be added. First, these phenomena
of incomplete forgetfulness extend the evidence that animals do not have
a stock of independent ideas, the return of which, plus past associates,
equals memory. Second, there is, properly speaking, no continuity in
their mental streams. The present thought does not clutch the past to
its bosom or hold the future in its womb. The animal’s self is not a
being ‘looking before and after,’ but a direct practical association of
feelings and impulses. So far as experiences come continuously, they may
be said to form a continuous mental life, but there is no continuity
imposed from within. The feelings of its own body are always present, and
impressions from outside may come as they come to us. When the habit of
attending to the elements of its associations and raising them up into
the life of free ideas is acquired, these permanent bodily associations
may become the basis of a feeling of self-hood and the trains of ideas
may be felt as a continuous life.

INHIBITION OF INSTINCTS BY HABIT

One very important result of association remains to be considered, its
inhibition of instincts and previous associations. An animal who has
become habituated to getting out of a box by pulling a loop and opening
the door will do so even though the hole in the top of the box be
uncovered, whereas, if, in early trials, you had left any such hole, he
would have taken the instinctive way and crawled through it. Instances of
this sort of thing are well-nigh ubiquitous. It is a tremendous factor
in animal life, and the strongest instincts may thus be annulled. The
phenomenon has been already recognized in the literature of the subject,
a convenient account being found in James’ ‘Psychology,’ Vol. II, pages
394-397. In addition to such accounts, one may note that the influence
of association is exerted in two ways. The instinct may wane by not
being used, because the animal forms the habit of meeting the situation
in a different way, or it may be actually inhibited. An instance of the
former sort is found in the history of a cat which learns to pull a loop
and so escape from a box whose top is covered by a board nailed over it.
If, after enough trials, you remove a piece of the board covering the
box, the cat, when put in, will still pull the loop instead of crawling
out through the opening thus made. But, at any time, if she happens to
notice the hole, she _may_ make use of it. An instance of the second
sort is that of a chick which has been put on a box with a wire screen
at its edge, preventing her from jumping directly down, as she would
instinctively do, and forcing her to jump to another box on one side
of it and thence down. In the experiments which I made, the chick was
prevented by a second screen from jumping directly from the second box
also. That is, if in the accompanying figure, A is a box 34 inches high,
B a box 25 inches high, C a box 16 inches high, and D the pen with the
food and other chicks, the subject had to go A-B-C-D. The chick tried at
first to get through the screen, pecked at it and ran up and down along
it, looking at the chicks below and seeking for a hole to get through.
Finally it jumped to B and, after a similar process, to C. After enough
trials it forms the habit and when put on A goes immediately to B, then
to C and down. Now if, after 75 or 80 trials, you take away the screens,
giving the chick a free chance to go to D from either A or B, and then
put it on A, the following phenomenon appears. The chick goes up to the
edge, looks over, walks up and down it for a while, still looking down
at the chicks below, and then goes and jumps to B as habit has taught it
to do. The same actions take place on B. No matter how clearly the chick
sees the chance to jump to D, it does not do so. The impulse has been
truly inhibited. It is not the mere habit of going the other way, but the
impossibility of going _that_ way. In one case I observed a chick in whom
the instinct was all but, yet not quite, inhibited. When tried without
the screen, it went up to the edge to look over _nine times_, and at
last, after seven minutes, did jump straight down.

[Illustration: FIG. 23.]

ATTENTION

I have presupposed throughout one function which it will be well to now
recognize explicitly, attention. As usual, attention emphasizes and
facilitates the process which it accompanies. Unless the sense-impression
is focussed by attention, it will not be associated with the act which
comes later. Unless two differing boxes are attended to, there will be
no difference in the reactions to them. The really effective part of
animal consciousness, then, as of human, is the part which is attended
to; attention is the ruler of animal as well as human mind.

But in giving attention its deserts we need not forget that it is not
here comparable to the whole of human attention. Our attention to the
other player and the ball in a game of tennis _is_ like the animal’s
attention, but our attention to a passage in Hegel, or the memory which
flits through our mind, or the song we hear, or the player we idly watch,
is _not_. There ought, I think, to be a separate name for attention
when working for immediate practical associations. It is a different
species from that which holds objects so that we may define them, think
about them, remember them, etc., and the difference is, as our previous
sentence shows, not that between voluntary and involuntary attention. The
cat watching me for signs of my walking to the cage with fish is not in
the condition of the man watching a ball game, but in that of the player
watching the ball speeding toward him. There is a notable difference in
the permanence of the impression. The man watching the game can remember
just how that fly was hit and how the fielder ran for it, though he
bestowed only a slight quantity of attention on the matter, while the
fielder may attend to the utmost to the ball and yet not remember at all
how it came or how he ran for it. The one sort of attention leads you to
_think_ about a thing, the other to _act_ with reference to it. We must
be careful to remember that when we say that the cat attended to what was
said, we do not mean that he thereby established an idea of it. Animals
are not proved to form separate ideas of sense-impressions because they
attend to them, for the kind of attention they give is the kind which,
when given by men, results in practical associations, not in establishing
ideas of objects. If attention rendered clear the idea, we should not
have the phenomena of incomplete forgetfulness lately mentioned. The
animal would get a definite idea of just the exact thing done and would
do it or nothing. The human development of attention is in closest
connection with the acquisition of a stock of free ideas.

SOCIAL CONSCIOUSNESS

Besides attention there is another topic somewhat apart from our general
one, which yet deserves a few words. It concerns animals’ social
consciousness, their consciousness of the feelings of their fellows.
Do animals, for example, when they see others feeding, feel that the
others are feeling pleasure? Do they, when they fight, feel that the
other feels pain? So level-headed a thinker as Lloyd Morgan has said that
they do, but the conduct of my animals would seem to show that they did
not. For it has given us good reason to suppose that they do not possess
_any_ stock of isolated ideas, much less any abstracted, inferred, or
transferred ideas. These ideas of others’ feelings imply a power to
transfer states felt in oneself to another and realize them as there. Now
it seems that any ability to thus transfer and realize an idea ought to
carry with it an ability to form a transferred association, to imitate.
If the animal realizes the mental states of the other animal who before
his eyes pulls the string, goes out through the door, and eats fish,
he ought to form the association, ‘impulse to pull string, pleasure of
eating fish.’ This we saw the animal could not do.

In fact, pleasure in another, pain in another, is not a
sense-presentation or a representation or feeling of an object of any
sort, but rather a ‘meaning,’ a feeling ‘_of the fact that_.’ It can
exist only as something thought _about_. It is never ‘a bit of direct
experience,’ but an abstraction from our own life referred to that of
another.

I fancy that these feelings of others’ feelings may be connected pretty
closely with imitation, and for that reason may begin to appear in the
monkeys. There we have some fair evidence for their presence in the
tricks which monkeys play on each other. Such feelings seem the natural
explanation of the apparently useless tail-pullings and such like which
make up the attractions of the monkey cage. These may, however, be
instinctive forms of play-activity or merely examples of the general
tendency of the monkeys to fool with everything.

INTERACTION

I hope it will not be thought impertinent if from the standpoint of this
research I add a word about a general psychological problem, the problem
of interaction. I have spoken all along of the connection between the
situation and a certain impulse and act being stamped in when pleasure
results from the act and stamped out when it doesn’t. In this fact,
which is undeniable, lies a problem which Lloyd Morgan has frequently
emphasized. _How are pleasurable results able to burn in and render
predominant the association which led to them?_ This is perhaps the
greatest problem of both human and animal psychology. Unfortunately in
human psychology it has been all tangled up with the problems of free
will, mental activity, voluntary attention, the creation of novel acts,
and almost everything else. In our experiments we get the data which give
rise to the problem, in a very elementary form.

It should first be noted about the _fact_ that the pleasure does not
burn in an impulse and act themselves, but an impulse and act _as
connected with that particular situation_. No cat ever goes around
clawing, clawing, clawing all the time, because clawing in these boxes
has resulted in pleasure. Secondly, the connection thus stamped in
is _not contemporaneous, but prior to_ the pleasure. So much for the
fact; now for the explanation. I do not wish to rehearse or add to the
arguments with which so many pages have been already filled by scientists
and philosophers both. What we need most is not argument, but accurate
accounts of the mental fact and of the brain-process. But I do wish to
say to the parallelist, what has not to my knowledge been said, that if
he presupposes, to account for this fact, a ‘physical analogue of the
hedonic consciousness,’ it is his bounden duty to first show how any
motion in any neurone or group of neurones in the nervous system can
possess this power of stamping in any current which causes it. For no one
would, from our present knowledge of the brain, judge _a priori_ that any
motion in any part of it could be conceived which should be thus regnant
over all the others. And next he must show the possibility of the current
which represents the association being the excitant of the regnant motion
in a manner direct enough for the purpose.

I wish also to say that whoever thinks that, going along with the current
which parallels the association, there is an accompanying minor current,
which parallels the pleasure and which stamps in the first current when
present with it, flies directly in the face of the facts. _There is no
pleasure along with the association. The pleasure does not come until
after the association is done and gone._ It is caused by no such minor
current, but by the excitation of peripheral sense-organs when freedom
from confinement is realized or food is secured. Of course, the notion of
such a secondary subcurrent is mythology, anyway.

To the interactionist I would say: “Do not any more repeat in tiresome
fashion that consciousness _does_ alter movement, but get to work and
show when, where, in what forms and to what degrees it does so. Then,
even if it turns out to have been a physical parallel that did the work,
you will, at least, have the credit of attaining the best knowledge about
the results and their conditions, even though you misnamed the factor.”

Besides this contribution to general psychology, I think we may safely
offer one to pedagogical science. At least some of our results possess
considerable pedagogical interest. The fundamental form of intellection,
the association-process in animals, is one, we decided, which requires
the personal experience of the animal in all its elements. The
association cannot be taught by putting the animal through it or giving
it a chance to imitate. Now every observant teacher realizes how often
the cleverest explanation and the best models for imitation fail. Yet
often, in such cases, a pupil, if somehow enticed to do the thing, even
without comprehension of what it means, even without any real knowledge
of what he is doing, will finally get hold of it. So, also, in very
many kinds of knowledge, the pupil who does anything from imitation, or
who does anything from being put through it, fails to get a real and
permanent mastery of the thing. I am sure that with a certain type of
mind the only way to teach fractions in algebra, for example, is to get
the pupil to do, do, do. I am inclined to think that in many individuals
certain things cannot be learned save by actual performance. And I think
it is often a fair question, when explanation, imitation and actual
performance are all possible methods, which is the best. We are here
alongside the foundations of mental life, and this hitherto unsuspected
law of animal mind may prevail in human mind to an extent hitherto
unknown. The best way with children may often be, in the pompous words of
an animal trainer, ‘to arrange everything in connection with the trick
so that the animal will be compelled by the laws of his own nature to
perform it.’

This does not at all imply that I think, as a present school of
scientists seem to, that because a certain thing _has been_ in phylogeny
we ought to repeat it in ontogeny. Heaven knows that Dame Nature
herself in ontogeny abbreviates and skips and distorts the order of the
appearance of organs and functions, and for the best of reasons. We ought
to make an effort, as she does, to omit the useless and antiquated and
get to the best and most useful as soon as possible; we ought to change
what _is_ to what _ought to be_, as far as we can. And I would not
advocate this animal-like method of learning in place of the later ones
unless it does the same work better. I simply suggest that in many cases
where at present its use is never dreamed of, it may be a good method.
As the fundamental form of intellection, every student of _theoretical_
pedagogy ought to take it into account.

There is one more contribution, this time to anthropology. If the method
of trial and error, with accidental success, be the method of acquiring
associations among the animals, the slow progress of primitive man,
the long time between stone age and iron age, for instance, becomes
suggestive. Primitive man probably acquired knowledge by just this
process, aided possibly by imitation. At any rate, progress was not
by seeing through things, but by accidentally hitting upon them. Very
possibly an investigation of the history of primitive man and of the
present life of savages in the light of the results of this research
might bring out old facts in a new and profitable way.

Comparative psychology has, in the light of this research, two tasks
of prime importance. One is to study the passage of the child mind from
a life of immediately practical associations to the life of free ideas;
the other is to find out how far the anthropoid primates advance toward
a similar passage, and to ascertain accurately what faint beginnings
or preparations for such an advance the early mammalian stock may be
supposed to have had. In this latter connection I think it will be
of the utmost importance to bear in mind the possibility that _the
present anthropoid primates may be mentally degenerate_. Their present
aimless activity and incessant, but largely useless, curiosity may be
the degenerated vestiges of such a well-directed activity and useful
curiosity as led _homo sapiens_ to important practical discoveries,
such as the use of tools, the art of making fire, etc. It is even a
remote possibility that their chattering is a _relic_ of something like
language, not a _beginning_ of such. Comparative psychology should use
the phenomena of the monkey mind of to-day to find out what the primitive
mind from which man’s sprung off was like. That is the important thing
to get at, and the question whether the present monkey mind has not gone
back instead of ahead is an all-important question. A natural and perhaps
sufficient cause of degeneracy would be arboreal habits. The animal that
found a means of survival in his muscles might well lose the means before
furnished by his brain.

To these disconnected remarks still another must be added, addressed
this time to the anecdote school. Some member of it who has chanced to
read this may feel like saying: “This experimental work is all very
well. Your cats and dogs represent, it is true, specimens from the top
stratum of animal intelligence, and your negations, based on their
conduct, may be authoritative so far as concerns the average, typical
mammalian mind. But our anecdotes do not claim to be stories of the
conduct of the average or type, but of those exceptional individuals
who have begun to attain higher powers. And, if even a few dogs and
cats have these higher powers, our contention is, in a modified form,
upheld.” To all this I agree, provided the anecdote school now realize
just what sort of a position they hold. They are clearly in pretty much
the same position as spiritualists. Their anecdotes are on pretty much
the same level as the anecdotes of thought-transference, materializations
of spirits, supernormal knowledge, etc. Not in quite the same position,
for far greater care has been given by the Psychical Research Society to
establishing the criteria of authenticity, to insuring good observation,
to explaining by normal psychology all that can be so explained, in the
case of the latter than the anecdote school has done in the case of
the former. The off-hand explanation of certain anecdotes by invoking
reason, or imitation, or recognition, or feelings of qualities, is on a
par with the explanation of trance-phenomena and such like by invoking
the spirits of dead people. I do not deny that we may get lawfully a
supernormal psychology, or that the supernormal acts it finds may turn
out to be explained by these functions which I have denied to the normal
animal mind. But I must soberly declare that I think there is less
likelihood that such functions are the explanation of animal acts than
that the existence of the spirits of dead people is the true explanation
of the automatisms of spiritualistic phenomena. So much for the anecdote
school, if it calls itself by its right name and pretends only to give an
_abnormal_ animal psychology. The sad fact has been that it has always
pushed forward these exceptions as the essential phenomena of animal
mind. It has built up a general psychology from abnormal data. It is like
an anatomy written from observations on dime-museum freaks.

CONCLUSION

I do not think it is advisable here, at the close of this paper, to give
a summary of its results. The paper itself is really only such a summary
with the most important evidence, for the extent of territory covered
and the need of brevity have prevented completeness in explanation or
illustration. If the reader cares here, at the end, to have the broadest
possible statement of our conclusions and will take the pains to supply
the right meaning, we might say that our work has described a method,
crude but promising, and has made the beginning of an exact estimate of
just what associations, simple and compound, an animal can form, how
quickly he forms them, and how long he retains them. It has described
the method of formation, and, on the condition that our subjects were
representative, has rejected reason, comparison or inference, perception
of similarity, and imitation. It has denied the existence in animal
consciousness of any important stock of free ideas or impulses, and so
has denied that animal association is homologous with the association of
human psychology. It has homologized it with a certain limited form of
human association. It has proposed, as necessary steps in the evolution
of human faculty, a vast increase in the number of associations, signs of
which appear in the primates, and a freeing of the elements thereof into
independent existence. It has given us an increased insight into various
mental processes. It has convinced the writer, if not the reader, that
the old speculations about what an animal could do, what it thought, and
how what it thought grew into what human beings think, were a long way
from the truth, and _not on the road to it_.

Finally, I wish to say that, although the changes proposed in
the conception of mental development have been suggested somewhat
fragmentarily and in various connections, that has not been done because
I think them unimportant. On the contrary, I think them of the utmost
importance. I believe that our best service has been to show that
animal intellection is made up of a lot of specific connections, whose
elements are restricted to them, and which subserve practical ends
_directly_, and to homologize it with the intellection involved in such
human associations as regulate the conduct of a man playing tennis. The
fundamental phenomenon which I find presented in animal consciousness is
one which can harden into inherited connections and reflexes, on the one
hand, and thus connect naturally with a host of the phenomena of animal
life; on the other hand, it emphasizes the fact that our mental life has
grown up as a mediation between stimulus and reaction. The old view of
human consciousness is that it is built up out of elementary sensations,
that very minute bits of consciousness come first and gradually get built
up into the complex web. It looks for the beginnings of consciousness to
_little_ feelings. This our view abolishes and declares that the progress
is not from little and simple to big and complicated, but from direct
connections to indirect connections in which a stock of isolated elements
plays a part, is from ‘pure experience’ or undifferentiated feelings, to
discrimination, on the one hand, to generalizations, abstractions, on
the other. If, as seems probable, the primates display a vast increase
of associations, and a stock of free-swimming ideas, our view gives to
the line of descent a meaning which it never could have so long as the
question was the vague one of more or less ‘intelligence.’ It will,
I hope, when supported by an investigation of the mental life of the
primates and of the period in child life when these directly practical
associations become overgrown by a rapid luxuriance of free ideas,
show us the real history of the origin of human faculty. It turns out
apparently that a modest study of the facts of association in animals has
given us a working hypothesis for a comparative psychology.

CHAPTER III

THE INSTINCTIVE REACTIONS OF YOUNG CHICKS[18]

The data to be presented in this article were obtained in the course of
a series of experiments conducted in connection with the psychological
laboratory of Harvard University during the year 1896-1897. About sixty
chicks were used as subjects. In general their experiences were entirely
under my control from birth. Where this was not true, the conditions of
their life previous to the experiments were known, and were such as would
have had no influence in determining the quality of their reactions in
the particular experiments to which they were subjected. It is not worth
while to recount the means taken so to regulate the chick’s environment
that his experience along certain lines should be in its entirety known
to the observer and that consequently his inherited abilities could be
surely differentiated. The nature of the experiments will, in most cases,
be such that little suspicion of the influence of education by experience
will be possible. In the other cases I will mention the particular means
then taken to prevent such influence.

Some of my first experiments were on color vision in chicks from 18 to
30 hours old, just old enough to move about readily and to be hungry. On
backgrounds of white and black cardboard were pasted pieces of colored
paper about 2 mm. square. On each background there were six of these
pieces,—one each of yellow, red, orange, green, blue and black (on the
white ground) or white (on the black). They were in a row about half an
inch apart. The chicks had been in darkness for all but three or four
hours of their life so far. During those few hours the incubator had been
illuminated and the chicks had that much chance to learn color.

The eight chicks were put, one at a time, on the sheet of cardboard
facing the colored spots. Count was kept of the number of times that they
pecked at each spot and, of course, they were watched to see whether they
would peck at all at random. In the experiments with the white background
all the colors were reacted to (_i.e._ pecked at) except black (but the
letters on a newspaper were pecked at by the same chicks the same day).
One of the chicks pecked at all five, one at four, three at three, one
at two and one at yellow only. These differences are due probably to
accidental position or movements. Taking the sums of the reactions to
each color-spot we get the following table:—

=======+================+=========================
|TIMES REACTED TO|TOTAL NUMBER OF PECKS[19]
-------+----------------+-------------------------
Red | 12 | 31
Yellow | 9 | 21
Orange | 6 | 34
Green | 5 | 11
Blue | 1 | 3
=======+================+=========================

I should attach no importance whatever to the quantitative estimate given
in the table. The only fact of value so far is the evidence that from
the first the chick reacts to all colors. In no case was there any random
pecking at the white surface of the cardboard.

On a black background the same chicks reacted to all the colors.

II is a table of the results.

=======+================+=====================
|TIMES REACTED TO|TOTAL NUMBER OF PECKS
-------+----------------+---------------------
White | 6 | 19
Blue | 4 | 11
Red | 4 | 8
Green | 4 | 4
Orange | 2 | 7
Yellow | 2 | 4
-------+----------------+---------------------

In other experiments chicks were tried with green spots on a red ground,
red spots on a green ground, yellow spots on an orange ground, green
spots on a blue ground, and black spots on a white ground. All were
reacted to. Thus, what is apparently a long and arduous task to the
child is heredity’s gift to the chick. It is conceivable, though to me
incredible, that what the chick reacts to is not the color, but the very
minute elevation of the spot. My spots were made so that they were only
the thickness of thin paper above pasteboard. Any one who cares to resort
to the theory that this elevation caused the reaction can settle the case
by using color-spots absolutely level with the surface.[20]

INSTINCTIVE REACTIONS TO DISTANCE, DIRECTION, SIZE, ETC.

I have purposely chosen this awkward heading rather than the simple
one, Space-Perception, because I do not wish to imply that there is in
the young chick such consciousness of space-facts as there is in human
beings. All that will be shown here is that he reacts appropriately in
the presence of space-facts, reacts in a fashion which would in the case
of a man go with genuine perception of space.

If one puts a chick on top of a box in sight of his fellows below, the
chick will regulate his conduct by the height of the box. To be definite,
we may take the average chick of about 95 hours. If the height is less
than 10 inches, he will jump down as soon as you put him up. At 16 inches
he will jump in from 5 seconds to 3 or 4 minutes. At 22 inches he will
still jump down, but after more hesitation. At 27½ inches 6 chicks out
of eight at this age jumped within 5 minutes. At 39 inches the chick
_will NOT jump down_. The numerical values given here would, of course,
vary with the health, development, hunger and degree of lonesomeness of
the chick. All that they are supposed to show is that at any given age
the chick without experience of heights regulates his conduct rather
accurately in accord with the space-fact of distance which confronts
him. The chick does not peck at objects remote from him, does not, for
instance, confuse a bird a score of feet away with a fly near by, or try
to get the moon inside his bill. Moreover, he reacts in pecking with
considerable accuracy at the very start. Lloyd Morgan has noted that in
his very first efforts the chick often fails to seize the object, though
he hits it, and on this ground has denied the perfection of the instinct.
But, as a matter of fact, the pecking reaction may be as perfect at birth
as it is after 10 or 12 days’ experience. It certainly is not perfect
then. I took nine chicks from 10 to 14 days old and placed them one at
a time on a clear surface over which were scattered grains of cracked
wheat (the food they had been eating in this same way for a week) and
watched the accuracy of their pecking. Out of 214 objects pecked at, 159
were seized, 55 _were not_. Out of the 159 that were seized, _only_ 116
were seized on the first peck, 25 on the second, 16 on the third, and the
remaining two on the fourth. Of the 55 that were not successfully seized,
31 were pecked at only once, 10 twice, 10 three times, 3 four times and
1 five times. I fancy one would find that adult fowls would show by no
means a perfect record. So long as chicks with ten days’ experience fail
to seize on the first trial 45 per cent of the time, it is hardly fair to
argue against the perfection of the instinct on the ground of failures to
seize during the first day.

The chick’s practical appreciation of space-facts is seen further in his
attempts to escape when confined. Put chicks only twenty or thirty hours
old in a box with walls three or four inches high and they will react to
the perpendicularity of the confining walls by trying to jump over them.
In fact, in the ways he moves, the directions he takes and the objects he
reacts to, the chicken has prior to experience the power of appropriate
reaction to colors and facts of all three dimensions.

INSTINCTIVE MUSCULAR COÖRDINATIONS

In the acts already described we see fitting coördinations at work in
the chick’s reactions to space-facts. A few more samples may be given.
In jumping down from heights the chick does not walk off or fall off
(save rarely), but jumps off. He meets the situation “loneliness on a
small eminence” by walking around the edge and peering down; he meets
the situation “sight of fellow chicks below” by (after an amount of
hesitation varying roughly with the height) jumping off, holding his
stubby wings out and keeping right side up. He lands on his feet almost
every time and generally very cleverly. A four days’ chick will jump down
a distance eight times his own height without hurting himself a bit. If
one takes a chick two or three weeks old who has never had a chance to
jump up or down, and puts him in a box with walls three times the height
of the chick’s back, he will find that the chick will jump, or rather
fly, nearly, if not quite, over the wall, flapping his wings lustily
and holding on to the edge with his neck while he clambers over. Chicks
one day old will, in about 57 per cent of the cases, balance themselves
for five or six seconds when placed on a stiff perch. If eight or nine
days old, they will, though never before on any perch or anything like
one, balance perfectly for a minute or more. The muscular coördination
required is invoked immediately when the chick feels the situation “feet
on a perch.” The _strength_ is lacking in the first few days. From the
fifth or sixth day on chicks are also able (their ability increases with
age) to balance themselves on a slowly swinging perch.

Another complex coördination is seen in the somewhat remarkable instinct
of swimming. Chicks only a day or two old will, if tossed into a pond,
head straight for the shore and swim rapidly to it. It is impossible to
compare their movements in so doing with those of ducklings, for the
chick is agitated, paddles his feet very fast and swims to get out, not
for swimming’s sake. Dr. Bashford Dean, of Columbia University, has
suggested to me that the movements may not be those of swimming, but only
of running. At all events, they are utterly different from those of an
adult fowl. In the case of the adult there is no vigorous instinct to
strike out toward the shore. The hen may try to fly back into the boat
if it is dropped overboard, and whether dropped in or slung in from the
shore, will float about aimlessly for a while and only very slowly reach
the shore. The movements the chick makes do look to be such as trying to
run in water might lead to, but it is hard to see why a hen shouldn’t run
to get out of cold water as well as a chick. If, on the other hand, the
actions of the chick are due to a real swimming instinct, it is easy to
see that, being unused, the instinct might wane as the animal grew up.

Such instinctive coördinations as these, together with the walking,
running, preening of feathers, stretching out of leg backward, scratching
the head, etc., noted by other observers, make the infant chick a very
interesting contrast to the infant man. That the helplessness of the
child is a sacrifice to plasticity, instability and consequent power to
develop we all know; but one begins to realize how much of a sacrifice
when one sees what twenty-one days of embryonic life do for the chick
brain. And one cannot help wondering whether some of the space-perception
we trace to experience, some of the coördinations which we attribute to
a gradual development from random, accidentally caused movements may not
be more or less definitely provided for by the child’s inherited brain
structure. Walking has been found to be instinctive; why not other things?

INSTINCTIVE EMOTIONAL REACTIONS

The only experiments to which I wish to refer at length under this
heading are some concerning the chick’s instinctive fears. Before
describing them, it may be well to mention their general bearing on
the results obtained by Spalding and Morgan. They corroborate Morgan’s
decision that no well-defined specific fears are present; that the fears
of young chicks are of strange moving objects in general, shock in
general, strange sounds in general. On the other hand, no such general
disturbances of the chick’s environment led to such well-marked reactions
as Spalding described. And so when Morgan thinks that such behavior as
Spalding witnessed on the part of the chick that heard the hawk’s cry
demands for its explanation nothing more than a general fear of strange
sounds, my experiments do not allow me to agree with him. If Spalding
really saw the conduct which he says the chick exhibited on the third
day of its life in the presence of man, and later at the stimulus of
the sight or sound of the hawk, there are specific reactions. For the
running, crouching, silence, quivering, etc., that one gets by yelling,
banging doors, tormenting a violin, throwing hats, bottles, or brushes
at the chick is never anything like so pronounced and never lasts one
tenth as long as it did with Spalding’s chicks. But, as to the fear of
man, Spalding must have been deluded. In the second, third and fourth
days there is no such reaction to the sight of man as he thought he saw.
Miss Hattie E. Hunt, in the _American Journal of Psychology_, Vol. IX.,
No. 1, asserts that there is no instinctive fear of a cat. Morgan did
not find such. I myself put chicks of 2, 5, 9 and 17 days (different
individuals each time, 11 in all) in the presence of a cat. They showed
no fear, but went on eating as if there was nothing about. The cat was
still, or only slowly moving. I further put a young kitten (eight inches
long) in the pen with chicks. He felt of them with his paw, and walked
around among them for five or ten minutes, yet they showed no fear (nor
did he instinctively attack them). If, however, you let a cat jump at
chicks in real earnest, they will not stay to be eaten, but will manifest
fear—at least chicks three to four weeks old will. I did not try this
experiment with chicks at different ages, because it seemed rather cruel
and degrading to the experimenter. When in the case of the older chicks
nature happened to make the experiment, it was hard to decide whether
there was more violent fear of the jumping cat than there was when one
threw a basket or football into the pen. There was not very much more.

We may now proceed to a brief recital of the facts shown by the
experiments in so far as they are novel. It should be remembered
throughout that in every case chicks of different ages were tested so as
to demonstrate transitory instincts if such existed, _e.g._, the presence
of a fear of flame was tested with chicks 59 and 60, one day old, 30 and
32, two days old, 21 and 22, three days old, 23 and 24, seven days old,
27 and 29, nine days old, 16 and 19, eleven days old, and so on up to
twenty-days-old chicks. By thus using different subjects at each trial
one, of course, eliminates any influence of experience.

The first notable fact is that there develops in the first month a
general fear of novel objects in motion. For four or five days there
seems to be no such. You may throw a hat or slipper or shaving mug at a
chick of that age, and he will do no more than get out of the way of it.
But a twenty-five-days-old chick will generally chirr, run and crouch for
five or ten seconds. My records show this sort of thing beginning about
the tenth day, but it is about ten days more before it is very marked.
In general, also, the reaction is more pronounced if many chicks are
together, and is then displayed earlier (only two at a time were taken
in the experiments the results of which have just been quoted). Thus the
reaction is to some degree a social performance, the presence of other
chicks combining with the strange object to increase the vigor of the
reaction. Chicks ordinarily scatter apart when they thus run from an
object.

One witnesses a similar gradual growth of the fear of man (not as such
probably, but merely as a large moving object). For four or five days
you can jump at the chick, grab at it with your hands, etc., without
disturbing it in the least. A chick twenty days old, however, although he
has never been touched or approached by a man, and in some cases never
seen one except as the daily bringer of food, and has never been in any
way injured by any large moving object of any sort, will run from you if
you try to catch him or even get very near him. There is, however, even
then, nothing like the utter fear described by Spalding.

Up to thirty days there was no fear of a mocking bird into whose cage
the chicks were put, no fear of a stuffed hawk or a stuffed owl (kept
stationary). Chicks try to escape from water (even though warmed to the
temperature of their bodies) from the very first. Up to forty days there
appears no marked waning of the instinct. They did not show any emotional
reaction to the flame produced by six candles stuck closely together.
From the start they react instinctively to confinement, to loneliness,
to bodily restraint, but their feeling in these cases would better be
called discomfort than fear. From the 10th or 12th to the 20th day, and
probably later and very possibly earlier, one notices in chicks a general
avoidance of open places. Turn them out in your study and they will not
go out into the middle of the room, but will cling to the edges, go under
chairs, around table legs and along the walls. One sees nothing of the
sort up through the fourth day. Some experiments with feeding hive bees
to the chicks are interesting in connection with the following statement
by Lloyd Morgan: “One of my chicks, three or four days old, snapped up
a hive bee and ran off with it. Then he dropped it, shook his head much
and often, and wiped his bill repeatedly. I do not think he had been
stung: _probably he tasted the poison_” (‘Introduction to Comparative
Psychology,’ p. 86). I fed seven bees apiece to three chicks from ten to
twenty days old. _They ate them all greedily_, first smashing them down
on the ground violently in a rather dexterous manner. Apparently this
method of treatment is peculiar to the object. Chicks _three_ days old
did not eat the bees. Some pecked at them, but none would snap them up,
and when the bee approached, they sometimes sounded the danger note.

Finally an account may be given of the reaction of chicks at different
ages, up to twenty-six days, to loud sounds. These were the sounds made
by clapping the hands, slamming a door, whistling sharply, banging a tin
pan on the floor, mewing like a cat, playing a violin, thumping a coal
scuttle with a shovel, etc. Two chicks were together in each experiment.
Three fourths of the times no effect was produced. On the other occasions
there was some running or crouching or, at least, starting to run or
crouch; but, as was said, nothing like what Spalding reports as the
reaction to the ‘cheep’ of the hawk. It is interesting to notice that
the two most emphatic reactions were to the imitation mew. One time a
chick ran wildly, chirring, and then crouched and stayed still until I
had counted 105. The other time a chick crouched and stayed still until I
counted 40. But the other chick with them did not; and in a dozen other
cases the ‘meaw’ had no effect.

I think that the main interest of most of these experiments is the proof
they afford that instinctive reactions are not necessarily definite,
perfectly appropriate and unvarying responses to accurately sensed and,
so to speak, estimated stimuli. The old notion that instinct was a
God-given substitute for reason left us an unhappy legacy in the shape of
the tendency to think of all inherited powers of reaction as definite
particular acts invariably done in the presence of certain equally
definite situations. Such an act as the spider’s web-spinning might be
a stock example. Of course, there are many such instinctive reactions
in which a well-defined act follows a well-defined stimulus with the
regularity and precision with which the needle approaches the magnet.
But our experiments show that there are acts just as truly instinctive,
depending in just the same way on inherited brain-structure, but
characterized by being vague, irregular, and to some extent dissimilar,
reactions to vague, complex situations.

The same stimulus doesn’t always produce just the same effect, doesn’t
produce precisely the same effect in all individuals. The chick’s
brain is evidently prepared in a general way to react more or less
appropriately to certain stimuli, and these reactions are among the most
important of its instincts or inherited functions. But yet one cannot
take these and find them always and everywhere. This helps us further to
realize the danger of supposing that in observation of animals you can
depend on a rigid uniformity. One would never suppose because one boy
twirled his thumb when asked a question that all boys of that age did.
But naturalists have been ready to believe that because one young animal
made a certain response to a certain stimulus, the thing was an instinct
common to all in precisely that same form. But a loud sound may make one
chick run, another crouch, another give the danger call, and another do
nothing whatever.

In closing this article I may speak of one instinct which shows itself
clearly from at least as early as the sixth day, which is preparatory
to the duties of adult life and of no other use whatsoever. It is
interesting in connection with the general matter of animal play. The
phenomenon is as follows: The chicks are feeding quietly when suddenly
two chicks rush at each other, face each other a moment and then go about
their business. This thing keeps up and grows into the ordinary combat of
roosters. It is rather a puzzle on any theory that an instinct needed so
late should begin to develop so early.

CHAPTER IV

A NOTE ON THE PSYCHOLOGY OF FISHES[21]

Numerous facts witness in a vague way to the ability of fishes to profit
by experience and fit their behavior to situations unprovided for by
their innate nervous equipment. All the phenomena shown by fishes as a
result of taming are, of course, of this sort. But such facts have not
been exact enough to make clear the mental or nervous processes involved
in such behavior, or simple enough to be available as demonstrations
of such processes. It seemed desirable to obtain evidence which should
demonstrate both the fact and the process of learning or intelligent
activity in the case of fishes and demonstrate them so readily that any
student could possess the evidence first hand.

Through the kindness of the officials of the United States Fish
Commission at Woods Holl, especially of the director, Dr. Bumpus, I was
able to test the efficiency of some simple experiments directed toward
this end. The common Fundulus was chosen as a convenient subject, and
also because of the neurological interest attaching to the formation of
intelligent habits by a vertebrate whose forebrain lacks a cortex.

The fishes studied were kept in an aquarium (about 4 feet long by 2 feet
wide, with a water depth of about 9 inches) represented by Fig. 24. The
space at one end, as represented by the lines in the figure, was shaded
from the sun by a cover, and all food was dropped in at this end. Along
each side of the aquarium were fastened simple pairs of cleats, allowing
the experimenter to put across it partitions of wood, glass or wire
screening. One of these in position is shown in the figure by the dotted
line. These partitions were made each with an opening, as shown in Fig.
25. If now we cause the fish to leave his shady corner and swim up to
the sunny end by putting a slide (without any opening) in behind him at
_D_ and moving it gently from _D_ to _A_ and then place, say slide _I_,
across the aquarium at 1, we shall have a chance to observe the animal’s
behavior to good purpose.

[Illustration: FIG. 24.]

[Illustration: FIG. 25.]

This fish dislikes the sunlight and tries to get back to _D_. He reacts
to the situation in which he finds himself by swimming against the
screen, bumping against it here and there along the bottom. He may stop
and remain still for a while. He will occasionally rise up toward the
top of the water, especially while swimming up and down the length of
the screen. When he happens to rise up to the top at the right-hand end,
he has a clear path in front of him and swims to _D_ and feels more
comfortable.

If, after he has enjoyed the shade fifteen minutes or more, you again
confine him in _A_, and keep on doing so six or eight times a day for a
day or so, you will find that he swims against the screen less and less,
swims up and down along it fewer and fewer times, stays still less and
less, until finally his only act is to go to the right-hand side, rise
up, and swim out. In correspondence with this change in behavior you will
find a very marked decrease in the time he takes to escape. The fish
has clearly profited by his experience and modified his conduct to suit
a situation for which his innate nervous equipment did not definitely
provide. He has, in common language, _learned_ to get out.

This particular experiment was repeated with a number of individuals.
Another experiment was made, using three slides, _II_, _III_, and
another, requiring the fish to find his way from _A_ to _B_, _B_ to _C_,
and from _C_ to _D_. The results of these and still others show exactly
the same general mental process as does the one described—a process which
I have discussed at length elsewhere.

Whatever interest there is in the demonstration in the case of the
bony fishes of the same process which accounts for so much of the
behavior of the higher vertebrates may be left to the neurologists.
The value of the experiment, if any, to most students will perhaps
be the extreme simplicity of the method, the ease of administering
it, and its possibilities. By using long aquaria, one can study the
formation of very complex series of acts and see to what extent any
fish can carry the formation of such series. By proper arrangements the
delicacy of discrimination of the fish in any respect may be tested.
The artificiality of the surroundings may, of course, be avoided when
desirable.

CHAPTER V

THE MENTAL LIFE OF THE MONKEYS; AN EXPERIMENTAL STUDY[22]

The literary form of this monograph is not at all satisfactory to its
author. Compelled by practical considerations to present the facts
in a limited space, he has found it necessary to omit explanation,
illustration and many rhetorical aids to clearness and emphasis. For the
same reason detailed accounts of the administration of the experiments
have not always been given. In many places theoretical matters are
discussed with a curtness that savors of dogmatism. In general when a
theoretical point has appeared justified by the evidence given, I have,
to economize space, withheld further evidence.

There is, however, to some extent a real fitness in the lack of
clearness, completeness and finish in the monograph. For the behavior of
the monkeys, by virtue of their inconstant attention, decided variability
of performance, and generally aimless, unforetellable conduct would be
falsely represented in any clean-cut, unambiguous, emphatic exposition.
The most striking testimony to the mental advance of the monkeys over
the dogs and cats is given by the difficulty of making clear emphatic
statements about them.

INTRODUCTION

The work to be described in this paper is a direct continuation of
the work done by the author in 1897-1898 and described in Monograph
Supplement No. 8 of the _Psychological Review_ under the heading, ‘Animal
Intelligence; an Experimental Study of the Associative Processes in
Animals.’[23] This monograph affords by far the best introduction to the
present discussion, and I shall therefore assume an acquaintance with it
on the part of my readers.

It will be remembered that evidence was there given that ordinary
mammals, barring the primates, did not infer or compare, did not imitate
in the sense of ‘learning to do an act from seeing it done,’ did not
learn various simple acts from being put through them, showed no signs
of having in connection with the bulk of their performances any mental
images. Their method of learning seemed to be the gradual selection of
certain acts in certain situations by reason of the satisfaction they
brought. Quantitative estimates of this gradualness were given for a
number of dogs and cats. Nothing has appeared since the ‘Experimental
Study’ to negate any of these conclusions in the author’s mind. The
work of Kline and Small[24] on rodents shows the same general aspect of
mammalian mentality.

Adult human beings who are not notably deficient in mental functions,
at least all such as psychologists have observed, possess a large stock
of images and memories. The sight of a chair, for example, may call up
in their minds a picture of the person who usually sits in it, or the
sound of his name. The sound of a bell may call up the idea of dinner.
The outside world also is to them in large part a multitude of definite
percepts. They feel the environment as trees, sticks, stones, chairs,
tables, letters, words, etc. I have called such definite presentations
‘free ideas’ to distinguish them from the vague presentations such as
atmospheric pressure, the feeling of malaise, of the position of one’s
body when falling, etc. It is such ‘free ideas’ which compose the
substance of thought and which lead us to perhaps the majority of the
different acts we perform, though we do, of course, react to the vaguer
sort as well. I saw definitely in writing the last sentence the words
‘majority of the different acts’ and thought ‘we perform’ and so wrote
it. I see a bill and so take check book and pen and write. I think of the
cold outside and so put on an overcoat. This mental function ‘having free
ideas,’ gives the possibility of learning to meet situations properly
by thinking about them, by being reminded of some property of the fact
before us or some element therein.

We can divide all learning into (1) _learning by trial and accidental
success_, by the strengthening of the connections between the
sense-impressions representing the situation and the acts—or impulses and
acts—representing our successful response to it and by the inhibition
of similar connections with unsuccessful responses; (2) _learning by
imitation_, where the mere performance by another of a certain act in a
certain situation leads us to do the same; and (3) _learning by ideas_,
where the situation calls up some idea (or ideas) which then arouses the
act or in some way modifies it.

The last method of learning has obviously been the means of practically
all the advances in civilization. The evidence quoted a paragraph or so
back from the Experimental Study shows the typical mammalian mind to be
one which rarely or never learns in this fashion. The present study of
the primates has been a comparative study with two main questions in
view: (1) How do the monkeys vary from the other mammals in the general
mental functions revealed by their methods of learning? (2) How do they,
on the other hand, vary from adult civilized human beings?

The experiments to be described seem, however, to be of value apart from
the possibility of settling crucial questions by means of the evidence
they give. To obtain exact accounts of what animals can learn by their
own unaided efforts, by the example of their fellows or by the tuition of
a trainer, and of how and how fast they learn in each case, seems highly
desirable. I shall present the results in the manner which fits their
consideration as arguments for or against some general hypotheses, but
the naturalist or psychologist lacking the genetic interest may find an
interest in them at their face value. I shall confine myself mainly to
questions concerning the method of learning of the primates, and will
discuss their sense-powers and unlearned reactions or instincts only in
so far as is necessary to its comprehension.

It has been impossible for the author to make helpful use of the
anecdotes and observations of naturalists and miscellaneous writers
concerning monkey intelligence. The objections to such data pointed out
in Chapter II, pp. 22-26, hold here. Moreover it is not practicable to
sift out the true from the false or to interpret these random instances
of animal behavior even if assuredly true. In the study of animal life
the part is only clear in the light of the whole, and it is wiser to
limit conclusions to such as are drawn from the constant and systematic
study of a number of animals during a fairly long time. After a large
enough body of such evidence has been accumulated we may be able to
interpret random observations.

The subjects of the experiments were three South American monkeys of the
genus _Cebus_. At the time of beginning the experiment No. 1 was about
half grown, No. 2 was about one fourth full size and No. 3 was about half
grown. No. 1 was under observation from November, 1899, to February,
1900; No. 2 and No. 3 from October, 1900, to February, 1901. No. 1 was
during the period of experimentation decidedly tame, showing no fear
whatever of my presence and little fear at being handled. He would handle
and climb over me with no hesitation. No. 2 was timid, did not allow
handling, but showed no fear of my presence and no phenomena that would
differentiate his behavior in the experiments discussed from that of No.
1, save much greater caution in all respects. No. 3 also showed no fear
at my presence. Any special individual traits that are of importance in
connection with any of the observations will be mentioned in their proper
places. No. 1 was kept until June, 1900, in my study in a cage 3 by 6 by
6 feet, and was left in the country till October, 1900. From October,
1900, all three were kept in a room 8 by 9 feet, in cages 6 feet tall by
3 long by 2.6 wide for Nos. 1 and 2, 3 feet by 3 feet by 20 inches for
No. 3. I studied their behavior in learning to get into boxes, the doors
to which could be opened by operating some mechanical contrivance, in
learning to obtain food by other simple acts, in learning to discriminate
between two signals, that is, to respond to each by a different act, and
in their general life.

Following the order of the ‘Animal Intelligence,’ I shall first recount
the observations of the way the monkeys learned, solely by their own
unaided efforts, to operate simple mechanical contrivances.

Besides a number of boxes such as were used with the dogs and cats (see
illustration on p. 30), I tried a variety of arrangements which could
be set up beside a cage, and which would, when some simple mechanism was
set in action, throw a bit of food into the cage. Figure 26 shows one of
these. See description of QQ (ff) on page 182.

[Illustration: FIG. 26. _A_, loop; _BB_, lever, pivoted at _M_. A bit of
food put in front of _C_ would be thrown down the chute _DDD_ when _A_
was released.]

APPARATUS

The different mechanisms which I used were the following:—

Box BB (O at back) was about 20 by 14 by 12 inches with a door in the
front which was held by a bolt to which was tied a string. This string
ran up the front of the box outside, over a pulley, across the top, and
over another pulley down into the box, where it ended in a loop of wire.

Box MM (bolt) was the same as BB but with no string and loop attachment
to the bolt.

Box CC (single bar) was a box of the same size as BB. The door was held
by a bar about 3 by 1 by 5 inches which swung on a nail at the left side.

Box CCC (double bar) was CC with a second similar bar on the right side
of the door.

Box NN (hook) was a box about the size of BB with its door held by an
ordinary hook on the left side which hooked through an eyelet screwed
into the door.

Box NNN was NN with the hook on the right instead of the left side.

Box NNNN was box NN with two hooks, one on each side.

Apparatus OO (string box) consisted of a square box tied to a string,
which formed a loop running over a pulley by the cage and a pulley
outside, so that pulling on the under string would bring the box to the
cage. In each experiment the box was first pulled back to a distance of 2
feet 3 inches from the cage, and a piece of banana put in it. The monkey
could, of course, secure the banana by pulling the box near enough.

Apparatus OOO was the same as OO, with the box tied to the upper string,
so that the upper string had to be pulled instead of the lower.

Box PP was about the size of BB. Its door was held by a large string
securely fastened at the right, passing across the front of the door and
ending in a loop which was put over a nail on the box at the left of the
door. By pulling the string off the nail the door could be opened.

Box RR (wood plug) was a box about the size of BB. The door was held by
a string at its top, which passed up over the front and top to the rear,
where it was fastened to a wooden plug which was inserted in a hole in
the top of the box. When the plug was pulled out of the hole, the door
would fall open.

Box SS (triple; wood-plug, hook and bar) was a box about the size of BB.
To open the door, a bar had to be pushed around, a hook unhooked and a
plug removed from a hole in the top of the box.

Box TT (nail plug) was 14 by 10 by 10 inches with a door 5.5 by 10 on
the right side of the front, the rest of the front being barred up. The
door was hinged at the bottom and fastened at its top to a wire which
was fastened to a nail 2.5 inches long, which, when inserted in a hole
0.25 inches in diameter at the back of the top of the box, held the door
closed. By drawing out this nail and pulling the door the animal could
open the door.

Box VV (plug at side) was a box about 18 by 10 by 10, the door held by
a plug passing through a hole in the side of the box. When the plug was
pulled out, the door could be pushed inward.

Box W (loop) was 17 by 10 by 10 inches with a door 5 by 9 at the left
side of its front hinged at the bottom. The door was prevented from
falling inward by a wire stretched behind it. It was prevented from
falling outward by a wire firmly fastened at the right side and held by a
loop over a nail at the left. By pulling the loop outward and to the left
it could be freed from the nail. The door could then be pulled open.

Box WW (bar inside) was 16 by 14 by 10 inches with a door 4 by 11 at the
left of its front hinged at the bottom. The door could be pushed in or
pulled out when a bar on its inside was lifted out of a latch. The bar
was accessible from the outside through an opening in the front of the
box. It had to be lifted to a height of 1.5 inches (an angle of about
30°).

Box XX (bar outside) was about 13 by 11 by 10 inches with a door 7 by
8 on the left side of the front. The door was held in place by a bar
swinging on a nail at the top, with its other end resting in a latch at
the left side of the box. By pushing this up through an angle of 45° the
door could be opened.

Box YY (push bar) was a box 16 by 8 by 12 inches with a door at the left
of its front. The door was held by a brass bar which swung down in front
of an L-shaped piece of steel fastened to the inside of the door. This
brass bar was hung on a pivot at its center and the other end attached
to a bar of wood; the other end of this bar projected through a hole at
the right side of the box. By pushing this bar in about an inch the door
could be opened.

Box LL (triple; nail plug, hook and bar) was a box 10 by 10 by 13 with a
door 3 by 8.5 at the left side. The door could be opened only after (1) a
nail plug had been removed from a hole in the back of the top of the box
as in TT, (2) a hook in the door had been unhooked, and (3) a bar on the
left side had been turned from a horizontal to a vertical position.

Box Alpha (catch at back) was 11 by 10 by 15 with the door (4 by 4) in
the left side of its front. The door was held by a bolt, which, when let
down, held in a catch on the inside of the door. A string fastened to the
bolt ran across to the back of the box and through a hole to the outside.
There it ended in a piece of wood 2.5 by 1 by .25 inches. When this piece
of wood was pulled, the bolt went up and the door fell open.

Box Beta was the same as NN except in size. It was 10 by 10 by 13 inches.

Box KK (triple; bolt, side plug, and knob) was a box 16 by 9 by 11 with
a door at the left side of the front. The door was held by a bolt on the
right side, a wooden plug stuck through a hole in the box on its left
side and a nail which held in a catch at its top. This nail was fastened
to a wooden knob (1 by 5 by .375) which lay in a depression at the top of
the box. Only when the bolt had been drawn and the plug and knob pulled,
could the door be opened.

Box Gamma (wind) was 10 by 10 by 13 inches with its door held by a wire
fastened at the top and wound three times about a screw eye in the top of
the box. By unwinding the wire the door could be opened.

Box Delta (push back) was 12 by 11 by 10 inches. Its door was held by
a wooden bar projecting from the right two inches in front of it. This
bar was so arranged that it could be pushed or pulled toward the right,
allowing the door to fall open. It could not be swung up or down.

Box Epsilon (lever or push down) was 12 by 9 by 5 inches. At the right
side of its front was a hole ½ inch broad by 1½ inches up and down.
Across this hole on the inside of the box was a strip of brass, the end
of one bar of a lever. If this strip was depressed ⅛ of an inch, the door
at the extreme left would be opened by a spring.

Box Zeta (side plug) was 12 by 11 by 10 inches. Its door was held by a
round bar of wood put through a hoop of steel at the left side of the
box. This bar was loose and could easily be pulled out, allowing the door
to be opened.

Box Theta was the same as KK except that the door could be opened as soon
as the bolt alone was pulled or pushed up.

Box Eta was like Alpha save that the object at the back of the box to be
pulled was a brass ring.

Apparatus QQ (chute) consisted of a lever mechanism so arranged that
by pushing in a bar of wood ¼ to ½ an inch, a piece of banana would be
thrown down a chute into the cage. The apparatus was placed outside the
cage in such a way that it could be easily reached by the monkey’s arm
through the wire netting.

QQ (a) was of the same general plan. By turning a handle through 270°
food could be obtained.

QQ (b) was like QQ (a) except that 2½ full revolutions of the handle in
one direction were necessary to cause the food to drop down.

QQ (c) was a chute apparatus so arranged as to work when a nail was
pulled out of a hole.

QQ (d) was arranged to work at a sharp pull upon a brass ring hanging to
it.

QQ (e) was arranged to work when a hook was unhooked.

QQ (f) was arranged to work when a loop at the end of a string was pulled
off from a nail.

QQ (ff) was QQ (f) with a stiff wire loop instead of a loop of string.

EXPERIMENTS ON THE ABILITIES OF THE MONKEYS TO LEARN WITHOUT TUITION

I will describe a few of the experiments with No. 1 as samples and then
present the rest in the form of a table. No. 1 was tried first in BB (O
at back) on January 17, 1900, being _put inside_. He opened the box by
pulling up the string just above the bolt. His times were .05, 1.38,
6.00, 1.00, .10, .05, .05. He was not easily handled at this time, so I
changed the experiment to the form adopted in future experiments. I put
the food inside and left the animal to open the door from the outside. He
pulled the string up within 10 seconds each time out of 10 trials.

I then tried him in MM (bolt). He failed in 15. I then (January 18th)
tried him in CC (single bar outside). He got in in 36.00 minutes; he did
not succeed a second time that night, but in the morning the box was
open. His times thenceforth were 20, 10, 16, 25 and on January 19th, 40,
5, 12, 8, 5, 5, 5 seconds.

I then tried him (January 21, 1900) in CCC (double bar). He did it at
first by pushing the old bar and then pulling at the door until he worked
the second bar gradually around. Later he at times pushed the second
bar. The times taken are shown in the time-curve. I then (January 25th)
tried him in NN (hook). See time-curves on page 185. I then (January
27th) tried him in NNN (hook on other side). He opened it in 6, 12 and 4
seconds in the first three trials. I then (20 minutes later) tried him
with NNNN (double hook). He opened the door in 12, 10, 6 and 6 seconds. I
then (January 27th) tried him with PP (string across). He failed in 10.
I then (February 21st) tried him with apparatus OO (string box). For his
progress as shown by the times taken see the time-curve. His progress is
also shown in the decrease of the useless pullings at the wrong string.
There were none in the 9th trial, 14th, 15th, 16th, 18th, 24th, and
following trials.

No. 1 was then (February 24th) tried with OOO (string box with box on
upper string). No. 1 succeeded in 2.20, then failed in 10.00. The rest of
the experiment will be described under imitation.

He was next tried (March 24th) with apparatus QQ (chute). He failed
in 10.00, though he played with the apparatus much of the time. Other
experiments were with box RR (wood-plug) (April 5th). He failed in 10.00.
After he had, in a manner to be described later, come to succeed with RR,
he was tried in box SS (triple; wood-plug, hook and bar) (April 18th);
see time-curve. No more experiments of this nature were tried until
October, 1900.

The rest of the experiments with No. 1 and all those with No. 2 and No.
3 may best be enumerated in the form of a table. (See Table 9 on page
187.) It will show briefly the range of performances which the unaided
efforts of the animals can cope with. It will also give the order in
which each animal experienced them. F means that the animal failed to
succeed. The figures are minutes and seconds, and represent the time
taken in the first trial or the total time taken without success where
there is an F. In cases where the animal failed in say 10 minutes, but in
a later trial succeeded, say in 2.40, the record will be 2.40 after 10 F.
There are separate columns for all three animals, headed No. 1, No. 2 and
No. 3. Im. stands for a practically immediate success.

The curves on pages 185 and 186 (Figs. 27 and 28) show the progress of
the formation of the associations in those cases where the animal was
given repeated trials, with, however, nothing to guide him but his own
unaided efforts. Each millimeter on the abscissa represents one trial
and each millimeter on the ordinate represents 10 seconds, the ordinates
representing the time taken by the animal to open the box. A break in
the curve, or an absence of the curve at the beginning of the base-line
represents cases where the animal failed in 10 minutes or took a very
long time to get out.

[Illustration: FIG. 27.]

[Illustration: FIG. 28.]

In discussing these facts we may first of all clear our way of one
popular explanation, that this learning was due to ‘reasoning.’ If
we use the word reasoning in its technical psychological meaning as
the function of reaching conclusions by the perception of relations,
comparison and inference, if we think of the mental content involved as
feelings of relation, perceptions of similarity, general and abstract
notions and judgments, we find no evidence of reasoning in the behavior
of the monkeys toward the mechanisms used. And this fact nullifies the
arguments for reasoning in their case as it did in the case of the
dogs and cats. The argument that successful dealings with mechanical
contrivances imply that the animals reasoned out the properties of the
mechanisms, is destroyed when we find mere selection from their general
instinctive activities sufficient to cause success with bars, hooks,
loops, etc. There is also in the case of the monkeys, as in that of the
other mammals, positive evidence of the absence of any general function
of reasoning. We shall find that at least very many simple acts were not
learned by the monkeys in spite of their having seen me perform them
again and again; that the same holds true of many simple acts which they
saw other monkeys do, or were put through by me. We shall find that after
having abundant opportunity to realize that one signal meant food at the
bottom of the cage and another none, a monkey would not act from the
obvious inference and consistently stay up or go down as the case might
be, but would make errors such as would be natural if he acted under
the growing influence of an association between sense-impression and
impulse or sense-impression and idea, but quite incomprehensible if he
had compared the two signals and made a definite inference. We shall find
that, after experience with several pairs of signals, the monkeys yet
failed, when a new pair was used, to do the obvious thing to a rational
mind; viz., to compare the two, think which meant food, and act on the
knowledge directly.

TABLE 9

-------------------------------+---------------------------------+
| No. 1. |
+-------------+---------+---------+
| |Min. Sec.| |
-------------------------------+-------------+---------+---------+
Box TT (nail plug) |Oct. 19, 1900| 0.40 | |
Box UU (old plug at side) |Oct. 19, 1900| | F 60.00|
Box VV (wire loop) |Oct. 20, 1900| |{ F 10.00|
| | |{ F 10.00|
| | |{ F 10.00|
Box WW (bar inside) |Oct. 20, 1900| | F 10.00|
| | | |
| | | |
| | | |
Box XX (bar outside) |Oct. 23, 1900| im. | after |
| | | [25] |
| | | F 10.00|
Box YY (push bar) |Oct. 30, 1900| 2.00[26]| |
Box Beta (single hook) | | | |
| | | |
| | | |
Box LL (triple; nail plug, |Nov. 4, 1900 |16.00[27]| |
hook and bar outside) | | | |
Box Alpha (catch at back) |Nov. 5, 1900 | .35 | |
Box KK (triple; bolt, side-plug|Nov. 7, 1900 | | F 10.00|
and knob) | | | F 10.00|
Box Theta (bolt at top) |Nov. 19, 1900| | F 10.00|
Box Eta (ring at back) |Dec. 17, 1900| im. | |
App. QQ (push chute) | | | |
Box Gamma (wind) |Jan. 3, 1901 | .20 | |
| | | |
Box Delta (push back) |Jan. 4, 1901 | | F 5.00|
| | | F 5.00|
App. QQ (a) (bar chute) |Jan. 6, 1901 | 8.00 | |
Box Zeta (new side plug) |Jan. 7, 1901 | 1.10 | after |
| | | F 5.00|
App. QQ (b) (2½ revolution | | | |
chute) |Jan. 9, 1901 | 3.00 | |
App. QQ (c) (nail-plug | | | |
chute) |Jan. 11, 1901| | F 5.00|
| | | F 5.00|
Box Epsilon (push down) |Jan. 12, 1901| | F 5.00|
| | | F 10.00|
App. QQ (d) (ring chute) |Jan. 16, 1901| | F 5.00|
| | | F 5.00|
App. QQ (e) (hook chute) | | | |
App. QQ (f) (string chute) |Jan. 17, 1901| | F 5.00|
App. QQ (ff) (string-wire |Jan. 17, 1901| .20 | |
chute) | | | |
-------------------------------+-------------+---------+---------+

-------------------------------+---------------------------------+
| No. 2. |
+-------------+---------+---------+
| |Min. Sec.| |
-------------------------------+-------------+---------+---------+
Box TT (nail plug) |Oct. 21, 1900| 14.10 | |
Box UU (old plug at side) | | | |
Box VV (wire loop) |Oct. 24, 1900| | F 10.00|
|Oct. 25, 1900| | F 10.00|
| | | |
Box WW (bar inside) |Oct. 21, 1900| 5.00 | after|
| | | F 30.00|
| | | |
| | | |
Box XX (bar outside) |Oct. 24, 1900| 3.40 | |
| | | |
| | | |
Box YY (push bar) | | | |
Box Beta (single hook) |Oct. 30, 1900| 9.00 | after|
| | | F 10.00|
| | |and 10.00|
Box LL (triple; nail plug, |Oct. 3, 1900 | 2.00 | |
hook and bar outside) | | | |
Box Alpha (catch at back) |Oct. 5, 1900 | 6.00 | |
Box KK (triple; bolt, side-plug|Oct. 7, 1900 | | F 60.00|
and knob) | | | |
Box Theta (bolt at top) | | | |
Box Eta (ring at back) | | | |
App. QQ (push chute) | | | |
Box Gamma (wind) | | | |
| | | |
Box Delta (push back) | | | |
| | | |
App. QQ (a) (bar chute) | | | |
Box Zeta (new side plug) | | | |
| | | |
App. QQ (b) (2½ revolution | | | |
chute) | | | |
App. QQ (c) (nail-plug | | | |
chute) | | | |
| | | |
Box Epsilon (push down) | | | |
| | | |
App. QQ (d) (ring chute) | | | |
| | | |
App. QQ (e) (hook chute) | | | |
App. QQ (f) (string chute) | | | |
App. QQ (ff) (string-wire | | | |
chute) | | | |
-------------------------------+-------------+---------+---------+

-------------------------------+----------------------------------
| No. 3.
+-------------+---------+----------
| |Min. Sec.|
-------------------------------+-------------+---------+----------
Box TT (nail plug) |Oct. 21, 1900| 36.00 |
Box UU (old plug at side) | | |
Box VV (wire loop) |Oct. 22, 1900| |{ F 10.00
| | |{ F 10.00
| | |{ F 10.00
Box WW (bar inside) |Oct. 22, 1900| |{ F 10.00
|Oct. 24, 1900| |{ F 5.00
| | |{ F 10.00
| | |{ F 15.00
Box XX (bar outside) |Oct. 23, 1900| .30 |
| | |
| | |
Box YY (push bar) | | |
Box Beta (single hook) |Oct. 24, 1900| im. |
| | |
| | |
Box LL (triple; nail plug, |Nov. 3, 1900 | 1.45 |
hook and bar outside) | | |
Box Alpha (catch at back) |Nov. 5, 1900 | |
Box KK (triple; bolt, side-plug|Nov. 7, 1900 | | F 10.00
and knob) | | |
Box Theta (bolt at top) |Jan. 8, 1901 | | F 10.00
Box Eta (ring at back) |Dec. 17, 1900| 4.20 |
App. QQ (push chute) |Dec. 17, 1900| | F 60.00
Box Gamma (wind) |Jan. 4, 1901 | | F 10.00
| | | F 10.00
Box Delta (push back) |Jan. 4, 1901 | 2.10 |after[28]
| | | F 10.00
App. QQ (a) (bar chute) |Jan. 7, 1901 | | F 10.00
Box Zeta (new side plug) |Jan. 8, 1901 | .50 |
| | |
App. QQ (b) (2½ revolution | | |
chute) |Jan. 8, 1901 | | F 10.00
App. QQ (c) (nail-plug | | |
chute) |Jan. 11, 1901| | F 5.00
| | | F 5.00
Box Epsilon (push down) |Jan. 12, 1901| | F 10.00
| | |
App. QQ (d) (ring chute) |Jan. 16, 1901| im. |
| | |
App. QQ (e) (hook chute) |Jan. 16, 1901| | F 5.00
App. QQ (f) (string chute) | | |
App. QQ (ff) (string-wire |Jan. 19, 1901| | F 5.00
chute) | | | F 5.00
-------------------------------+-------------+---------+----------

The methods one has to take to get them to do anything, their general
conduct in becoming tame and in the experiments throughout, confirm
these conclusions. The following particular phenomena are samples of the
many which are inconsistent with the presence of reasoning as a general
function. No. 1 had learned to open a door by pushing a bar around from
a horizontal to a vertical position. The same box was then fitted with
two bars. He turned the first bar round thirteen times before attempting
to push the other bar around. In box LL all three monkeys would in the
early trials do one or two of the acts over and over after they had once
done them. No. 1, who had learned to pull a loop of wire off from a nail,
failed thereafter to pull off a similar loop made of string. No. 1 and
No. 3 had learned to poke their left hands through the cage for me to
take and operate a chute with. It was extremely difficult to get either
of them to put his right hand through or even to let me take it and pull
it through.

A negative answer to the question “Do the monkeys reason?” thus
seems inevitable, but I do not attach to the question an importance
commensurate with the part it has played historically in animal
psychology. For I think it can be shown, and I hope in a later monograph
to show, that reasoning is probably but one secondary result of the
general function of having free ideas in great numbers, one product of a
type of brain which works in great detail, not in gross associations. The
denial of reasoning need not mean, and does not to my mind, any denial
of continuity between animal and human mentality or any denial that the
monkeys are mentally nearer relatives to man than are the other mammals.

So much for supererogatory explanation. Let us now turn to a more
definite and fruitful treatment of these records.

The difference between these records and those of the chicks, cats and
dogs given on pages 39-65 _passim_ is undeniable. Whereas the latter
were practically unanimous, save in the cases of the very easiest
performances, in showing a process of gradual learning by a gradual
elimination of unsuccessful movements, and a gradual reënforcement of
the successful one, these are unanimous, save in the very hardest, in
showing a process of sudden acquisition by a rapid, often apparently
instantaneous, abandonment of the unsuccessful movements and a selection
of the appropriate one which rivals in suddenness the selections made by
human beings in similar performances. It is natural to infer that the
monkeys who suddenly replace much general pulling and clawing by a single
definite pull at a hook or bar have an idea of the hook or bar and of the
movement they make. The rate of their progress is so different from that
of the cats and dogs that we cannot help imagining as the cause of it a
totally different mental function, namely, free ideas instead of vague
sense-impressions and impulses. But our interpretation of these results
should not be too hasty. We must first consider several other possible
explanations of the rapidity of learning by the monkeys before jumping to
the conclusion that the forces which bring about the sudden formation of
associations in human beings are present.

First of all it might be that the difference was due to the superiority
of the monkeys in clear detailed vision. It might be that in given
situations where associations were to be formed on the basis of smells,
the cats and dogs would show similar rapid learning. There might be,
that is, no general difference in type of mental functioning, but only
a special difference in the field in which the function worked. This
question can be answered by an investigation of the process of forming
associations in connection with smells by dogs and cats. Such an
investigation will, I hope, soon be carried on in the Columbia Laboratory
by Mr. Davis.[29]

Secondly, it might be that the superior mobility and more detailed
and definite movements of the monkeys’ hands might have caused the
difference. The slowness in the case of the dogs and cats might be at
least in part the result of difficulty in executing movements, not in
intending them. This difficulty in execution is a matter that cannot be
readily estimated, but the movements made by the cats and dogs would
not on their face value seem to be hard. They were mostly common to the
animals’ ordinary life. At the same time there were certain movements
(_e.g._ depressing the lever) which were much more quickly associated
with their respective situations by the cats than others were, and if
we could suppose that all the movements learned by the monkeys were
comparable to these few, it would detract from the necessity of seeking
some general mental difference as the explanation of the difference in
the results.

In the third place it may be said by some that no comparison of the
monkeys with dogs and cats is valid, since the former animals got out of
boxes while the latter got in. It may be supposed that the instinctive
response to confinement includes an agitation which precludes anything
save vague unregulated behavior. Professor Wesley Mills has made
such a suggestion in referring to the ‘Animal Intelligence’ in the
_Psychological Review_, May, 1899. In the July number of the same journal
I tried to show that there was no solid evidence of such a harmful
agitation. Nor can we be at all sure that agitation when present does not
rather quicken the wits of animals. It often seems to. However I should,
of course, allow that for purposes of comparison it would be better to
have the circumstances identical. And I should welcome any antagonist who
should, by making experiments with kittens after the fashion of these
with the monkeys, show that they did learn as suddenly as the latter.

Again we know that, whereas the times taken by a cat in a box to get
out are inversely proportional to the strength of the association,
inasmuch as they represent fairly the amount of its efforts, on the
other hand, the times taken by a monkey to get in represent the amounts
of his efforts _plus the amount of time in which he is not trying to
get in_. It may be said therefore that the time records of the monkeys
prove nothing,—that a record of four minutes may mean thirty seconds of
effort and three minutes thirty seconds of sleep,—that one minute may
really represent twice as much effort. As a matter of fact this objection
would occasionally hold against some single record. The earliest times
and the occasional long times amongst very short ones are likely to be
too long. The first fact makes the curves have too great a drop at the
start, making them seem cases of too sudden learning, but the second fact
makes the learning seem indefinite when it really is not. And in the long
run the times taken do represent fairly well the amount of effort. I
carefully recorded the amount of actual effort in a number of cases and
the story it tells concerning the mental processes involved is the same
as that told by the time-curves.

Still another explanation is this: The monkeys learn quickly, it is true,
but not quickly enough for us to suppose the presence of ideas, or the
formation of associations among them. For if there were such ideas, they
should in the complex acts do even better than they did. The explanation
then is a high degree of facility in the formation of associations of
just the same kind as we found in the chicks, dogs and cats.

Such an explanation we could hardly disapprove in any case. No one can
from objective evidence set up a standard of speed of learning below
which all shall be learning without ideas and above which all shall be
learning by ideas. We should not expect any hard and fast demarcation.

This whole matter of the rate of learning should be studied in the light
of other facts of behavior. My own judgment, if I had nothing but these
time-curves to rely on, would be that there was in them an appearance of
learning by ideas which, while possibly explicable by the finer vision
and freer movements of the monkey in connection with ordinary mammalian
mentality, made it worth while to look farther into their behavior. This
we may now do.

What leads the lay mind to attribute superior mental gifts to an animal
is not so much the rate of learning as the amount learned. The monkeys
obviously form more associations and associations in a greater variety
than do the other mammals. The improved rate assists, but another cause
of this greater number of associations is the general physical activity
of the monkeys, their constant movements of the hands, their instinctive
curiosity or tendency to fool with all sorts of objects, to enjoy having
sense-impressions, to form associations because of the resulting sound or
sight. These mental characteristics are of a high degree of importance
from the comparative point of view, but they cannot be used to prove that
the monkeys have free ideas, for a large number of associations may be
acquired after the purely animal fashion.

What is of more importance is the actual behavior of the animals in
connection with the boxes. First of all, as has been stated, all the
monkey’s movements are more definite, he seems not merely to pull, but
to pull at, not merely to poke, but to push at. He seems, even in his
general random play, to go here and there, pick up this, examine the
other, etc., more from having the idea strike him than from feeling like
doing it. He seems more like a man at the breakfast table than like a man
in a fight. Still this appearance may be quite specious, and I think it
is likely to lead us to read ideational life into his behavior if we are
not cautious. It may be simply general activity of the same sort as the
narrower activities of the cat or dog.

In the second place the monkeys often make special movements with a
directness which reminds one unavoidably of human actions guided by
ideas. For instance, No. 1 escaped from his cage one day and went
directly across the room to a table where lay a half of a banana which
was in a very inconspicuous place. It seemed as if he had observed the
banana and acted with the idea of its position fully in mind. Again, on
failing to pull a hook out, No. 1 immediately applied his teeth, though
he had before always pulled it out with his hand. So again with a plug.
It may be that there is a special inborn tendency to bite at objects
pulled unsuccessfully. If not, the act would seem to show the presence of
the idea ‘get thing out’ or ‘thing come out’ and associated with it the
impulse to use the teeth. We shall see later, however, that in certain
other circumstances where we should expect ideas to be present and result
in acts they do not.

The fact is that those features in the behavior of the monkeys in forming
associations between the sight of a box and the act needed to open it
which remind us of learning by ideas may also be possibly explained by
general activity and curiosity, the free use of the hand, and superior
quickness in forming associations of the animal sort. We must have
recourse to more crucial tests or at least seek evidence from a number of
different kinds of mental performances. The first of these will naturally
be their behavior toward these same mechanisms after a long time-interval.

THE PERMANENCE OF ASSOCIATIONS IN THE CASE OF MECHANISMS

My records are too few and in all but one case after too short an
interval to be decisive on the point of abrupt transition from failure
to success such as would characterize an animal in whose mind arose the
idea of a certain part of the mechanism as the thing to be attacked or of
a certain movement as the fit one. The animals are all under observation
in the Columbia Laboratory, however, and I trust that later satisfactory
tests may be made. No. 2 was not included in the tests because he was
either unwell or had become very shy of the boxes, entering them even
when the door was left open only after great delay. The time-curves for
the experiments performed will be found on page 186 among the others. The
figures beside each pair represent the number of days without practice.

The records show a decided superiority to those of the cats and dogs.
Although the number of trials in the original tests were in general fewer
in the case of the monkeys, the retention of the association is complete
in 6 cases out of 8 and is practically so in one case where the interval
was 8 months.

EXPERIMENTS ON THE DISCRIMINATION OF SIGNALS

My experiments on discrimination were of the following general type: I
got the animal into the habit of reacting to a certain signal (a sound,
movement, posture, visual presentation or what not) by some well-defined
act. In the cases to be described this act was to come down from his
customary positions about the top of the cage, to a place at the bottom.
I then would give him a bit of food. When this habit was wholly or
partly formed, I would begin to mix with that signal another signal
enough like it so that the animal would respond in the same manner. In
the cases where I gave this signal I would not feed him. I could then
determine whether the animal did discriminate or not, and his progress
toward perfect discrimination in case he did. If an animal responds
indiscriminately to both signals (that is, does not learn to disregard
the ‘no food’ signal) it is well to test him by using two somewhat
similar signals, after one of which you feed him at one place and after
the other of which you feed him at a different place.

If the animal profits by his training by acquiring ideas of the two
signals and associates with them ideas of ‘food’ and ‘no food,’ ‘go
down’ and ‘stay still,’ and uses these ideas to control his conduct, he
will, we have a right to expect, change suddenly from total failure to
differentiate the signals to total success. He will or won’t have the
ideas, and will behave accordingly. The same result could, of course, be
brought about by very rapid association of the new signal with the act
of keeping still, a very rapid inhibition of the act of going down in
response to it by virtue of the lack of any pleasure from doing so.

For convenience I shall call the signals after which food was given _yes_
signals and those after which food was not given _no_ signals. Signals
not described in the text are shown in Fig. 29, below. The progress of
the monkeys in discriminating is shown by Figs. 30 and 31, on pages 199
and 201. In Figs. 30 and 31 every millimeter along the horizontal or
base line represents 10 trials with the signal. The heights of the black
surface represent the percentages of _wrong_ responses, 10 mm. meaning
100 per cent of incorrect responses. Thus the first figure of the set,
Left hand, _a_, presents the following record: First 10 trials, all
wrong; of next 10, 7 wrong; of next 10, 6 wrong; of next 10, 7; of the
next, 9; of the next, 9; of the next, 4; of the next, none; of the next,
3; of the next, 2, and then 70 trials without an error.

[Illustration: FIG. 29.]

I will describe some of the experiments in detail and then discuss the
graphic presentation of them all.

EXPERIMENTS WITH NO. 1

Having developed in No. 1 the habit of coming down to the bottom of his
cage to get a bit of food when he saw me reach out and take such a bit
from my desk, I tested his ability to discriminate by beginning to use
now one hand, now the other, feeding him only when I used the left.
I also used different sets of words, namely, ‘I will give some food’
and ‘They shall not have any.’ It will be seen later that he probably
reacted only to the difference of the hands. The experiment is similar
to that described on pages 129 and 130 of Chapter II. At the beginning,
it should be remembered, No. 1 would come down whichever hand was used,
no matter what was said, except in the occasional cases where he was so
occupied with some other pursuit as to be evidently inattentive. He did
come to associate the act of going down with the one signal and the act
of staying still or continuing his ordinary movements with the other
signal. His progress in learning to do so is best seen in the curves of
his errors. To the ‘yes’ signal he responded correctly, except for the
occasional lapses which I just mentioned, from the start and throughout.
With the ‘no’ signal his errors were as shown in Fig. 30, _a_. The break
in the curve at 110 and 120 is probably not significant of an actual
retrograde as the trials concerned followed an eight days’ cessation of
the experiments.

I next tried No. 1 with an apparatus exposing sometimes a card with a
diamond-shaped piece of buff-colored paper on it and sometimes a card
with a similar black piece. The black piece was three fourths of an
inch farther behind the opening than the other. The light color was the
‘yes’ signal. The error curves for both signals are given, as No. 1 at
the beginning of the experiment did not go down always (Fig. 30, _b_ and
_b₁_).

I next tried No. 1 with the same apparatus but exposing cards with YES
and N in place of the buff and black diamonds. The record of the errors
is given in Fig. 30, _c_ and _c₁_. At the start he came down halfway very
often. This I arbitrarily scored as an error no matter which signal it
was in response to. It should not be supposed that these curves represent
two totally new associations. It seems likely that the monkey reacted to
the _position_ of the N card in the apparatus (the same as that of the
black diamond card) rather than to the shape of the letters. On putting
the black diamond in front he was much confused.

I next gave No. 1 the chance to form the habits of coming down when I
rapped my pencil against the table twice and of staying where he was when
I rapped with it once. He had 90 trials of each signal but failed to give
evidence of any different associations in the two cases.

Experiments of this sort were discontinued in the summer. In October I
tried No. 1 with the right and left hand experiment, he being in a new
room and cage, and I being seated in a different situation. He came down
at both signals and failed to make any ascertainable progress with the no
signal in 80 trials. (October 20-24.)

[Illustration: FIG. 30.]

I then tried him with the black and buff diamonds, the black being in
front (October 25-29). The reaction to the ‘yes’ signal was perfect from
the start. The progress with the ‘no’ signal is shown in Fig. 30, _d_.

I then tried him with an apparatus externally of different size, shape
and color from that so far used, showing as the ‘yes’ signal a brown
card and as the ‘no’ signal a white and gold card one half inch farther
back in the apparatus. The ‘yes’ signal was practically perfect from the
start. His progress with the ‘no’ signal is shown in Fig. 30, _e_.

I then tried a still different arrangement for exposure, to which,
however, he did not give uniform attention.

I then tried cards 1 and 101, 101 being in front and 1 in back. 1 was
the ‘yes’ signal. ‘Yes’ responses were perfect from the start. For ‘no’
responses see Fig. 30, _f_. I then put the ‘yes’ signal in front and the
‘no’ signal behind. ‘Yes’ responses perfect; for ‘no’ responses see Fig.
30, _f_, _a_.

From now on I arranged the exposures in such a way that there was no
difference between the ‘yes’ and ‘no’ signals in distance or surroundings.

The following list shows the dates, signals used, and the figures on
page 199 presenting the results. Where there is only one figure drawn,
it refers to progress with the ‘no’ signal, the ‘yes’ signal being
practically perfect from the start.

TABLE 10

==================+==============+=============+========
| ‘YES’ SIGNAL | ‘NO’ SIGNAL | FIGURE
------------------+--------------+-------------+--------
Nov. 13-15, 1900. | 2 | 102 | _g g₁_
Nov. 14-16, 1900. | 3 | 103 | _i i₁_
Nov. 16-19, 1900. | 4 | 104 | _h_
Nov. 19, 1900. | 5 | 105 | _j_
Nov. 20, 1900. | 6 | 106 | _k_
Nov. 21, 1900. | 7 | 107 | _l_
Nov. 23(?), 1900. | 8 | 108 | _m_
Nov. 27-29, 1900. | 9 | 109 | _n_
Nov. 30, 1900. | 10 | 110 | _o_
==================+==============+=============+========

Fig. 29 gives facsimiles of the different signals reduced to one sixth
their actual size. The drawing of 101 is not accurate, the outer ring
being too thick.

EXPERIMENTS WITH NO. 2

[Illustration: FIG. 31.]

I first secured the partial formation of the habit of coming down when
I took a bit of food in my hand. I then used the apparatus for exposing
cards, YES in front being the ‘yes’ signal and a circle at the back being
the ‘no’ signal. I gave No. 2 25 trials with the ‘yes’ signal and then
began a regular experiment similar to those described. After about 90
trials (November 9-12, 1900) there was no progress toward differentiation
of response, and it was evident from No. 2’s behavior that he was
reacting solely to the movements of my hand. So I abandoned the exposing
apparatus and used (November 11-13, 1900) as the ‘yes’ signal the act of
taking the food with my left hand from a pile on the front of the box and
for the ‘no’ signal the act of taking food with my right hand from a pile
4 inches behind that just mentioned. No. 2 did come to differentiate
these two signals. The record of his progress is given in Fig. 31 by _A_
and _A₁_.

I then made a second attempt with the exposing apparatus, using cards 2
and 102 (November 6, 14-21). No. 2 did react to my movements in pulling
the string but in over 100 trials made no progress in the direction of
a differential reaction to the ‘no’ signal. I then tried feeding him at
each signal, feeding him at the bottom of the cage as usual when I gave
the ‘yes’ signal and at the top when I gave the ‘no’ signal. After a
hundred trials with the ‘no’ signal there was no progress.

I then abandoned again the exposing apparatus and used as signals the
ordinary act of taking food with my left hand (yes) and the act of moving
my left arm from my right side round diagonally (swinging it on my elbow
as a center) and holding the hand, after taking the food, _palm up_ (no)
(November 26, 27, 1900). No. 2 did come to differentiate these signals.
His progress is given in the diagram in Fig. 31 entitled ‘Palm up’ (_B_).

I next used (November 27, 1900) as the ‘yes’ signal the same act as
before and for the ‘no’ signal the act of holding the food just in front
of the box about four inches below the edge. No. 2’s progress is shown in
Fig. 31 in the diagram entitled ‘low front’ (_C_ and _C₁_).

I next used (November 27-30) the same movement for both ‘yes’ and ‘no’
signals save that as the ‘yes’ signal I took the food from a brown
pasteboard box 3 by 3 by 0.5, and as the ‘no’ signal I took it from a
white crockery cover two inches in diameter and three eighths of an
inch high which was beside the box but three inches nearer me. No. 2’s
progress is shown in Fig. 31 in the diagram entitled ‘Box near’ (_D_).

I next used for the ‘yes’ signal the familiar act and for the ‘no’
signal the act of holding the food six inches above the box instead of
a quarter or a half an inch. The progress is shown in Fig. 31, _E_ and
_E₁_. I then tried taking the food from a saucer off the front of the
box for the ‘yes’ signal and from a small box at the back for the ‘no’
signal. ‘Yes’ was perfect from the start (10 trials given). ‘No’ was
right once, then wrong once, then right for the remaining eight.

EXPERIMENTS WITH NO. 3

No. 3 was kept in a cage not half so big as those of 1 and 2. Perhaps
because of the hindrance this fact offered to forming the habit of
reacting in some definite way to ‘yes’ signals, perhaps because of
the fact that I did not try hand movements as signals, there was no
successful discrimination by No. 3 of the yellow from the black diamond
or of a card with YES from a card with a circle on it. I tried climbing
up to a particular spot as the response to the ‘yes’ signal and staying
still as the response to the ‘no’ signal. I also tried instead of the
latter a different act, in which case the animal was fed after both
signals but in different places. In the latter case No. 3 made some
progress, but for practical reasons I postponed experiments with him.
Circumstances have made it necessary to postpone such experiments
indefinitely.

PERMANENCE OF THE ABILITY TO DISCRIMINATE

No. 1 and No. 2 were tried again after intervals of 33 to 48 days. The
results of these trials are shown in Fig. 32. Here every millimeter
along the base line represents _one_ trial with the ‘no’ signal (the
‘yes’ signals were practically perfect), and failure is represented by a
column 10 mm. high while success is represented by the absence of any
column. Thus the first record reads, “No. 1 with signal 104 after 40
days made 5 failures, then 2 successes, then 1 failure, then 1 success,
then 3 failures, then 1 success, then 1 failure, then 3 successes, then
1 failure, then 10 successes.” The third record (106; 40 days) reads,
“perfect success in ten trials.”

[Illustration: FIG. 32.]

DISCUSSION OF RESULTS

The results of all these discrimination experiments emphasize the
rapidity of formation of associations amongst the monkeys, which appeared
in their behavior toward the mechanisms. The suddenness of the change in
many cases is immediately suggestive of human performances. If all the
records were like c, f, h, i, j, k, l, m, B, E, and memory trials 103,
A, B, and C, one would have to credit the animals with either marvelous
rapidity in forming associations of the purely animal sort or concede
that from all the objective evidence at hand they were shown to learn as
human beings would. One would have to suppose that they had clear ideas
of the signals and clean-cut associations with those ideas. The other
records check such a conclusion.

In studying the figures we should remember that occasional mistakes, say
1 in 10 trials, are probably not significant of incomplete learning but
of inattention or of precipitate action before the shutter had fairly
exposed the card. We must not expect that a monkey who totally fails to
discriminate will _always_ respond wrongly to the ‘no’ signal, or that
a monkey who has come to discriminate perfectly will _always_ respond
rightly. A sudden drop from an average high level of error to an average
low level will signify sudden learning. Where the failure was on the
first trial of a series a few hours or a day removed from the last
series, I have generally represented the fact not by a column 1 mm. high
and 1 mm. broad, but by a single 10 mm. perpendicular. See i and A. Such
cases represent probably the failure of the animal to keep his learning
permanent rather than any general inability to discriminate.

K was to some extent a memory trial of d (after over half a year).

The experiment with 10 and 110 is noteworthy. Although, as can be seen
from the figures, the difference is obvious to one looking at the white
part of the figure, it is not so to one looking at the black part. No.
1 failed to improve appreciably in fifty trials, probably because his
previous experience had gotten him into the habit of attending to the
black lines.

Before arguing from the suddenness of the change from failure to success
we have to consider one possibility that I have not mentioned, and in
fact for the sake of clearness in presentation have rather concealed. It
is that the sudden change in the records, which report only whether the
animal did or did not go down, may represent a more gradual change in
the animal’s mind, a gradual weakening of the impulse to go down which
makes him feel less and less inclined to go down, though still doing so,
until this weakening reaches a sort of saturation point and stops the
action. There were in their behavior some phenomena which might witness
to such a process, but their interpretation is so dependent on the
subjective attitude and prepossessions of the observer that I prefer not
to draw any conclusions from them. On the other hand, records c, g, n, A
and D seem to show that gradual changes can be paralleled by changes in
the percentage of failures.

In the statement of conclusions I shall represent what would be the
effect on our theory of the matter in both cases, (1) taking the records
to be fairly perfect parallels of the process, and (2) taking them to be
the records of the summation points of a process not shown with surety in
any measurable objective facts. But I shall leave to future workers the
task of determining which case is the true one.

If we judge by the objective records themselves, we may still choose
between two views. (1) We may say that the monkeys did come to have
ideas of the acts of going down to the bottom of the cage and of staying
still, and that their learning represented the association of the
sense-impressions of the two signals, one with each of these ideas, or
possibly their association with two other ideas (of being fed and of
not being fed), and through them with the acts. Or (2) we may say that
the monkeys had no such ideas, but merely by the common animal sort of
association came to react in the profitable way to each signal.

If we take the first view, we must explain the failure of the animals
to change suddenly in some of the experiments, must explain why, for
instance, No. 1 in g should, after he had responded correctly to the
‘no’ signal for 27 trials out of 30, fail in one trial out of four for
a hundred or more trials. If the 27 successes were due to ideas, why
was there regression? If the animal came to respond by staying still on
seeing the K (card 104), because that sight was associated with the idea
of no food or the idea of staying still, why did he, in his memory trial,
act sometimes rightly, sometimes wrongly, for eleven trials after his
acting rightly twice. If he stayed still because the idea was aroused,
why did he not stay still as soon as he had a few trials to remind him of
the idea? It is easy, one may say, to see why, with a capacity to select
movements and associate them with sense-presentations very quickly, in
cases where habit provides only two movements for selection and where the
sense-presentation is very clear and simple, an animal should practically
at once be confirmed in the one act on an occasion when he does it with
the sense-impression in the focus of attention. It is easy, therefore, to
explain the sudden change in i, l, m, B, C and E. But our critic may add,
“It is very hard to suppose that an animal that learned by connecting
the sight of a card with the idea ‘stay still’ or the idea ‘no food,’
should be so long in making the connection as was the case in some of
these experiments, should take 10, 20 or 40 trials to change from a high
percentage of wrong to a high percentage of right reactions.”

If we take the second view, we have to face the fact that many of the
records are nothing like the single one we have for comparison, that of
the kitten shown in Fig. 30, and that the appeal to a capacity to form
animal associations very quickly seems like a far-fetched refuge from the
other view rather than a natural interpretation. If we take the records
to be summation points in a more gradual process, this difficulty is
relieved.

If further investigation upheld the first view, we should still not have
a demonstration that the monkeys habitually did learn by getting percepts
and images associated with sense-impressions, by having free ideas of the
acts they performed; we should only have proved that they could under
certain circumstances.

The circumstances in these experiments on discrimination were such as to
form a most favorable case. The act of going down had been performed in
all sorts of different connections and was likely to gain representation
in ideational life; the experience ‘bit of banana’ had again been
attended to as a part of very many different associations and so would be
likely to develop into a definite idea.

These results then do not settle the choice between three theories: (1
_a_) that they were due to a general capacity for having ideas, (1 _b_)
that they were due to ideas acquired by specially favoring circumstances,
(2) that they were due to the common form of association, the association
of an impulse to an act with a sense-impression rather roughly felt.

It would be of the utmost interest to duplicate these experiments with
dogs, cats and other mammals and compare the records. Moreover, since
we shall find (1 _a_) barred out by other experiments, it will be of
great interest to test the monkeys with some other type of act than
discrimination to see if, by giving the animal experience of the act and
result involved in many different connections, we can get a rate of speed
in the formation of a new association comparable to the rates in some of
these cases.

Of course here, as in our previous section, the differences in the
sense-powers of the monkeys from those of the kitten which I have tested
with a similar experiment may have caused the difference in behavior.
Focalized vision lends itself to delicate associations. Perhaps if one
used the sense of smell, or if the dogs and cats could, preserving their
same mental faculties in general, add the capacity for focalized vision,
they would do as well as the monkeys.

EXPERIMENTS ON THE INFLUENCE OF TUITION

The general aim of these experiments was to ascertain whether the
monkeys’ actions were at all determined by the presence of free ideas
and if so, to what extent. The question is, “Are the associations which
experience leads them to form, associations between (1) the idea of an
object and (2) the idea of an act or result and (3) the impulses and act
itself, or are they merely associations between the sense-impression
of the object and the impulse and act?” Can a monkey learn and does he
commonly learn to do things, not by the mere selection of the act from
amongst the acts done by him, but by getting some idea and then himself
providing the act because it is associated in his mind with that idea. If
a monkey feels an impulse to get into a box, sees his arm push a bar and
sees a door fall open immediately thereafter and goes into the box enough
times, he has every chance to form the association between the impulse to
get into the box and the idea ‘arm push bar,’ provided he can have such
an idea. If his general behavior is due to having ideas connected with
and so causing his acts, he has had chance enough to form the association
between the idea ‘push at’ and the act of pushing. If then a monkey forms
an association leading to an act by being put through the act, we may
expect that he has free ideas. And if he has free ideas in general in
connection with his actions, we may expect him to so form associations.
So also if a monkey shows a general capability to learn from seeing
another monkey or a human being do a thing. A few isolated cases of
imitation, however, might witness not to any general mental quality, but
only to certain instincts or habits differing from others only in that
the situation calling forth the act was the same act performed by another.

If the monkeys do not learn in these ways, we must, until other evidence
appears, suppose them to be in general destitute of a life of free ideas,
must regard their somewhat ambiguous behavior in learning by their
own unaided efforts as of the same type as that of the dogs and cats,
differing only in the respects mentioned on pages 190 and 191.

The general method of experimentation was to give monkeys who had failed
of their own efforts to operate some simple mechanism, a chance to see
me do it or see another monkey do it or to see and feel themselves do
it, and then note any change in their behavior. The chief question is
whether they succeed after such tuition when they have failed before
it, but the presence of ideas would also be indicated if they attacked,
though without success, the vital point in the mechanism when they had
not done so before. On the other hand, mere success would not prove that
the tuition had influenced them, for if they made a different movement
or attacked a different spot, we could not attribute their behavior to
getting ideas of the necessary act.

The results of the experiments as a whole are on their face value a
trifle ambiguous, but they surely show that the monkeys in question had
no considerable stock of ideas of the objects they dealt with or of the
movements they made and were not in general capable of acquiring, from
seeing me or one of their comrades attack a certain part of a mechanism
and make a certain movement, any ideas that were at all efficacious in
guiding their conduct. They do not acquire or use ideas in anything that
approaches the way human adults do. Whether the monkeys may not have some
few ideas corresponding to habitual classes of objects and acts is a
different question. Such may be present and function as the excitants of
acts.

It is likely that this question could have been definitely solved if it
had been possible for me to work with a larger number of animals. With
enough subjects one could use the method mentioned on page 105 of Chapter
II, of giving the animals tuition in acts which they would eventually do
themselves without it, and then leaving them to their efforts, noting any
differences in the way they learned from that in which other subjects who
had no tuition learned the same acts. The chief of such differences to
note would be differences in the time of their first trial, in the slope
of the time-curve and in the number of useless acts.

It would also be possible to extend experiments of the type of the
(on chair) experiment, where a subject is given first a certain time
(calculated by the experimenter to be somewhat less than would be needed
for the animal to hit upon the act) and if he does fail is then given
certain tuition and then a second trial. The influence of the tuition is
estimated by the presence or absence of cases where after tuition the act
is done within the time.

There is nothing necessarily insoluble in the problem. Given ten or
twenty monkeys that can be handled without any difficulty and it could be
settled in a month.

With this general preface we may turn to the more special questions
connected with the experiments on imitation of human acts and of the acts
of other monkeys and on the formation of associations apart from the
selection of impulses.

IMITATION OF HUMAN BEINGS

It has been a common opinion that monkeys learned to do things from
seeing them done by human beings. We find anecdotes to that effect in
fairly reputable authors.

Of course, such anecdotes might be true and still not prove that the
animals learned to do things because they saw them done. The animal
may have been taught in other ways to respond to the particular sights
in question by the particular acts. Or it may have been in each case a
coincidence.

If a monkey did actually form an association between a given situation
and act by seeing some one respond to that situation by that act, it
would be evidence of considerable importance concerning his general
mental status, for it would go to show that he could and often did form
associations between sense-impressions and ideas and between ideas and
acts. Seeing some one turn a key in a lock might thus give him the
idea of turning or moving the key, and this idea might arouse the act.
However, the mere fact that a monkey does something which you have just
done in his presence need not demonstrate or even render a bit more
probable such a general mental condition. For he perhaps would have acted
in just the same manner if you had offered him no model. If you put
two toothpicks on a dish, take one and put it in your mouth, a monkey
will do the same, not because he profits by your example, but because
he instinctively puts nearly all small objects in his mouth. Because of
their general activity, their instinctive impulses to grab, drop, bite,
rub, carry, move about, turn over, etc., any novel object within their
reach, their constant movement and assumption of all sorts of postures,
the monkeys perform many acts like our own and simulate imitation to a
far greater extent than other mammals.

Even if a monkey which has failed of itself to do a certain thing does it
after you have shown him the act, there need be no reason to suppose that
he is learning by imitation, forming an association between the sight of
the object and the act towards it through an idea gained from watching
you. You may have caused his act simply by attracting his attention to
the object. Perhaps if you had pointed at it or held it passively in your
hand, you would have brought to pass just the same action on his part.
There are several cases among my records where an act which an animal
failed totally to do of himself was done after I had so attracted his
attention to the object concerned.

Throughout all the time that I had my monkeys under observation I never
noticed in their general behavior any act which seemed due to genuine
imitation of me or the other persons about. I also gave them special
opportunities to show such by means of a number of experiments of the
following type: where an animal failed by himself to get into some box or
operate some mechanism, I would operate it in his presence a number of
times and then give him a chance to profit by the tuition. His failure
might be due to (1) the absence of instinctive impulses to make the
movement in that situation, (2) to lack of precision in the movement, (3)
to lack of force, or (4) to failure to notice and attack some special
part of the mechanism. An instance of (1) was the failure to push away
from them a bar which held a door; an instance of (2) was the failure to
pull a wire loop off a nail; an instance of (2) or (3) was the failure to
pull up a bolt; an instance of (4) was the failure to pull up an inside
bar. Failures due to (3) occur rarely in the case of such mechanisms as
were used in my investigations.

The general method of experiment was to make sure that the animal would
not of itself perform a certain act in a certain situation, then to make
sure that his failure could not be remedied by attracting his attention
to the object, then to perform the act for him a number of times, letting
him get each time the food which resulted, and finally to see whether,
having failed before the tuition, he would succeed after it. This sounds
very simple, but such experiments are hard to carry out satisfactorily.
If you try the animal enough times by himself to make quite sure that
he will not of himself hit upon the act, you are likely to form in him
the habit of meeting the particular situation in question with total
disregard. His efforts having failed so often may be so inhibited that
you could hardly expect any tuition to give them new life. The matter is
worse if you add further enough trials to assure you that your attracting
his attention to it has been unavailing. On the other hand, if you take
failure in five or ten minutes to mean inability, and from subsequent
success after imitation argue that imitation was efficient, you have to
face the numerous cases where animals which have failed in ten minutes
have succeeded in later unaided trials. With dogs and cats this does
not much matter, because they are steady performers, and their conduct
in one short trial tells you what to expect with some probability. But
the monkeys are much more variable and are so frequently distracted that
one feels much less confidence in his predictions. Moreover, you cannot
be at all sure of having attracted a monkey’s attention to an object
unless he does touch it. Suppose, for example, a monkey has failed to
even touch a bar though you have put a bit of food on it repeatedly. It
is quite possible that he may look at and take the food and not notice
the bar, and the fact that after such tuition he still fails to push or
pull the bar may mean simply that it has not caught his notice. I have,
therefore, preferred in most cases to give the animals only a brief
period of trial to test their ability by their own unaided efforts and
to omit the attempts to test the efficacy of attracting their attention
to the vital point in the mechanism. This makes the results appear less
elegant and definitive but really increases their value for purposes of
interpretation.

The thoughtful reader will not expect from my experiments any perfectly
rigorous demonstration of either the presence or the absence of imitation
of human acts as a means of learning. The general trend of the evidence,
it seems to me, is decidedly towards justifying the hypothesis that the
monkeys did not learn acts from seeing me do them.

I will first describe a sample experiment and then present a summary of
all those made.

On January 12th I put box Epsilon (push down) in No. 3’s cage, the door
of the box being open. I put a bit of food in the box. No. 3 reached
in and took it. This was repeated three times. I then put in a bit of
food and closed the door. No. 3 pulled and bit the box, turned it over,
fingered and bit at the hole where the lever was, but did not succeed
in getting the door open. After ten minutes I took the box out. Later I
took No. 3 out and let him sit on my knees (I sitting on the floor with
the box in front of us). I would then put my hand out toward the box and
when he was looking at it would insert my finger and depress the lever
with as evident a movement as I could. The door, of course, opened, and
No. 3 put his arm in and took the bit of food. I then put in another,
closed the door and depressed the lever as before. No. 3 watched my hand
pretty constantly, as all his experiences with me had made such watching
profitable. After ten such trials he was put back in the cage and the
box put in with a large piece of food in it and its door closed. No. 3
failed in five minutes and the box was taken out. He was shown fifteen
times more and then left to try himself. I tried him for a couple of
minutes under just the same circumstances as existed during the tuition,
_i.e._ he on the floor by me, the box in front. In this trial and in a
five-minute trial inside his cage he failed to open the door or to differ
in any essential respect from his behavior before tuition.

No. 1 saw me do 9 different acts and No. 3, 7, which they had failed
of themselves to do.[30] After from 1 to 40 chances to imitate me they
still failed to operate at all 11 of these mechanisms. In the case of
3 out of 5 that were worked the act was not the same as that taught.
No. 1, who saw me pull a nail out by taking the end of it and pulling
the nail away from the box, himself put his hand round the nail and
wriggled it out by pulling his hand back and forth. No. 3, who saw me
pull a bolt up with my fingers, succeeded by jerking and yanking the door
until he shook the bolt up. He saw me pull a hook out of an eye, but he
succeeded by pulling at a bar to which it was attached. In the case of
one of the two remaining acts (No. 3 with _nail chute_) the act was done
once and never again, though ample opportunity was given and tuition
continued. It could, therefore, hardly have been due to an idea instilled
by the tuition. The remaining case, No. 1, with loop, must, I think,
be attributed to accident, especially since No. 3 failed to profit by
precisely the same sort of tuition with precisely the same act.

Nor is there any evidence to show that although tuition failed to cause
successes where unaided effort failed, it yet caused attempts which would
not otherwise have occurred. Out of fifteen cases where such might have
appeared, there were only three where it is possible to claim that they
did. No one of these three is a sure case. With RR (wood plug) No. 1 did
seem to pull the plug more definitely after seeing me than before. With
QQ (c) (nail chute) and MM (bolt at top) he may possibly have done so.

In 5 cases I tried the influence of seeing me make the movement on
animals who had done the act of themselves, the aim being to see whether
there would be a marked shortening of the time, a change in their way of
operating the mechanism or an attempt at such change. I will give the
essential facts from the general table on pages 226-229.

(_a_) No. 1 had succeeded in pulling in the box by the upper string in
OOO (upper string box) in 2.20 and then failed in 3.00. I showed him 4
times. He failed in 10. I showed him 4 more times. He failed in 10. I
showed him 4 more times. He succeeded in .20. No change in manner of act
or objects attacked, though my manner was different from his.

(_b_) No. 1 had succeeded in QQ (a) (chute bar) in 8.00. I showed him 20
times. He failed in 10. I showed him 10 more times. He succeeded in 2.00.
I showed him 10 more times. He succeeded in 50 seconds. No change in his
manner of performance or in the object attacked, though my manner was
different from his.

(_c_) No. 1 had succeeded in 3.00, .25, .07, .25, .20, .06 and .09 with
QQ (b) (chute bar double) and then failed in 5.00. I showed him 10 times.
He then failed in 5 twice, succeeded in 3.00, and failed in 5 again. No
change in manner of performance or in the object attacked, though my
manner was different from his.

(_d_) No. 3 had the following record in box Delta:—

2.00 (pushed with head)
3.20 (pushed with head)
30 F
10 F
10 F
2.10 (pulled wire and door).

I showed him 20 times by pushing the bar to the right with my finger. He
succeeded in 8.00 and 8.00 by pulling the wire and the door. No change in
object attacked.

(_e_) No. 2 had failed twice in 5 with chute QQ (ff) (chute string wire)
and succeeded once in 2.00 by a strong pull on the wire itself, not the
loop. I showed him 5 times, pulling the loop off the nail. He then failed
in 5. There was no change in the objects attacked.

These records show no signs of any influence of the tuition that are
not more probably signs of something else. We cannot attribute the
rapid decrease in time taken in (_b_) to the tuition until we know the
time-curve for the same process without tuition.

The systematic experiments designed to detect the presence of ability to
learn from human beings are thus practically unanimous against it. So,
too, was the general behavior of the monkeys, though I do not consider
the failure of the animals to imitate common human acts as of much
importance save as a rebuke to the story-tellers and casual observers.
The following facts are samples: The door of No. 1’s cage was closed by
an iron hoop with a slit in it through which a staple passed, the door
being held by a stick of wood thrust through the staple. No. 1 saw me
open the door of his and other cages by taking out sticks hundreds of
times, but though he escaped from his cage a dozen times in other ways,
he never took the stick out and to my knowledge never tried to. I myself
and visitors smoked a good deal in the monkeys’ presence, but a cigar or
cigarette given to them was always treated like anything else.

IMITATION OF OTHER MONKEYS

It would theoretically seem far more likely that the monkeys should
learn from watching each other than from watching human beings, and
experimental determinations of such ability are more important than those
described in the last section as contributions both to genetic psychology
and to natural history. I regret that the work I have been able to do in
the study of this phase of the mental life of the monkeys has been very
limited and in many ways unsatisfactory.

We should expect to find the tendency to imitation more obvious in the
case of young and parents than elsewhere. I have had no chance to observe
such cases. We should expect closely associated animals, such as members
of a common troop or animals on friendly terms, to manifest it more
than others. Unfortunately, two of my monkeys, by the time I was ready
to make definite experiments, were on terms of war. The other had then
become so shy that I could not confidently infer inability to do a thing
from actual failure to do it. He showed no evidence of learning from his
mates. I have, therefore, little evidence of a quantitative objective
nature to present and shall have in the end to ask the reader to take
some opinions without verifiable proofs.

My reliable experiments, five in number, were of the following nature. A
monkey who had failed of himself (and often also after a chance to learn
from me or from being put through the act) would be put where he could
see another do the act and get a reward (food) for it. He would then be
given a chance to do it himself, and note would be taken of his success
or failure, and of whether his act was the same as that of his model in
case he succeeded, and of whether he tried that act more than before the
tuition in case he tried it and failed. The results are given in Table 11.

In the fourth experiment No. 1 showed further that the tuition did not
cause his successes in that after some successes further tuition did not
improve him.

There is clearly no evidence here of any imitation of No. 1 by No. 3.
There was also apparently nothing like purposive watching on the part
of No. 3. He seemed often to see No. 1 open the box or work the chute
mechanism, but without special interest.

This lack of any special curiosity about the doings of their own species
characterized the general behavior of all three of my monkeys and in
itself lessens the probability that they learn much from one another. Nor
did there appear, in the course of the three months and more the animals
were together, any signs of imitation. There were indeed certain notable
instances of the lack of it in circumstances which one would suppose
would be favorable cases for it.

For instance: No. 2 was very timid. No. 1 was perfectly tame from the
first day No. 2 was with me, and No. 3 became tame shortly after. No.
2 saw Nos. 1 and 3 come to me, be played with, fed and put through
experiments, yet he never did the same nor did he abate a jot or tittle
from his timidity save in so far as I sedulously rewarded any chance
advances of his. Conversely No. 1 and No. 3 seemed uninfluenced by the
fear and shyness of No. 2. No. 2’s cage was between No. 1’s and No. 3’s,
and they were for three weeks incessantly making hostile demonstrations
toward each other, jumping, chattering, scowling, etc. No. 2 never did
anything of the sort. Again, seeing No. 3 eat meat did not lead No. 1 to
take it; nor did seeing No. 1 retreat in fright from a bit of absorbent
cotton lead No. 3 to avoid it.

TABLE 11

Table headings:
Column A: SUBJECT, DATE, ACT
Column B: TIME TRIED ALONE, WITH RESULT
Column C: NO. OF TIMES IMITATEE DID
Column D: RESULT AFTER CHANCE FOR IMITATION
Column E: SIMILARITY OR DISSIMILARITY OF ACT
Column F: SIMILAR ACT ATTEMPTED, THOUGH UNSUCCESSFULLY IN CASES WHERE
IT HAD NOT BEEN BEFORE TRAINING
Column G: GENERAL JUDGMENT AS TO INFLUENCE OF TRAINING

======================+========+====+======+=============+=====+=======
A | B | C | D | E | F | G
----------------------+--------+----+------+-------------+-----+-------
No. 3. Dec. 17, 1900. | 50 F | 43 | 55 F | | No. | None.
VV (wire loop) | | | | | |
No. 3. Jan. 15, 1901. | 91 F | 75 | 35 F | | No. | None.
QQ (c) (nail chute) | 1.30 | | | | |
No. 3. Jan. 21, 1901. | 63 F | 43 | 5 F | Dissimilar. | No. | None.
Gamma (wind) | | | 9.00 | | |
| | | 6.00 | | |
No. 3. Jan. 21, 1901. | 20 F | 30 | 1.30 | Dissimilar. | No. | None.
QQ (ff) (string | 2.00 | | .40 | | |
chute with wire) | | | .35 | | |
| | | 5 F | | |
No. 3. Jan. 23, 1901. | 1.15 F | 40 | 10 F | | No. | None.
QQ (chute) | | | | | |
======================+========+====+======+=============+=====+=======

Nothing in my experience with these animals, then, favors the hypothesis
that they have any general ability to learn to do things from seeing
others do them. The question is still an open one, however, and a much
more extensive study of it should be made, especially of the possible
influence of imitation in the case of acts already familiar either as
wholes or in their elements.

LEARNING APART FROM MOTOR IMPULSES

The reader of my monograph, ‘Animal Intelligence,’ will recall that the
experiments there reported seemed to show that the chicks, cats and
dogs had only slight and sporadic, if any, ability to form associations
except such as contained some actual motor impulse. They failed to form
such associations between the sense-impressions and ideas of movements
as would lead them to make the movements without having themselves
previously in those situations given the motor impulses to the movements.
They could not, for instance, learn to do a thing from having been put
through it by me.

The monkeys Nos. 1 and 3 were tested in a similar way with a number of
different acts. The general conclusion from the experiments, the details
of which will be given presently, is that the monkeys are not proved to
have the power of forming associations of ideas to any greater extent
than the other mammals, that they do not demonstrably learn to do things
from seeing or feeling themselves make the movement. An adult human
being whose hand was taken and made to push in a bar or pull back a bolt
would thereby learn to do it for himself. Cats and dogs would not, and
the monkeys are not proved to do so. On the other hand, it is impossible
for me to say, as of the dogs and cats, that the monkeys are proved not
to do so. In a few cases the animals did perform acts after having been
put through them which they had failed to perform when left to their own
trial and success method. In the majority of cases they did not. And
in some of these latter cases failure seemed so improbable in case the
animal really had the power of getting an idea of the act and proceeding
from idea to execution, that one is inevitably led to some explanation
for the few successes other than the presence of ‘ideas.’

The general manner of making these experiments was like that in the case
of the cats and dogs, save that the monkey’s paw was used to open the
box from the outside instead of from the inside, and that the monkeys
were also put through the acts necessary to operate some of the chute
mechanisms. Tests parallel to that of comparing the behavior of kittens
who had themselves gone into boxes with those who were dropped in by me
were made in the following manner. I would carry a monkey from his cage
and put him in some conspicuous place (_e.g._ on the top of a chair)
and then give him a bit of food. This I would repeat a number of times.
Then I would turn him loose in the room to see whether he had acquired
an idea of being on the chair which would lead him to himself go to the
chair. I would, in order to tell whether his act, in case he did so, was
the result of random activities or was really due to his tuition, leave
him alone for 5 or 10 minutes before the tuition. If he got on the chair
afterwards when he had not before, or got on it much sooner, it would
tend to show that the idea of getting food on that chair was present and
effective. We may call these last the ‘on chair’ type of experiments.

A sample experiment with a box is the following:—

On January 4, 1901, box Delta (push back) was put in No. 1’s cage. He
failed in 5, though he was active in trying to get in for about 4 minutes
of the time and pulled and pushed the bar a great deal, though up and
down and out instead of back. In his aimless pushings and pullings he
nearly succeeded. He failed in 5 in a second trial also. I then opened
the door of the cage, sat down beside it, held out my hand, and when he
came to me took his right paw and with it (he being held in front of the
box) pushed the bar back (and pulled the door open in those cases when it
did not fall open of itself). He reached in and took the food and went
back to the top of his cage and ate it. (No. 1 generally did this, while
No. 3 generally stayed by me.) I then tried him alone; result 10 F; no
activity at all. On January 5th I put the box in; result 10 F. He was
fairly active. He pulled at the bar but mostly from a position on the top
of the box and with his left hand; no attempts like the one I had tried
to teach him. Being left alone he failed in 5. Being tried again with
the door of the cage open and me sitting as I had done while putting him
through the act, he succeeded in 7.00 by pushing the bar with his head
in the course of efforts to poke his head in at the door. I then put him
through the act 10 times and left him to himself. He failed in 5.00; no
activity. I then sat down by the cage as when teaching him. He failed in
5; little activity. Later in the day I put him through the act 10 times
and then left him to himself. He failed in 5; little activity. I sat
down as before. He failed in five; little activity. On January 6th I put
him through the act 10 times and then left him. He failed in 10. This
was repeated later in the day with the same result. Record:—By himself,
10 F. Put through 80 times. F 65 (a) [the (a) refers to a note of his
unrepeated chance success with his head]. No similar act unsuccessfully
attempted. Influence of tuition, none.

With the chute mechanisms the record would be of the same nature. With
them I put the animal through generally by taking his paw, held out
through the wire netting of the cage, and making the movement with it.
In one experiment (No. 3 with QQ chute) the first 58 trials were made by
taking the monkey outside the cage and holding him instead of having him
put his paw through the netting for me to take.

Many of the experiments were with mechanisms which had previously
been used in experiments concerning the ability to learn from seeing
me operate them. And the following Table (12) includes the results of
experiments of both sorts. The results of experiments of the ‘on chair’
type are in Table 13. In cases where the same apparatus was used for both
purposes, the sort of training which was given first is that where an A
is placed.

In the first four experiments with No. 1 there was some struggling and
agitation on his part while being held and put through the act. After
that there was none in his case except occasional playfulness, and there
was never any with No. 3 after the first third of the first experiment.
The monkeys soon formed the habit of keeping still, because it was only
when still that I put them through the act and that food resulted. After
you once get them so that they can be held and their arms taken without
their clinging to you, they quickly learn to adapt themselves to the
experiments.

With No. 1, out of 8 cases where he had of himself failed (in five of the
cases he had also failed after being shown by me), he succeeded after
being put through (13, 21, 51, 10, 7, 80, and 10 times) in two cases (QQ
(chute) and RR (wood plug). The act was unlike the one taught him in the
former case.

TABLE 12

Table headings:
Column A: SUBJECT. DATE. ACT
Column B: TIMES TRIED ALONE, WITH RESULT
Column C: NUMBER OF TIMES ATTENTION ATTRACTED
Column D: RESULT
Column E: NUMBER OF TIMES SHOWN BY ME
Column F: RESULT IN TRIALS AFTER BEING SHOWN BY ME
Column G: NUMBER OF TIMES PUT THROUGH THE ACT
Column H: RESULT IN TRIALS AFTER BEING PUT THROUGH THE ACT
Column I: COMPARISON OF ACT USED WITH ACT TAUGHT
Column J: SIMILAR ACT ATTEMPTED THOUGH UNSUCCESSFULLY
Column K: ACT DONE ONCE OR MORE, BUT NOT REPEATED IN SPITE OF
REPEATED TUITION

========================+==========+====+========+========+========+
A | B | C | D | E | F |
------------------------+----------+----+--------+--------+--------+
No. 1, Jan. 7, 1900, | 10 F | | | | |
PP (string across) | 10 F | | | | |
| | | | | |
No. 1, Jan. 17, 1900, | 15 F | | | 21 A |150 F |
MM (bolt at top) | | | | | 10 F |
| | | | | |
No. 1, Feb. 24, 1900, | 2.20 | | | 4} | 10 F |
OOO (upper string) | 3 F | | | 4} 12 | .20 |
| | | | 4} | |
| | | | 4 | .22 |
| | | | | |
No. 1, Mar. 24, 1900, | 120 F | | | 10 A | 60 F |
QQ (chute) | | | | | |
| | | | | |
No. 1, Apr. 5, 1900, | 10 F | 2 | 5 F | 1 A | 2 F |
RR (wood plug) | | | | 1 | 2 F |
| | | | 1 | 2 F |
| | | | 1 | 5 F |
| | | | | |
No. 1, Oct. 20, 1900, | 10 F | | | 4 | .22 |
VV (loop) | 10 F | | | | |
| 10 F | | | | |
| 10 F | | | | |
| | | | | |
No. 1, Nov. 19, 1900, | 10 F | | | 5 | 10 F |
Theta (new bolt) | | | | | |
| | | | | |
No. 1, Jan. 4, 1901, | 10 F | | | 15 | 10 F |
Delta (push back) | | | | | |
| | | | | |
No. 1, Jan. 6, 1901, | 8.00 | | | 40 | 10 F |
QQ (a) (single | | | | |2.00 |
wind chute) | | | | | .50 |
| | | | | |
No. 1, Jan. 7, 1901, | 5 F | | | | |
Zeta (side plug new) | | | | | |
| 1.10 | | | | |
| | | | | |
No. 1, Jan. 9, 1901, | 3.00 | | | 10 | 5 F |
QQ (b) (2½ | to .06 | | | | 5 F |
wind chute) | 5 F | | | |3.00 |
| | | | | 5 F |
| | | | | |
No. 1, Jan. 11, 1901, | 5 F | 5 | 5 F | 1[32] |2.20 |
QQ (c) (nail chute) | 5 F | | | | |
| | | | | |
No. 1, Jan. 12, 1901, | 5 F | | | 25 A | 10 F |
Epsilon (push down) | 10 F | | | | 10 F |
| | | | 15 | 10 F |
| | | | | |
No. 1, Jan. 16, 1901, | 5 F | 5 | 3.30 | | |
QQ (d) (pull chute) | 5 F | | .10 | | |
| | | | | |
No. 1, Jan. 17, 1901, | 5 F | 5 | 5 F | 15 A | 5 F |
QQ (f) (string chute) | | | | | 5 F |
| | | | | |
No. 1, Jan. 18, 1901, | 5 F | 3 | im. | | |
QQ (e) (hook chute) | | | | | |
| | | | | |
No. 3, Dec. 17, 1900, | 60 F | 3 | 60 F | 10 A | 5 F |
QQ (chute) | | | | 30 | 30 F |
| | | | | |
No. 3, Dec. 17, 1900, | 10 F | | | | |
VV (loop) | 20 F | | | | |
| | | | | |
No. 3, Jan. 4, 1901, | 10 F | | | 20 |8.00[34]|
Delta (push back) | 2.10 | | | |8.00[34]|
| (by | | | | |
| pulling | | | | |
| string) | | | | |
| | | | | |
No. 3, Jan. 4, 1901, | 10 F | | | 30 | 10 F |
Gamma (wind) | 10 F | | | | 10 F |
| | | | | |
No. 3, Jan. 8, 1901, | 10 F[36]| | | 25 | 6 F |
Theta (bolt at top) | | | | | |
| | | | | |
No. 3, Jan. 9, 1901, | 10 F | | | |3.00[37]|
QQ (a) (chute bar) | | | | | |
| | | | | |
| | | | | |
| | | | | |
No. 3, Jan. 9, 1901, | | | | | |
QQ (b) (2½ wind chute)| 10 F | | | 20 | 8 F |
| | | | | 8 F |
| | | | | |
No. 3, Jan. 11, 1901, | 5 F | 10 | 5 F | 25 A | 5 F |
QQ (c) (nail chute) | 5 F | |12 F[38]| | 5 F |
| | | | |1.30 |
| | | | | 5 F |
| | | | |10 F |
| | | | | |
No. 3, Jan. 15, 1901, | 10 F | | | 25 A | 5 F |
Epsilon (push down) | | | | | 5 F |
| | | | | |
| | | | | |
No. 3, Jan. 16, 1901, | | | | | |
QQ (e) (hook chute) | 5 F | 5 | 5 F | 5 A |2.00 |
| | | | |1.25 |
| | | | |1.20 |
| | | | | |
No. 3, Jan. 19, 1901, | 5 F | | 5 | 5 A | 5 F |
QQ (ff) (string chute | 5 F | | | | |
with wire) | 2.00[39] | | | | |
| | | | | |
| | | | | |
No. 3, Jan. 22, 1901, | 5 F | | | | |
WW (bar inside) |previously| | | | |
| some | | | | |
| 40.00 F | | | | |
========================+==========+====+========+========+========+

========================+======+========+===========+========+======
A | G | H | I | J | K
------------------------+------+--------+-----------+--------+------
No. 1, Jan. 7, 1900, | 13 | 10 F | | No. |
PP (string across) | | | | |
| | | | |
No. 1, Jan. 17, 1900, | 21 | 10 F | | (?) |
MM (bolt at top) | | | | |
| | | | |
No. 1, Feb. 24, 1900, | | | Partly | |
OOO (upper string) | | | similar. | No. |
| | | | |
| | | | |
| | | | |
No. 1, Mar. 24, 1900, | 10 | 30.00 |Dissimilar.| No. |
QQ (chute) | | | | |
| | | | |
No. 1, Apr. 5, 1900, | 7 | 2.20 | Similar. | Yes(?) |
RR (wood plug) | 2 | 2.00 | | |
| | | | |
| | | | |
| | | | |
No. 1, Oct. 20, 1900, | | | Similar. | |
VV (loop) | | | | |
| | | | |
| | | | |
| | | | |
No. 1, Nov. 19, 1900, | 51 A | 132 F | | No. |
Theta (new bolt) | | | | |
| | | | |
No. 1, Jan. 4, 1901, | 80 A |65 F[31]| | No. |
Delta (push back) | | | | |
| | | | |
No. 1, Jan. 6, 1901, | | |Dissimilar.| |
QQ (a) (single | | | | |
wind chute) | | | | |
| | | | |
No. 1, Jan. 7, 1901, | | | | |
Zeta (side plug new) | 20 | im. | ? | |
| | im. | | |
| | | | |
No. 1, Jan. 9, 1901, | | |Dissimilar.| No. |Yes.
QQ (b) (2½ | | | | |
wind chute) | | | | |
| | | | |
| | | | |
No. 1, Jan. 11, 1901, | | |Dissimilar.| |Yes.[33]
QQ (c) (nail chute) | | | | |
| | | | |
No. 1, Jan. 12, 1901, | 10 | 5 F | | No. |
Epsilon (push down) | 10 | 10 F | | |
| | | | |
| | | | |
No. 1, Jan. 16, 1901, | | | | |
QQ (d) (pull chute) | | | | |
| | | | |
No. 1, Jan. 17, 1901, | 10 | 5 F | | |
QQ (f) (string chute) | | | | |
| | | | |
No. 1, Jan. 18, 1901, | | | | |
QQ (e) (hook chute) | | | | |
| | | | |
No. 3, Dec. 17, 1900, |113 | 90 F | | (?) |
QQ (chute) | | | | |
| | | | |
No. 3, Dec. 17, 1900, | 23 | 20 F | | No. |
VV (loop) | | | | |
| | | | |
No. 3, Jan. 4, 1901, | 5 A |2.00[35]|Dissimilar.| No. |
Delta (push back) | 5 | 3.20 | | |
| 15 | 30 F | | |
| 5 | 10 F | | |
| | | | |
| | | | |
No. 3, Jan. 4, 1901, | 20 A | 5 F | | No. |
Gamma (wind) | | 8 F | | |
| | | | |
No. 3, Jan. 8, 1901, | | |Dissimilar.| |
Theta (bolt at top) | | | | |
| | | | |
No. 3, Jan. 9, 1901, | 10 | | | No |
QQ (a) (chute bar) | 10 | .40 | ? |complete|
| 10 | 1.00 | | circle.|
| 10 | 1.00 | | |
| | | | |
No. 3, Jan. 9, 1901, | | | | |
QQ (b) (2½ wind chute)| | 5 F |Dissimilar.| |Yes.
| | | | |
| | | | |
No. 3, Jan. 11, 1901, | 45 | 38 F | | No. |Yes.
QQ (c) (nail chute) | | | | |
| 10 | 10 F | | |
| | | | |
| | | | |
| | | | |
No. 3, Jan. 15, 1901, | 20 | 11.00 | | No. |Yes.
Epsilon (push down) | | 30 F | ? | |
| 15 | 10 F | | |
| | | | |
No. 3, Jan. 16, 1901, | | | | |
QQ (e) (hook chute) | 10 | .10 |Dissimilar.| No. |
| | .10 | | |
| | | | |
| | | | |
No. 3, Jan. 19, 1901, | 7 | 5 F | | |
QQ (ff) (string chute | 8 | 5 F | | |
with wire) | 12 | 3.00 |Dissimilar.| No. |
| | 5 F | | |
| | | | |
No. 3, Jan. 22, 1901, | 10 | 5 F | | |
WW (bar inside) | |6.00[40]| | |
| | | | |
| |7.00[40]|Dissimilar.| No. |
========================+======+========+===========+========+======

In only one case (bolt at top) out of eight was there possibly any
attempt at the act after he had been put through which had not been made
before. The ‘yes or?’ in the table with RR was a case occurring after the
imitation of me but before the putting No. 1 through.

Out of 6 cases where he had himself failed, No. 3 succeeded (after being
put through 113, 23, 20, 10, 10, 20 and 10 times) in 3 cases (chute bar,
push down and bar inside). The act was dissimilar in all three cases,
bearing absolutely no resemblance in one case. There was no unsuccessful
attempt at the act taught him in any of the cases. With the chute he
did finger the bar after tuition where he had not done so before, but
it was probably an accidental result of his holding his hand out toward
it for me to take as he had formed the habit of doing. In the case of
box Epsilon (push down), with which he succeeded by pushing his hand in
above the lever (an act which though unlike that taught him might be by
some considered to be due to an idea gained from the tuition), he failed
entirely after further tuition (15 times).

Like the dogs and cats, then, the monkeys seemed unable to learn to do
things from being put through them. We may now examine those which they
did do of themselves before tuition and ask whether they learned the more
rapidly thereby or modified their behavior in ways which might be due to
the tuition. There are too few cases and no chance for comparison on the
first point; on the second the records are unanimous in showing no change
in the method of operating the mechanisms due to the tuition.

As in Table 9, figures followed by F mean that in that length of time
the animal failed. Figures without an F denote the time taken by the
animal to operate the mechanism.

As a supplement to Table 12 I have made a summary of the cases where the
animals did succeed after tuition, that shows the nature of the act shown
them as compared with the act they made use of.

SUPPLEMENT TO TABLE 12

I have kept the results of the tests of the ‘on chair’ type separate from
the others because they may be tests of a different thing and surely are
subject to different conditions.

They were tests of the animals’ ability to form the habit of going to a
certain place by reason of having been _carried_ there and securing food
thereby. I would leave the animal loose in the room, and if he failed
in 5 or 10 minutes to go to the place of his own accord, would put him
back in his cage; if he did go of his own accord, I would note the time.
Then I would take him, carry him to the place, and feed him. After doing
this 10 times I would turn him loose again and see whether the idea of
being fed in such and such a place was present and active in making him
go to the place. In such tests we are absolutely sure that the animal can
without any difficulty perform the necessary movements and would in case
the proper stimulus to set them off appeared, if, for instance, a bit of
food on one of the places to which he was to go caught his eye. In so far
forth the tests were favorable cases for learning. On the other hand, the
situation associated with getting food may have been in these cases not
the mere ‘being on box’ but the whole previous experience ‘being carried
while clinging and being put or let jump on a box.’ In this respect the
tests may have been less favorable than the acts where getting food was
always the direct sequent of the act of going into the box.

The experiments were:—

A. Carrying the animal and putting him on a chair.

B. Carrying the animal and putting him on a pile of boxes.

C. Carrying the animal and putting him on the top of a sewing machine.

D. Carrying the animal and putting him on the middle of a board 6 feet
long, stretched horizontally across the room, 3 feet from the floor.

E. Carrying the animal and putting him on the side of the cage, head down.

The results are given in Table 13.

The size of the room in which I worked and other practical difficulties
prevented me from extending these experiments. As they stand, no stable
judgments can be inferred from them. It should be noted that in the
successful cases there were no other signs of the presence of the idea
‘food when there’ than the mere going to a certain place. The animal did
not wait at the place more than a second or two, did not look at me or
show any signs of expecting anything.

TABLE 13

================+==========+==============+===============+===========
EXPERIMENT | |RESULTS BEFORE|NUMBER OF TIMES| RESULTS
AND DATE | ANIMAL | TRAINING | PUT THROUGH | AFTER
| | | | TRAINING
----------------+----------+--------------+---------------+-----------
A. Jan. 22, 1901| No. 1. | 5 F | 10 | 1.00
| | | | 3.00
Jan. 22, 1901| No. 1. | 5 F | 10 | im.
| | | | 3.30
Jan. 23, 1901| No. 3. | 5 F | 10 | 3.30
| | 5 F | |
B. Jan. 26, 1901| No. 1. | 10 F | 10 and 5 | 10 F 5 F
| No. 3. | 5 F | 10 | 5 F
| | | 10 | 5 F
C. Jan. 27, 1901| No. 1. | 5 F | 10 | 3.00
D. Jan. 27, 1901| No. 1. | 3.20 | 10 | 5 F
E. Jan. 26, 1901| No. 3. | 5 F | 5 | 5 F
================+==========+==============+===============+===========

Although, as I noted in the early part of this monograph, there were
occasionally phenomena in the general behavior of the monkeys which of
themselves impressed one as being suggestive of an ideational life,
the general run of their learning apart from the specific experiments
described was certainly confined to the association of impulses of their
own with certain situations. The following examples will suffice:—

In getting them so that they would let themselves be handled it was of
almost no service to _take_ them and feed them while holding them or
otherwise make that state pleasant for them. By far the best way is to
wait patiently till they do come near, then feed them; wait patiently
till they do take hold of your arm, then feed them. If you do take them
and hold them partly by force, you must feed them only when they are
comparatively still. In short, in taming them one comes unconsciously
to adopt the method of rewarding certain of their impulses rather than
certain _conditions_ which might be associated in their minds with ideas,
had they such.

After No. 1 and No. 3 had both reached a point where both could hardly
be gotten to leave me and go back into their cages or down to the floor
of the room, where they evidently enjoyed being held by me, they still
did not climb upon me. The idea of clinging to me was either absent or
impotent to cause them to act. What they did do was, in the case of
No. 1, to jump about, pawing around in the air, until I caught an arm
or leg, to which stimulus he had by dint of the typical sort of animal
association learned to react by jumping to my arm and clinging there; in
the case of No. 3, to stand still until I held my arm right in front of
him (if he were in his cage) or to come and stand on his hind legs in
front of me (if he were out on the floor). In both cases No. 3’s act was
one which had been learned by my rewarding his impulses. I often tried,
at this period of their intimacy with me, this instructive experiment.
The monkey would be clinging to me so that I could hardly tear him away.
I would do so, and he would, if dropped loose from me, make no efforts to
get back.

I have already mentioned my failure to get the animals to put out their
right hands through the netting after they had long done so with their
left hands. With No. 3 I tried putting my fingers through and poking the
arm out and then making the movement with it. He profited little if any
by this tuition. Had I somehow induced him to do it himself, a few trials
would have been sufficient to get the habit well under way.

Monkey No. 1 apparently enjoyed scratching himself. Among the stimuli
which served to set off this act of scratching was the irritation from
tobacco smoke. If any one would blow smoke in No. 1’s face, he would
blink his eyes and scratch himself, principally in the back. After a
time he got in the habit of coming to the front of his cage when any one
was smoking and making such movements and sounds as in his experience
had attracted attention and caused the smoker to blow in his face. He
was often given a lighted cigar or cigarette to test him for imitation.
He formed the habit of rubbing it on his back. After doing so he would
scratch himself with great vigor and zest. He came to do this always
when the proper object was given him. I have recounted all this to show
that the monkey enjoyed scratching himself. _Yet he apparently never
scratched himself except in response to some sensory stimulus._ He was
apparently incapable of thinking ‘scratch’ and so doing. Yet the act was
quite capable of association with circumstances with which as a matter
of hereditary organization it had no connection. For by taking a certain
well-defined position in front of his cage and feeding him whenever he
did scratch himself I got him to always scratch within a few seconds
after I took that position.

GENERAL MENTAL DEVELOPMENT OF THE MONKEYS

It is to be hoped that the growing recognition of the worth of
comparative and genetic studies will lead to investigations of the mental
make-up of other species of monkeys, and to the careful overhauling of
the work done so far, including these rather fragmentary studies of mine.
Work with three monkeys of one species, especially when no general body
of phenomena, such as one has at hand in the case of domestic animals,
can be used as a means of comparison, must necessarily be of limited
application in all its details and of insecure application even in its
general features. What I shall say concerning the advance in the mental
development of the monkeys over that of other mammals may then be in
strictness true of only my three subjects, and it may be left to the
judgment of individuals to extend my conclusions as far as seems to them
likely. To me it seems fairly likely that the very general mental traits
which the research has demonstrated hold true with little variation in
the monkeys in general.

The monkeys represent progress in mental development from the generalized
mammalian type toward man:—

1. In their sensory equipment, in the presence of focalized vision.

2. In their motor equipment, in the coördinated movements of the hand and
the eye.

3. In their instincts or inherited nervous connections, in their general
physical and mental activity.

4. In their method of learning or associative processes; in—

_a._ Quicker formation of associations,
_b._ Greater number of associations,
_c._ Greater delicacy of associations,
_d._ Greater complexity of associations,
_e._ Greater permanence of associations.

The fact of (1) is well known to comparative anatomists. Its importance
in mental development is perhaps not realized, but appears constantly to
a systematic student.

(2) is what accounts for much of the specious appearance of human ways
of thinking in the monkeys and becomes in its human extension the handy
tool for much of our intellectual life. It is in great measure the
prerequisite of 4 _c_.

(3) accounts for the rest of such specious appearances, is at the basis
of much of 4 _b_, presages the similar though extended instincts of the
human being, which I believe are the leading efficient causes of human
mental capacity, and is thus the great mental bond which would justify
the inclusion of monkeys and man in a common group if we were to classify
animals on the basis of mental characteristics.

Even the casual observer, if he has any psychological insight, will be
struck by the general, aimless, intrinsically valuable (to the animal’s
feelings) physical activities of a monkey compared with the specialized,
definitely aroused, utilitarian activities of a dog or cat. Watch the
latter and he does but few things, does them in response to obvious
sense presentations, does them with practical consequences of food,
sex-indulgence, preparation for adult battles, etc. If nothing that
appeals to his special organization comes up, he does nothing. Watch a
monkey and you cannot enumerate the things he does, cannot discover the
stimuli to which he reacts, cannot conceive the _raison d’être_ of his
pursuits. Everything appeals to him. He likes to be active for the sake
of activity.

The observer who has proper opportunities and takes proper pains will
find this intrinsic interest to hold of mental activity as well. No. 1
happened to hit a projecting wire so as to make it vibrate. He repeated
this act hundreds of times in the few days following. He did not, could
not, eat, make love to, or get preliminary practice for the serious
battles of life out of, that sound. But it did give him mental food,
mental exercise. Monkeys seem to enjoy strange places; they revel, if I
may be permitted an anthropomorphism, in novel objects. They like to have
feelings as they do to make movements. The fact of mental life is to them
its own reward.

It is beyond question rash for any one to venture hypotheses concerning
the brain parallel of mental conditions, most of all for the ignoramus
in the comparative histology of the nervous system, but one cannot help
thinking that the behavior of the monkeys points to a cerebrum that is
no longer a conservative machine for making a few well-defined sorts of
connections between sense-impressions and acts, that is not only fitted
to do more delicate work in parts, but is also alive, tender all over,
functioning throughout, set off in action by anything and everything. And
if one adds coördinations allowing a freedom and a differentiation of
action of the muscles used in speech comparable to that already present
in connection with the monkey’s hand, he may well ask, “What more of a
nervous mechanism do you need to parallel the behavior of the year-old
child?” However, this is not the place to speculate upon the importance
to human development of our instinctive aimless activity, physical and
mental, or to describe further its similarity and evident phylogenetic
relationship to the instinctive behavior of the monkeys. Elsewhere I
shall undertake that task.

4. In their method of learning, the monkeys do not advance far beyond the
generalized mammalian type, but in their proficiency in that method they
do. They seem at least to form associations very much faster, and they
form very many more. They also seem superior in the delicacy and in the
complexity of the associations formed and the connections seem to be more
permanent.

This progress may seem, and doubtless will to the thinker who looks upon
the human intellect as a collection of functions of which ideation,
judgment and reasoning are chief, to be slight. To my mind it is not
so in reality. For it seems to me highly probable that the so-called
‘higher’ intellectual processes of human beings are but secondary results
of the general function of having free ideas and that this general
function is the result of the formation after the fashion of the animals
of a very great number of associations. I should therefore say, “Let
us not wonder at the comparative absence of free ideas in the monkeys,
much less at the absence of inferences or concepts. Let us not wonder
that the only demonstrable intellectual advance of the monkeys over the
mammals in general is the change from a few, narrowly confined, practical
associations to a multitude of all sorts, for that may turn out to be at
the bottom the only _demonstrable advance of man_, an advance which in
connection with a brain acting with increased delicacy and irritability,
brings in its train the functions which mark off human mental faculty
from that of all other animals.”

The typical process of association described in Chapter II has since been
found to exist among reptiles (by Mr. R. M. Yerkes) and among fishes (by
myself). It seems fairly likely that not much more characterizes the
primates. If such work as that of Lubbock and the Peckhams holds its own
against the critical studies of Bethe, this same process exists in the
insects. Yerkes and Bosworth think they have demonstrated its presence
in the crayfish. Even if we regard the learning of the invertebrates as
problematic, still this process is the most comprehensive and important
thing in mental life. I have already hinted that we ought to turn our
views of human psychology upside down and study what is now casually
referred to in a chapter on habit or on the development of the will, as
the general psychological law, of which the commonly named processes are
derivatives. When this is done, we shall not only relieve human mentality
from its isolation and see its real relationships with other forms; we
may also come to know more about it, may even elevate our psychologies
to the explanatory level and connect mental processes with nervous
activities without arousing a sneer from the logician or a grin from the
neurologist.

CHAPTER VI

LAWS AND HYPOTHESES FOR BEHAVIOR

LAWS OF BEHAVIOR IN GENERAL

_Behavior is predictable._ The first law of behavior, one fraction of
the general law of the uniformity of nature, is that with life and
mind, as with mass and motion, the same cause will produce the same
effect,—that _the same situation will, in the same animal, produce the
same response_,—and that _if the same situation produces on two occasions
two different responses, the animal must have changed_.

Scientific students of behavior will, with few exceptions, accept this
law in theory, but in practice we have not fully used it. We have too
often been content to say that a man may respond in any one of several
ways to the same situation, or may attend to one rather than another
feature of the same object, without insisting that the man must in each
case be different, and without searching for the differences in him which
cause the different reactions.

The changes in an organism which make it respond differently on different
occasions to the same situation range from temporary to permanent
changes. Hunger, fatigue, sleep, and certain diseases on the one hand,
and learning, immunity, growth and senility on the other, illustrate this
range.

Behavior is predictable _without recourse to magical agencies_. It is,
of course, the case that any given difference between the responses
of an animal to the same situation depends upon some _particular_
difference in the animal. Each immunity, for example, has its detailed
representation in an altered condition of the blood or other bodily
tissue. In general the changes in an animal which cause changes in its
behavior to the same situation are fully enumerated in a list of the
bodily changes concerned. That is, whatever changes may be supposed to
have taken place in the animal’s vital force, spiritual essence, or
other magical bases for life and thought, are useless for scientific
explanation and control of behavior.

No competent thinker probably doubts this in the case of such changes
as are referred to by hunger, sleep, fatigue, so-called ‘functional’
diseases and immunity, and those who do doubt it in the case of mental
growth and learning seem to represent an incomplete evolution from
supernatural, or rather infrascientific, thinking. There may be in
behavior a surplus beyond what would be predictable if the entire history
of every atom in the body was known—a surplus necessarily attributable to
changes in the animal’s incorporeal structure. But scientific thinkers
properly refuse to deliberately count upon such a surplus.

_Every response or change in response of an animal is then the result of
the interaction of its original knowable nature and the environment._
This may seem too self-evident a corollary for mention. It should be
so, but, unfortunately, it is not. Two popular psychological doctrines
exist in defiance of it. One is the doctrine that the movements of early
infancy are random, the original nature of the animal being entirely
indifferent as to what movement shall be made upon a given stimulus. But
no animal can have an original nature that does not absolutely prescribe
just what the response shall be to every stimulus. If the movements are
really random, they occur by virtue of some force that works at random.
If the movements are really the result of the action of the environment
on the animal’s nature, they are never random. A baby twiddles his thumbs
or waves his legs for exactly the same sort of reason that a chick pecks
at a worm or preens its wing.

The other doctrine which witnesses to neglect of the axiom that behavior
is the creation of the environment, acting on the animal’s nature, is the
doctrine that the need for a certain behavior helps to create it, that
being in a difficulty tends in and of itself to make an animal respond so
as to end the difficulty.

The truth is that to a difficulty the animal responds by whatever its
inherited and acquired nature has connected with the special form of
difficulty and that in many animals the one response of those thus
provided which relieves the difficulty is selected and connected more
firmly with that difficulty’s next appearance. The difficulty acts only
as a stimulus to the animal’s nature and its relief acts only as a
premium to the connection whereby it was relieved. The law of original
behavior, or the law of instinct, is then that _to any situation an
animal will, apart from learning, respond by virtue of the inherited
nature of its reception-, connection- and action-systems_.

The inquiry into the laws of learning to be made in this essay is limited
to those aspects of behavior which the term has come historically to
signify, that is, to intellect, skill, morals and the like.

For the purposes of this essay it is not necessary to decide just what
features of an animal’s behavior to include under intellect, skill,
morals and the like. The statements to be made will fit any reasonable
dividing line between behavior on the one side and mere circulation,
digestion, excretion and the like on the other. There should in fact
be no clear dividing line, since there is no clear gap between those
activities which naturalists have come to call behavior and the others.

The discussion will include: First, a description of two laws of
learning; second, an argument to prove that no additional forces
are needed—that these two laws explain all learning; and third, an
investigation of whether these two laws are reducible to more fundamental
laws. I shall also note briefly the consequences of the acceptance of
these laws in one sample case, that of the study of mental evolution.

PROVISIONAL LAWS OF ACQUIRED BEHAVIOR OR LEARNING

The Law of Effect is that: _Of several responses made to the same
situation, those which are accompanied or closely followed by
satisfaction to the animal will, other things being equal, be more firmly
connected with the situation, so that, when it recurs, they will be
more likely to recur; those which are accompanied or closely followed
by discomfort to the animal will, other things being equal, have their
connections with that situation weakened, so that, when it recurs, they
will be less likely to occur. The greater the satisfaction or discomfort,
the greater the strengthening or weakening of the bond._

The Law of Exercise is that: _Any response to a situation will, other
things being equal, be more strongly connected with the situation in
proportion to the number of times it has been connected with that
situation and to the average vigor and duration of the connections._

These two laws stand out clearly in every series of experiments on animal
learning and in the entire history of the management of human affairs.
They give an account of learning that is satisfactory over a wide range
of experience, so long as all that is demanded is a rough and general
means of prophecy. We can, as a rule, get an animal to learn a given
accomplishment by getting him to accomplish it, rewarding him when he
does, and punishing him when he does not; or, if reward or punishment are
kept indifferent, by getting him to accomplish it much oftener than he
does any other response to the situation in question.

For more detailed and perfect prophecy, the phrases ‘result in
satisfaction’ and ‘result in discomfort’ need further definition, and the
other things that are to be equal need comment.

By a satisfying state of affairs is meant one which the animal does
nothing to avoid, often doing such things as attain and preserve it. By a
discomforting or annoying state of affairs is meant one which the animal
commonly avoids and abandons.

The satisfiers for any animal in any given condition cannot be determined
with precision and surety save by observation. Food when hungry, society
when lonesome, sleep when fatigued, relief from pain, are samples of the
common occurrence that what favors the life of the species satisfies its
individual members. But this does not furnish a completely valid rule.

The satisfying and annoying are not synonymous with favorable and
unfavorable to the life of either the individual or the species. Many
animals are satisfied by deleterious conditions. Excitement, overeating,
and alcoholic intoxication are, for instance, three very common and very
potent satisfiers of man. Conditions useful to the life of the species
in moderation are often satisfying far beyond their useful point: many
conditions of great utility to the life of the species do not satisfy and
may even annoy its members.

The annoyers for any animal follow the rough rule that alterations
of the animal’s ‘natural’ or ‘normal’ structure—as by cuts, bruises,
blows, and the like,—and deprivations of or interference with its
‘natural’ or ‘normal’ activities,—as by capture, starvation, solitude,
or indigestion,—are intolerable. But interference with the structure
and functions by which the species is perpetuated is not a sufficient
criterion for discomfort. Nature’s adaptations are too crude.

Upon examination it appears that the pernicious states of affairs which
an animal welcomes are not pernicious _at the time, to the neurones_. We
learn many bad habits, such as morphinism, because there is incomplete
adaptation of all the interests of the body-state to the temporary
interest of its ruling class, the neurones. So also the unsatisfying
goods are not goods to the neurones at the time. We neglect many benefits
because the neurones choose their immediate advantage. The neurones must
be tricked into permitting the animal to take exercise when freezing or
quinine when in a fever, or to free the stomach from certain poisons.

Satisfaction and discomfort, welcoming and avoiding, thus seem to be
related to the maintenance and hindrance of the life processes of the
neurones rather than of the animal as a whole, and to temporary rather
than permanent maintenance and hindrance.

The chief life processes of a neurone concerned in learning are
absorption of food, excretion of waste, reception and conduction of the
nerve impulse, and modifiability or change of connections. Of these only
the latter demands comment.

The connections formed between situation and response are represented by
connections between neurones and neurones, whereby the disturbance or
neural current arising in the former is conducted to the latter across
their synapses. The strength or weakness of a connection means the
greater or less likelihood that the same current will be conducted from
the former to the latter rather than to some other place. The strength or
weakness of the connection is a condition of the synapse. What condition
of the synapse it is remains a matter for hypothesis. Close connection
might mean protoplasmic union, or proximity of the neurones in space, or
a greater permeability of a membrane, or a lowered electrical resistance,
or a favorable chemical condition of some other sort. Let us call
this undefined condition which parallels the strength of a connection
between situation and response the intimacy of the synapse. Then the
modifiability or connection changing of a neurone equals its power to
alter the intimacy of its synapses.

As a provisional hypothesis to account for what satisfies and what annoys
an animal, I suggest the following:—

A neurone modifies the intimacy of its synapses so as to keep intimate
those by whose intimacy its other life processes are favored and to
weaken the intimacy of those whereby its other life processes are
hindered. The animal’s action-system as a whole consequently does nothing
to avoid that response whereby the life processes of the neurones other
than connection-changing are maintained, but does cease those responses
whereby such life processes of the neurones are hindered.

This hypothesis has two important consequences. First: Learning by
the law of effect is then more fully adaptive for the neurones in the
changing intimacy of whose synapses learning consists, than for the
animal as a whole. It is adaptive for the animal as a whole only in so
far as his organization makes the neurones concerned in the learning
welcome states of affairs that are favorable to his life and that of his
species and reject those that are harmful.

Second: A mechanism in the neurones gives results in the behavior of
the animal as a whole that seem beyond mechanism. By their unmodifiable
abandonment of certain specific conditions and retention of others, the
animal as a whole can modify its behavior. Their one rule of conduct
causes in him a countless complexity of habits. The learning of an animal
is an instinct of its neurones.

I have limited the discussion to animals in whom the connection-system
is a differentiated organ, the neurones. In so far as the law of effect
operates in an animal whose connection-system is not anatomically
distinguishable and is favored and hindered in its life by the same
conditions that favor and hinder the life of the animal as a whole,
the satisfying and annoying will be those states of affairs which the
connection-system, whatever it be, maintains and abandons.

The other things that have to be equal in the case of the law of effect
are: First, the frequency, energy and duration of the connection,—that
is, the action of the law of exercise; second, the closeness with which
the satisfaction is associated with the response; and, third, the
readiness of the response to be connected with the situation.

The first of these accessory conditions requires no comment. A slightly
satisfying or indifferent response made often may win a closer connection
than a more satisfying response made only rarely.

The second is most clearly seen in the effect of increasing the interval
between the response and the satisfaction or discomfort. Such an increase
diminishes the rate of learning. If, for example, four boxes were
arranged so that turning a button caused a door to open (and permit a cat
to get freedom and food) in one, five, fifty and five hundred seconds,
respectively, a cat would form the habit of prompt escape from the first
box most rapidly and would almost certainly never form that habit in the
case of the fourth. The electric shock administered just as an animal
starts on the wrong path or touches the wrong mechanism, is potent, but
the same punishment administered ten or twenty seconds after an act will
have little or no effect upon that act.

Close temporal sequence is not the only means of insuring the connection
of the satisfaction with the response producing it. What is called
attention to the response counts also. If a cat pushes a button around
with its nose, while its main occupation, the act to which its general
‘set’ impels it, to which, we say, it is chiefly attentive, is that of
clawing at an opening, it will be less aided in the formation of the
habit than if it had been chiefly concerned in what its nose was doing.
The successful response is as a rule only a part of all that the animal
is doing at the time. In proportion as it is an eminent, emphatic part of
it, learning is aided. Similarly discomfort eliminates most the eminent,
emphatic features of the total response which it accompanies or shortly
follows.

The third factor, the susceptibility of the response and situation to
connection, is harder to illustrate. But, apparently, of those responses
which are equally strongly connected with a situation by nature and
equally attended to, some are more susceptible than others to a more
intimate connection.

The things which have to be equal in the case of the law of exercise
are the force of satisfyingness; that is, the action of the law of
effect, and again the readiness of the response to be connected with the
situation.

The operation of the laws of instinct, exercise and effect is
conditioned further by (1) what may be called the law of assimilation or
analogy,—that a situation, especially one to which no particular response
is connected by original nature or previous experience, may connect with
whatever response is bound to some situation _much like it_,—and (2) by
the law of partial activity—that more or less of the total situation may
be specially active in determining the response.

The first of these laws is a result of the facts that conduction in the
neurones follows the line of least resistance or closest connection, that
the action-system is so organized that certain responses tend to be made
in their totality if at all, and that slightly different situations may,
therefore, produce some one response, the effects of their differences
being in the accessories of that response.

The second law is a result of the facts that the situation, itself a
compound, produces a compound action in the neurones, and that by reason
of inner conditions, the relative intensities of different parts of the
compound may vary. The commonest response will be that due to the modal
condition of the neural compound, but every condition of the compound
will have its response.

THE ADEQUACY OF THE LAWS OF EXERCISE AND EFFECT

Behavior has been supposed to be modified in accordance with three
other principles or laws besides the law of exercise and the law of
effect. Imitation is often used as a name for the supposed law that the
perception of a certain response to a situation by another animal tends
in and of itself to connect that response to that situation. Common
acceptance has been given to more or less of the law that the idea of an
act, or of the result of an act, or of the immediate or remote sensations
produced by the act, tends in and of itself to produce the act. Such a
law of ‘suggestion’ or ‘ideo-motor’ action may be phrased differently,
but in whatever form, it insists that the bond between a situation and
some conscious representation of a response or of its consequences can do
the work of the bond between the situation and the response itself. In
acts of reasoning man has been supposed to connect with a given situation
a response that could never have been predicted merely from knowledge
of what responses were connected with that situation by his original
nature or had been connected with it by the laws of exercise and effect.
Inference has been supposed to create bonds in and of itself and to be
above the mere laws of habit.

Various forms of statement, most of them vague, have been and would be
used in describing the potency of a perceived response, a thought-of
response, or a train of inference, to produce a response and bind it to
the given total situation. Any forms will do for the present argument,
since all forms mean to assert that responses can be and often are bound
to situations otherwise than by original bodily nature, satisfaction,
discomfort, disuse and use. I shall try to show that they cannot; that,
on the contrary, the laws of exercise and effect account for all learning.

_The facts of imitation in human and animal behavior are explainable by
the laws of instinct, exercise and effect._

Some cases of imitation are undoubtedly mere instincts in which the
situation responded to is an act by another of the same species. If the
baby smiles at a smile, it is because of a special, inborn connection
between that sight and that act,—he smiles at a smile for just the same
reason that he draws down his mouth and wails at harsh words. At that
stage of his life he does not imitate other simple acts. A man runs
_with_ a crowd for the same reason that he runs _from_ a tiger. Returning
a blow is no more due to a general tendency to imitate than warding it
off is.

Other cases of imitation are mere adjuncts to the ordinary process of
habit-formation. In the first place, the act of another, or its result,
may serve as a model by which the satisfyingness of one’s own responses
are determined. Just as the touch and taste of food tells a baby that
he has got it safely into his mouth, so the sound of a word spoken by
another or the sight of another performing some act of skill tells us
whether our pronunciation or technique is right or wrong.

In the second place, the perception of another’s act may serve as a
stimulus to a response whereby the situation is altered into one to
which the animal responds from habit by an act like the one perceived.
For example, the perception of another making a certain response (_A_)
to a situation (_B_) may lead in me by the laws of habit to a response
(_C_) which puts me in a situation (_D_) such that the response (_A_) is
made by me by the laws of habit. Suppose that by previous training the
act of taking off my hat (_A_) has become connected as response to the
situation (_D_), ‘thought of hat off,’ and suppose that with the sight of
others uncovering their heads (_A_) in church (_B_) there has, again by
previous habituation, been connected, as response (_C_), ‘thought of hat
off.’ Then the sight of others uncovering their heads would by virtue of
the laws of habit lead me to uncover. Imitation of this sort, where the
perception of the act or condition in another gives rise to the idea of
performing the act or attaining the condition, the idea in turn giving
rise to the appropriate act, is certainly very common.

There may be cases of imitation which cannot be thus accounted for as
special instinctive responses to the perception of certain acts by the
same acts, as habits formed under the condition that the satisfyingness
of a response is its likeness to the perceived act of another, or as the
connection of two habits, one of getting, from the perceived act of
another, a certain inner condition, the other of getting, from this inner
condition, the act in question. There may be, that is, cases where the
perceived act of another in and of itself creates a connection.

It is apparently taken for granted by a majority of writers on human
behavior that cases of such direct mental infection, as it were, not
only exist, but are the rule. I am unable to find proof of such cases,
however. Those commonly quoted are far from clear. Learning to talk in
the human infant, for example, the stock case of imitation as a direct
means of learning, offers only very weak and dubious evidence. Since
what is true of it holds substantially for the other favored cases for
learning by imitation, I shall examine it at some length.

Let us first be clear as to the alternative explanations of linguistic
imitation. The first is that seeing the movements of another’s
mouth-parts or hearing a series of word-sounds in and of itself produces
the response of making that series of sounds or one like it.

The other is that the laws of instinct and habit are adequate to explain
the fact in the following manner: A child instinctively produces a great
variety of sounds and sound-series. Some of these, accepted as equal to
words by the child’s companions, are rewarded, so that the child learns
by the law of effect to use them in certain situations to attain certain
results. It is possible also that a child instinctively feels a special
satisfaction at babbling when spoken to and a special satisfaction at
finding the sound he makes like one that rings in the ears of memory
and has meaning. The latter would be like the instinctive satisfaction
apparently felt in constructing an object which is like some real object
whose appearance and meaning he knows.

A child also meets frequently the situations ‘say dada,’ ‘say mama,’ ‘say
good night’ and the like,[41] and is rewarded when his general babble
produces something like the word spoken to him. He thus, by the law of
effect, learns to respond to any ‘say’ situation by making _some_ sound
and to each of many ‘say’ situations by making an appropriate sound, and
to feel satisfaction at duplicating these words when heard. According
to the amount of such training, the tendency to respond to words spoken
to him by making some sound may become very strong, and the number of
successful duplications very large. Satisfaction may be so connected
with saying words that the child practices them by himself orally and
even in inner speech. The second alternative relies upon the instinct
of babbling, and the satisfaction of getting desirable effects from
speech, either the effect which the word has by its meaning as a request
(‘water,’ ‘milk,’ ‘take me outdoors’ and the like) or the effect which it
has by its mere sound upon companions who notice, pet or otherwise reward
a child for linguistic progress.

There are many difficulties in the way of accepting the first
alternative. First of all, no one can believe that _all_ of a child’s
speech is acquired by direct imitation. On many occasions the process is
undoubtedly one of the production of many sounds, irrespective of the
model given, and the selection of the best one by parental reward. Any
student who will try to get a child who is just beginning to speak, to
say cat, dog and mouse and will record the sounds actually made by the
child in the three cases, will find them very much alike. There will in
fact be little that even _looks_ like direct imitation until the child
has ‘learned’ at least forty or fifty words.

The second difficulty lies in the fact that different children, in even
the clearest cases of the imitation of one sound, vary from it in so many
directions. A list of all the sounds made in response to one sound heard
is more suggestive of random babble as modified by various habits of
duplicating sounds, than of a direct potency of the model. Ten children
of the same age may, in response to ‘Christmas,’ say, kiss, kissus,
krismus, mus, kim, kimus, kiruss, i-us and even totally unlike vocables
such as hi-yi or ya-ya.

The third difficulty is that in those features of word-sounds which are
hard to acquire, such as the ‘th’ sound, direct imitation is inadequate.
The teacher has recourse to trial and chance success, the spoken word
serving as a model to guide satisfaction and discomfort. In general no
sound not included in the instinctive babble of children seems to be
acquired by merely hearing and seeing it made.

A fourth difficulty is that by the doctrine of direct imitation it should
not be very much more than two or three times as hard to repeat a two-
or three-syllable series as to repeat a single syllable. It is, in fact,
enormously harder. This is, of course, just what is to be expected if
learning a sound means the selection from random babbling plus previous
habits. If, for instance, a child makes thirty monosyllabic sounds
like pa, ga, ta, ma, pi, gi, li, mi, etc., there is, by chance, one
chance in thirty that in response to a word or phrase he will make that
one-syllable sound of his repertory which is most like it, but there is
only one chance in nine hundred that he will make that _two-syllable_
combination of his repertory which is most like it.

On the other hand, two objections will be made to the opposite view that
the word spoken acts only as a model to select from responses otherwise
caused, or as a stimulus to habits already existing. First it will be
said that clear, indubitable repetitions of words never practiced by
the child, either as totals or in their syllables separately, _do_
occur,—that children do respond by repeating a word in cases where full
knowledge of all their previous habits would give no reason to expect
them to make such a connection. To this the only retort is that such
observations should be based on a very delicate and very elaborate record
of a child’s linguistic history, and that until they are so made, it is
wise to withhold acceptance.

The second objection is that the rapid acquisition of a vocabulary
such as occurs in the second and third year is too great a task to be
accomplished by the laws of exercise and effect alone. This objection
is based on an overestimation of the variety of sounds which children
of the ages in question make. For example, a child who says 250 words,
including say 400 syllables, comprising say 300 syllables which, when
properly pronounced, are distinguishable, may actually use less than 50
distinguishable syllables. _Ba_, may stand for the first syllable of
father, water, barn, park and the like. _Ki_ may stand for cry, climb,
and even carry. For a child to say a word commonly means that he makes
a sound which his intimate companions can recognize as his version of
that word. A child who can produce something like each one of a thousand
words upon hearing them, may do so from actual control over less than
a hundred syllables. If we suppose him to have acquired the habits,
first, of saying _something_ in such a case, second, of responding to a
certain hundred sounds when perceived or remembered by making, in each
case, a similar sound, and, third, of responding to any other sound when
perceived or remembered, by making that sound of his own repertory which
is most like it,[42] we can account for a thousand ‘imitations,’ and
still not have made a large demand upon childish powers of learning.

No one should pretend to have disproved direct imitation in the case of
learning to talk until he has subjected all these and other matters to
crucial experiments. But the burden of proof does seem to belong upon
those who deny the adequacy of the laws of exercise and effect. In so far
as the choice is between accepting or rejecting a general law that, other
things being equal, the perception of a response in another produces that
response, we surely must reject it. Some of the cases of imitation may be
unexplained by the laws of exercise and effect. But for others no law of
imitation is required. And of what should happen by such a law not over a
trivial fraction at most does happen.

_The idea of a response is in and of itself unable to produce
that response._

The early students of behavior, considering human behavior and
emphasizing behavior that was thought about and purposive, agreed that
the sure way to connect a response with a situation was to choose, or
will, or consent to, that response. Later students still agreed that
to think about the response in some way, to have an image of it or of
the sensations caused in you by previous performances of it, was a
strong provocative to it. To get a response, get some sort of conscious
representative of it, has been an acceptable maxim. Medicine, education
and even advertising have based their practice upon the theory that ideas
tended to issue in the particular sort of acts that they were ideas of.

The laws of exercise and effect, on the contrary, if they are the sole
laws of modifiability, insist that the thought of an act will produce
that act only if the act has been connected with that thought (and
without resulting discomfort) in the animal’s past.

It seems plausible that there should be a peculiar bond between the
thought of a response and the response. The plausibility is due to two
reasons, one of which is sound but inadequate, the other being, in my
opinion, entirely unsound. The first reason is that, as a mere matter
of fact, the thought of a response does so often produce it. The second
is that an idea of a response seems a natural and sufficient cause for
it to appear. The first reason is inadequate to justify any law of the
production of a response by its image or other representative, since
evidence can be found to show that when a response is produced by an
idea of it, it has been already bound to that idea by repetition or
satisfaction. The second reason is unsound because, even if responses are
brought to pass occasionally by their images, that is surely an extremely
rare and unnatural method.

It is certain that in at least nine cases out of ten a response is
produced, not by an image or other representation of it, but by a
situation nowise like it or any of its accessories. Hunger and the
perception of edible objects, far outweigh ideas of grasping, biting and
swallowing, as causes of the eating done in the world. Objects sensed,
not images of eye-movements, cause a similar overwhelming majority of
the eye’s responses. We walk, reach and grasp on most occasions, not
because of anticipatory images of how it will feel to do so or verbal
descriptions to ourselves of what we are to do, but because we are
stimulated by the perception of some object.

It is also certain that the idea of a response may be impotent to
produce it. I cannot produce a sneeze by thinking of sneezing. A child
may have, in the case of some simple bodily act, which he has done in
response to certain situations thousands of times, as adequate ideas of
it as are possessed by others, and yet be utterly unable to make himself
do it; many adults show this same phenomenon, for instance, in the case
of swallowing a pill. And, of course, one can have ideas of running a
mile in two minutes, jumping a fence eight feet high, or drawing a line
exactly equal to a hundred millimeter line, just as easily as of running
the mile in ten minutes, or jumping four feet.

It is further certain that the thought of doing one thing very often
results in the man’s doing something quite different. The thought of
moving the eyes smoothly without stops along a line of print has occurred
to many people, who nevertheless actually did as a result move the eyes
in a series of jumps with long stops.

It is further certain that in many cases where an animal does connect a
given response with the image or thought of that response, the connection
has been built up by the laws of exercise and effect. Such cases as
appropriate responses to, ‘I will go to bed,’ ‘I will get up,’ ‘I will
eat,’ ‘I will write a letter,’ ‘I will read,’ or to the corresponding
commands, requests or suggestions, are observably built up by training.
The appropriate response follows the idea only if it has, by repetition
or reward, been connected with it or something like it. If the only
requirement in moral education were to have the idea of the right act
at the right time, the lives of teachers and parents would be greatly
alleviated. But the decision to get up, or the idea of getting up or of
being up, is futile until the child has connected therewith the actual
act of getting up.

The defender of the direct potency of conscious representatives of a
response to produce it may be tempted to complain at this point that what
the laws of exercise and effect do is to reduce the strength of competing
ideas, and leave the idea, say of getting up, free to exercise its direct
potency. The complaint shows a weak sense for fact. The ordinary child is
not a Hamlet, nor is he beguiled by the imagined delights of staying in
bed, nor repelled by the image of getting up out of it. On the contrary,
he may be entirely willing to _think of_ getting up. It is the actual
delights that hold him, the actual discomforts that check him, and the
only way to be sure that he will get up is so to arrange matters that it
is more satisfactory to him to get up than not to when the situation,
whatever it be, that is to suggest that response, makes its appearance.

The experience of every schoolroom shows that it is not enough to get the
idea of an act. The act must have gone with that idea or be now put with
it. The bond must be created. Responses to the suggestions of language,
whether addressed to us by others or by ourselves in inner speech, in
a very large majority of cases owe their bonds to the laws of exercise
and effect. We learn to do what we are told, or what we tell ourselves,
by doing _something_ and rejecting or retaining what we do by virtue
of its effects. So also in the case of a majority of responses to the
suggestions of other than verbal imagery.

The idea of a response, like the perception of a response by another,
acts often as a guide to response _ex post facto_ by deciding what shall
be satisfying. Where superficial inspection leaves the impression that
the idea creates the act, a little care often shows it to have only
selected from the acts produced by instinct and habit. For example, let
the reader think of some act never performed hitherto, such as putting
his left middle finger upon the upper right hand corner of this page,
and make the movement. It may seem at first sight that having the idea
entirely unopposed was the sufficient cause of the act. But careful
experiment, including, for instance, the closure of the eyes and
anesthesia of the fingers will reveal that the original propulsion of the
idea is not to just that act, but to many possibilities, and that its
chief potency lies in the fact that not to get the finger to that point
is annoying, and that consequently the organism is at peace only when the
act is done.

So far it has been shown that: The majority of responses are not produced
by ideas of them. The idea of a response may be impotent to produce it.
The idea of one act may produce a different, even an opposite act. When
an idea seems to produce a response in and of itself, it may really act
by determining the satisfyingness of responses otherwise made. These
facts are sufficient to destroy the pretensions of any general law that
the image of an act will, other things being equal, produce it. But the
possibility that such an image may occasionally exercise this peculiar
potency remains.

I despair of convincing the reader that it does not. Man is the
only animal possessing a large fund of ideas of acts, and man’s
connection-system is so complex and his ideas of acts are so intricately
bound to situations that have by use and effect produced those acts,
that the proof of this negative is a practical impossibility. But it is
possible to show that even the most favored cases for the production of a
response by securing an ideal representation of it may be explainable by
use and effect alone.

The extreme apparent potency of ideas representing acts to produce them
regardless of bonds of use or effect is, of course, witnessed in the
phenomena of suggestion in hypnosis and allied states. To try to reduce
these phenomena to consequences of the laws of habit may seem fanatical.
Here, it will be said, are the crucial cases where the idea of an act, if
freed from all effects of opposing ideas, does inevitably produce the act
so far as it is a possibility for the animal’s action-system.

That is precisely what I cannot find proof of.

Efficient suggestions to hypnotized subjects, on the contrary, are often
ambiguous in the sense that they seem as likely to arouse a situation
_to which the act has been bound by the law of habit_ as to arouse an
idea of the act. Often they are far better suited to the former purpose.
Direct commands—Walk, Dance, Get up, Sit down—obviously will operate by
the law of habit provided the situations connected with disobedience are
excluded. This is also the case with such indirect suggestions as ‘This
is a knife (stick).’ ‘This is your sword (broom).’ ‘Have a cigar (a pen).’

The release of a suggestion from inhibitions may as well be the release
from _ideas connected as antecedents with_ not performing the act as
the release from _ideas of_ not performing it. It is a question of fact
whether, to get an act done by the subject, one must arouse in him an
idea to which or to a part of which or to something like which the act
has been bound by use or effect, or may arouse simply an idea of the act.

Finally, if an idea has a tendency to connect with a certain response,
over and above the bonds due to exercise and effect, it should _always_
manifest that tendency. If the connection is not made, it must be due to
the action of some contrary force. It is less my duty to show that the
laws of habit can account for hypnotic suggestibility, obsessions, and
the like, than it is my opponents’ duty to explain why a man can spend a
half day in hospitably welcoming a hundred ideas of acts and yet perform
no one of them, save those in the case of which he has learned to do the
thing when he thinks of doing it. Again, how can the mere addition of
the idea of a future date to the idea of an act so utterly deprive it of
present potency.

In view of all these facts it seems probable that ideas of responses act
in connection just as do any other situations, and that the phenomena of
suggestion and ideo-motor action really mean that any idea will, except
for competing ideas, produce the response, not that _is like it_, but
that _has gone with it_, or with some idea like it.

_Rational connections are, in their causation, like any others,
the difference being in what is connected._

It remains to ask whether situation and response are bound together in
the case of reasoning by any other forces than the forces of repetition,
energy and satisfaction? Do the laws of inferential thinking transcend
the laws of exercise and effect? Or does the mind, even in these novel
and constructive responses, do only what it is forced to do by original
nature or has done without discomfort?

To defend the second alternative involves the reduction of the processes
of abstraction, association by similarity and selective thinking to mere
secondary consequences of the laws of exercise and effect. This I shall
try to do.

The gist of the fact of abstraction is that response may be made to some
elements or aspects of a situation which have never been experienced
in isolation, and may be made to the element in question regardless of
the gross total situation in which it inheres. A baby thus learns to
respond to its mother’s face regardless of what total visual field it is
a part of. A child thus learns to respond by picking out any red object,
regardless of whether the redness be in an apple, a block, a pencil, a
ribbon or a ball. A student thus learns to respond to any plane surface
inclosed by three straight lines regardless of its size, shape, color or
other than geometrical meaning.

What happens in such cases is that the response, by being connected with
many situations alike in the presence of the element in question and
different in other respects, is bound firmly to that element and loosely
to each of its concomitants. Conversely any element is bound firmly to
any one response that is made to all situations containing it and very,
very loosely to each of those responses that are made to only a few of
the situations containing it. The element of triangularity, for example,
is bound firmly to the response of saying or thinking ‘triangle’ but only
very loosely to the response of saying or thinking white, red, blue,
large, small, iron, steel, wood, paper and the like. A situation thus
acquires bonds not only with some response to it as a gross total, but
also with responses to each of its elements that has appeared in any
other gross totals.

Appropriate response to an element regardless of its concomitants is a
necessary consequence of the laws of exercise and effect if an animal
learns to make that response to the gross total situations that contain
the element and not to make it to those that do not. Such prepotent
determination of the response by one or another element of the situation
is no transcendental mystery, but, given the circumstances, a general
rule of all learning. The dog who responds appropriately to ‘beg’ no
matter when, where, or by whom spoken, manifests the same laws of
behavior. There is no difficulty in understanding how each element of a
situation may come to tend to produce a response peculiar to it as well
as to play its part in determining the response to the situation as a
total. There may be some difficulty in understanding how each element
of a situation comes to be _felt_ whereas before only the gross total
was felt. The change in consciousness from the ‘big, blooming, buzzing
confusion’ to an aggregate of well-defined percepts and images, which
accompanies the change in behavior from response to totals to response to
parts or elements, may be mysterious. With the change in consciousness,
however, we are not now concerned. The _behavior_ of man and other
animals toward the abstract elements of color, size, number, form, time
or value is explained by the laws of instinct, exercise and effect.

When the perception or thought of a fact arouses the thought of some
other fact identical in part with the former fact, we have so-called
association by similarity. An element of the neurone-action is prepotent
in determining the succeeding neurone-action. The particular way in which
it determines it is by itself continuing and making connection with other
associates. These it possesses by virtue of the law of exercise and
effect.

* * * * *

The changes in behavior classified under intellect and morality seem
then to be all explainable by the two laws of exercise and effect. The
facts of imitation really refer to certain specific original connections
or to the efficiency of a model in determining what shall satisfy or
to the provision of certain instructive situations in the form of the
behavior of other animals. The facts variously referred to as suggestion,
ideo-motor action or the motor power of ideas, really refer to the fact,
common in the human animal only, that to those ideas that represent acts
in thought the acts are often bound as responses. The bonds are due to
the primary laws of effect and exercise. The facts of reasoning really
refer to the fact of prepotency of one or another element in a situation
in determining the response.

The reduction of all learning to making and rewarding or avoiding and
punishing connections between situation and response allows changes in
intellect and character to be explained by changes in the neurones that
are known either to be or to be possible. I have elsewhere sketched one
such possible neural mechanism for the law of effect.[43]

On the contrary, imitation, suggestion and reasoning, as commonly
described, put an intolerable burden upon the neurones. To any one who
has tried to imagine a possible action in the neurones to parallel the
traditional power of the mere perception of an act in another or of the
mere representation of an act as done by oneself to produce that act,
this is a great merit. For the only adequate psychological parallel of
traditional imitation and suggestion would be the original existence or
the gratuitous formation of a connection between (1) each neurone-action
corresponding to a percept of an act done by another or to the idea of
an act done by oneself and (2) the neurone-action arousing that act. It
is incredible that the neurone-action corresponding to the perception of
a response in another, or to the idea of a response in oneself, or to
the first term in an association by similarity, should have, in and of
itself, a special power to determine that the next neurone-action should
be that paralleling the response in question. And there is no possible
physiological parallel of a power to jump from premise to conclusion for
no other reason than the ideal fitness of the sequence.

SIMPLIFICATIONS OF THE LAWS OF EXERCISE AND EFFECT

There has been one notable attempt to explain the facts of learning by
an even simpler theory than that represented in the laws of exercise
and effect. Jennings has formulated as an adequate account of learning
the law that: “When a certain physiological state has been resolved,
through the continued action of an external agent, or otherwise, into
a second physiological state, this resolution becomes easier, so that
in course of time it takes place quickly and spontaneously” (‘Behavior
of the Lower Organisms,’ p. 289). “The law may be expressed briefly as
follows:—_The resolution of one physiological state into another becomes
easier and more rapid after it has taken place a number of times._ Hence
the behavior primarily characteristic for the second state comes to
follow immediately upon the first state. The operations of this law are,
of course, seen on a vast scale in higher organisms in the phenomena
which we commonly call memory, association, habit formation and learning”
(_ibid._, p. 291). This law may be expressed conveniently as a tendency
of a series of states

A -> B -> C -> D

to become

A -> D

A -> B¹ -> C¹ -> D

B¹ and C¹ being states B and C passed rapidly and in a modified way so
that they do not result in a reaction but are resolved directly into D.

If Professor Jennings had applied to this law the same rigorous analysis
which he has so successfully employed elsewhere, he would have found that
it could be potent to cause learning only if supplemented by the law of
effect and then only for a fraction of learning.

For, the situations being the same, the state A cannot produce, at one
time, now B and, at another time, abbreviated, rudimentary B¹ instead of
B. If A with S produces B once, it must always. If D or a rudimentary B¹
is produced, there must be something other than A; A must itself have
changed. Something must have been added to or subtracted from it. In
Professor Jennings’ own words, “Since the external conditions have not
changed, the animal itself must have changed” (_ibid._, p. 286). And in
adaptive learning something related to the results of the S A connection
must have changed it.

The series A—B—C—D does not become the series A—D or A—B¹—C¹—D by magic.
If B and C are weakened and D is strengthened as sequents of A in
response to S, it is because something other than repetition acts upon
them. Repetition alone could not blow hot for D and cold for B.

Moreover, as a mere matter of fact, “the resolution of one physiological
state into another” through intermediate states does not with enough
repetition “become easier so that in course of time it takes place
quickly and spontaneously.”

Paramecium does not change its response to, say, an obstacle in the
water, from swimming backward, turning to one side and swimming forward
by abbreviating and eventually omitting the turn and the backward
movement. The schoolboy does not tend to count 1, 2, 10 or to say a, b,
z, or give ablative plurals after nominative singulars.

Repetition of a series of physiological states in and of itself on the
contrary makes an animal increasingly _more_ likely to _maintain_ the
series _in toto_. It is hard to give the first and then the last word of
an oft repeated passage like Hamlet’s soliloquy or the Lord’s Prayer, or
to make readily the first and then the last movement of writing a name or
address. Repetition never eliminates absolutely and eliminates relatively
the _less_ often or _less_ emphatically connected.

Even if supplemented by the law of effect, so that some force is at hand
to change the effect of S upon the animal to A D instead of the original
A B C D, the law of the resolution of physiological states would be
relevant to only a fraction of learning. For example, let a cat or dog be
given an ordinary discrimination experiment, but so modified that whether
the animal responds by the ‘right’ or the ‘wrong’ act _he is removed
immediately after the reward or punishment_. That is, the event is either
S R1 or S R2, never S R1 R2. Let the experiment be repeated at intervals
so long that the physiological state, St. R1, or St. R2, leading to the
response R1 or R2 in the last trial, has ceased before the next. The
animal will come to respond to S by R2 only, though R2 has never been
reached by the ‘resolution’ of S R1 R2.

Cats in jumping for birds or mice, men in playing billiards, tennis or
golf, and many other animals in many other kinds of behavior, often learn
as the dog must in this experiment. The situation on different occasions
is followed by different responses, but by only one per occasion.
Professor Jennings was misled by treating as general the special case
where the situation itself includes a condition of discomfort terminable
only by a ‘successful’ response or by the animal’s exhaustion or death.

Assuming as typical this same limited case of response to an annoying
situation, so that success consists simply in replacing the situation
by another, Stevenson Smith reduces the learning-process to the law of
exercise alone. He argues that,—

“For instance, let an organism at birth be capable of giving N reactions
(a, b, c, ... N) to a definite stimulus S and let only one of these
reactions be appropriate. If only one reaction can be given at a time
and if the one given is determined by the state of the organism at the
time S is received, there is one chance in N that it is the appropriate
reaction. When the appropriate reaction is finally given, the other
reactions are not called into play, S may cease to act, but until the
appropriate reaction is given let the organism be such that it runs
through the gamut of the others until the appropriate reaction is brought
about. As there are N possible reactions, the chances are that the
appropriate reaction will be given before all N are performed. At the
next appearance of the stimulus, which we may call S₂, those reactions
which were in the last case performed, are, through habit, more likely to
be again brought about than those which were not performed. Let _u_ stand
for the unperformed reactions. Then we have N - _u_ probable reactions
to S₂. Habit rendering the previously most performed reactions the most
probable throughout we should expect to find the appropriate reaction in
response to

S₁ contained in N.
S₂ contained in N - _u₁_.
S₃ contained in N - _u₁_ - _u₂_.
...
S_ₙ_ contained in N - _nu_, which approaches _one_ as a limit.

Thus the appropriate reaction would be fixed through the laws of chance
and habit. This law of habit is that when any action is performed
a number of times under certain conditions, it becomes under those
conditions more and more easily performed” (_Journal of Comparative
Neurology and Psychology_, 1908, Vol. XVIII, pp. 503-504).

This hypothesis is, like Professor Jennings’, adequate to account for
only the one special case, and is adequate to account for that only
upon a further limitation of the number of times that the animal may
repeat any one of his varied responses to the situation before he has
gone through them all once, or reached the one that puts an end to the
situation.

The second limitation may be illustrated in the simple hypothetical case
of three responses, 1, 2 and 3, of which No. 2 is successful. Suppose the
animal always to go through his repertory with _no_ repetitions until he
reaches 2 and so closes the series.

Only the following can happen:—

1 2
1 3 2
2
2
3 1 2
3 2

and, in the long run, 2 will happen twice as often as 1 or 3 happens.

Suppose the animal to repeat each response of his repertory six times
before changing to another, the remaining conditions being as above. Then
only the following can happen:—

1 1 1 1 1 1 2
1 1 1 1 1 1 3 3 3 3 3 3 2
2
2
3 3 3 3 3 3 1 1 1 1 1 1 2
3 3 3 3 3 3 2,

and in the long run 2 will happen one third as often as 1 or 3 and,
though always successful, must, by Smith’s theory, appear later and
later, so that if the animal meets the situation often enough, he will
eventually fail utterly in it!

Animals do, as a matter of fact, commonly repeat responses many times
before changing them,[44] so that if only the law of exercise operated,
learning would not be adaptive. It is the _effect_ of 2 that gives it the
advantage over 1 and 3. Of two responses to the same annoying situation,
one continuing and the other relieving it, an animal could never learn to
adopt the latter as a result of the law of exercise alone, if the former
was, originally, twice as likely to occur. 1 1 2 would occur as often
as 2 and exercise would be equal for both. The convincing cases are, of
course, those where learning equals the strengthening to supremacy of an
originally very weak connection and the weakening of originally strong
bonds. An animal’s original nature may lead it to behave as shown below:—

1 1 1 3 1 1 4 1 1 2
1 1 1 1 3 1 1 1 3 1 1 4 2
4 1 1 3 3 1 1 4 4 1 1 1 1 1 2, etc.,

and yet the animal’s eventual behavior may be to react to the situation
always by 2. The law of effect is primary, irreducible to the law of
exercise.

THE EVOLUTION OF BEHAVIOR

The acceptance of the laws of exercise and effect as adequate accounts of
learning would make notable differences in the treatment of all problems
that concern learning. I shall take, to illustrate this, the problem of
the development of intellect and character in the animal series, the
phylogenesis of intellectual and moral behavior.

The difficulties in the way of understanding the evolution of
intellectual and moral behavior have been that neither what had been
evolved nor that from which it had been evolved was understood.

The behavior of the higher animals, especially man, was thought to be
a product of impulses and ideas which got into the mind in various
ways and had power to arouse certain acts and other ideas more or
less mysteriously, in the manner described by the laws of ideo-motor
action, attention, association by contiguity, association by similarity,
suggestion, imitation, dynamo-genesis and the like, with possibly a
surplus of acts and ideas due to ‘free will.’ The mind was treated as
a crucible in which a multifarious solution of ideas, impulses and
automatisms boiled away, giving off, as a consequence of a subtle
chemistry, an abundance of thoughts and movements. Human behavior was
rarely viewed from without as a series of responses bound in various
ways to a series of situations. The student of animal behavior passed as
quickly as might be from such mere externals to the inner life of the
creature, making it his chief interest to decide whether it had percepts,
memories, concepts, abstractions, ideas of right and wrong, choices,
a self, a conscience, a sense of beauty. The facts in intellect and
character that are due to learning, that are not the inherited property
of the species and that consequently are beyond the scope of evolution
in the race, were not separated off from the facts of original nature.
The comparative psychologist misspent his energy on such problems as the
phylogenesis of the idea of self, moral judgments, or the sentiment of
filial affection.

At the other extreme, the behavior of the protozoa was either
contemplated in the light of futile analogies,—for instance, between
discriminative reactions and conscious choice, and between inherited
instincts and memory,—or studied crudely in its results without
observation of what the animals really did. The protozoa were regarded
either as potential ‘conscious selves’ or as drifting lumps turned hither
and thither by the direct effects of light, heat, gravity and chemical
forces upon their tissues.

The evolution of the intellectual and moral nature which a higher animal
really possesses from the sort of a nature which the real activities of
the protozoa manifest, is far less difficult to explain.

In so far as the higher animal is a collection of original tendencies
to respond to physical events without and within the body, subject to
modification by the laws of exercise and effect and by these alone,
and in so far as the protozoan is already possessed of a well-defined
repertory of responses connected with physical events without and within
the body in substantially the manner of the higher animal’s original
tendencies, the problems of the evolution of behavior are definite and in
the way of solution.

The previous sections gave reason for the belief that the higher animals,
including man, manifest no behavior beyond expectation from the laws
of instinct, exercise and effect. The human mind was seen to do no
more than connect in accord with original bonds, use and disuse, and
the satisfaction and discomfort resulting to the neurones. The work
of Jennings has shown that the protozoa already possess full-fledged
instincts, homologous with the instincts of man. They too may have
specialized receptors, an action-system with a well-defined repertory and
a connecting system or means of influencing the bonds between the stimuli
received and the motor reactions made. The difficulties of tracing the
possible development of a super-man from an infra-animal thus disappear.

There is, of course, an abundance of _bona fide_ difficulty in
discovering the unlearned behavior of each group of animals and in
tracing, throughout the animal series, changes in the physical events to
which animals are sensitive so that to each a different response may be
attached, changes in the movements of which animals are capable, and
changes in the bonds by which particular movements follow particular
physical events. To find when and how animals whose natures remained
nearly or quite unchanged by the satisfying and annoying effects of their
behavior, gave birth to animals that could learn, is perhaps a still
harder task. But these tasks concern problems that are intelligible
matters of fact. They do not require a student to get out of matter
something defined as beyond matter, or to get volition out of tropisms,
or to get ideas of space and time out of swimming and sleeping.

The evolution of the sensitivities and of the action-systems of animals
has already been subjected to matter-of-fact study by naturalists. The
evolution of the connection-system will soon be. Each reflex, instinct
or capacity, each bond between a given situation presented to a given
physiological state and a given response, has its ancestral tree.
Scratching at an irritated spot on the skin is older than arms. Following
an object that is moving slowly does not have to be explained separately,
as a ‘chance’ variation in dogs, sheep and babies. The mechanical trades
of man are related to the miscellaneous manipulations of the apes. Little
as we know of the connection-systems possessed by animals, we know enough
to be sure that a bond between situation and response has ancestors and
children as truly as does any bodily organ. Professor Whitman a decade
ago showed the possibility of phylogenetic investigation of instinctive
connections in a study which should be a stimulus and model for many
others. In place of any further general account of the study of the
phylogeny of the connection-system, I shall quote from his account of the
concrete phylogeny of the instinct of incubation.

“_b. The Incubation Instinct_

1. _Meaning to be Sought in Phyletic Roots._—It seems quite
natural to think of incubation merely as a means of providing
the heat needed for the development of the egg, and to assume
that the need was felt before the means was found to meet it.
Birds and eggs are thus presupposed, and as the birds could
not have foreseen the need, they could not have hit upon the
means except by accident. Then, what an infinite amount of
chancing must have followed before the first ‘cuddling’ became
a habit, and the habit a perfect instinct! We are driven to
such preposterous extremities as the result of taking a purely
casual feature to start with. Incubation supplies the needed
heat, but that is an incidental utility that has nothing to do
with the nature and origin of the instinct. It enables us to
see how natural selection has added some minor adjustments, but
explains nothing more. For the real meaning of the instinct we
must look to its phyletic roots.

If we go back to animals standing near the remote ancestors of
birds, to the amphibia and fishes, we find the same instinct
stripped of its later disguises. Here one or both parents
simply remain over or near the eggs and keep a watchful guard
against enemies. Sometimes the movements of the parent serve to
keep the eggs supplied with fresh water, but aëration is not
the purpose for which the instinct exists.

2. _Means Rest and Incidental Protection to Offspring._—The
instinct is a part of the reproductive cycle of activities,
and always holds the same relation in all forms that exhibit
it, whether high or low. It follows the production of eggs,
or young, and means primarily, as I believe, rest, with
incidental protection to offspring. That meaning is always
manifest, no less in worms, molluscs, crustacea, spiders and
insects, than in fishes, amphibia, reptiles and birds. The
instinct makes no distinction between eggs and young, and that
is true all along the line up to birds, which extend the same
blind instinct to one as to the other.

3. _Essential Elements of the Instinct._—Every essential
element in the instinct of incubation was present long
before the birds and eggs arrived. These elements are:
(1) the disposition to remain with or over the eggs; (2)
the disposition to resist and drive away enemies; and (3)
periodicity. The birds brought all these elements along in
their congenital equipment, and added a few minor adaptations,
such as cutting the period of incubation to the need of normal
development, and thus avoiding indefinite waste of time in case
of sterile or abortive eggs.

(1) _Disposition to Remain over the Eggs._—The disposition to
remain over the eggs is certainly very old, and is probably
bound up with the physiological necessity for rest after a
series of activities tending to exhaust the whole system. If
this suggestion seems far-fetched, when thinking of birds, it
will seem less so as we go back to simpler conditions, as we
find them among some of the lower invertebrate forms, which are
relatively very inactive and predisposed to remain quiet until
impelled by hunger to move. Here we find animals remaining
over their eggs, and thus shielding them from harm, from sheer
inability or indisposition to move. That is the case with
certain molluscs (_Crepidula_), the habits and development of
which have been recently studied by Professor Conklin. Here
full protection to offspring is afforded without any exertion
on the part of the parent, in a strictly passive way that
excludes even any instinctive care. In _Clepsine_ there is a
manifest unwillingness to leave the eggs, showing that the
disposition to remain over them is instinctive. If we start
with forms of similar sedentary mode of life, it is easy to see
that remaining over the eggs would be the most likely thing
to happen, even if no instinctive regard for them existed.
The protection afforded would, however, be quite sufficient
to insure the development of the instinct, natural selection
favoring those individuals which kept their position unchanged
long enough for the eggs to hatch.”[45]

Professor Whitman proceeds to study the ‘Disposition to Resist
Enemies’ and the ‘Periodicity’ in the same genetic way.

The most important of all original abilities is the ability to learn. It,
like other capacities, has evolved. The animal series shows a development
from animals whose connection-system suffers little or no permanent
modification by experience to animals whose connections are in large
measure created by use and disuse, satisfaction and discomfort.

Some of this development can be explained without recourse to differences
in mere power to learn, by the fact that the latter animals are given
greater stimuli to or rewards for learning. But part of it is due to
differences in sheer ability to learn, that is, in the power of equally
satisfying conditions to strengthen or of equally annoying conditions to
weaken bonds in the animals’ connection-systems. This may be seen from
the following simple and partial case:—

Call 1 and 2 two animals.

Call C₁ and C₂ the internal conditions of the two animals except for
their connection-systems, each being the average condition of the animal
in question.

Call S₁ and S₂ two external states of affairs, each being near the
indifference point for the animal in question,—that is, being one which
the animal does little to either avoid or secure.

Call G₁ and G₂ two responses which result in O₁ and O₂ the _optima_ or
most satisfying state of affairs for 1 and 2.

Call I₁ and I₂ two responses which result in the continuation of S₁ and
S₂.

The only responses possible for 1 are G₁ and I₁.

The only responses possible for 2 are G₂ and I₂.

Animal 1 upon the recurrence of S₁ and C₁ is little or no more likely to
respond by G₁ than he was before.

Animal 2 upon the recurrence of S₂ and C₂ is far more likely to respond
by G₂ than he was before.

The fact thus outlined might conceivably be due to an intrinsic
inequality between O₁ and O₂, the power of equally satisfying _optima_ to
influence, their antecedents being identical. This is not the case in the
evolution of learning, however. For even if, instead of O₂, we had only
a moderately satisfying state of affairs, such as the company of other
chicks to (2) a 15-day-old chick, while O₁ was the optimum of darkness,
dampness, coolness, etc., for (1) an earthworm, 2 would learn far, far
more rapidly than 1.

The fact is due, of course, to the unequal power of equally satisfying
conditions to influence their antecedents. The same argument holds good
for the influence of discomfort.

The ability to learn,—that is, the possession of a connection-system
subject to the laws of exercise and effect,—has been found in animals as
‘low’ as the starfish and perhaps in the protozoa. It is hard to tell
whether the changed responses observed in Stentor by Jennings and in
Paramecium by Stevenson Smith are easily forgotten learnings or long
retained excitabilities. Sooner or later clear learning appears, and
then, from crabs to fish and turtle, from these to various birds and
mammals, from these to monkeys, and from these to man, a fairly certain
increase in sheer ability to learn, in the potency of a supposedly
constant degree of satisfyingness or annoyingness to influence the
connection preceding it, can be assumed. We cannot, of course, define
just what we mean by equal satisfyingness to a mouse and a man, but the
argument is substantially the same as that whereby we assume that the
gifted boy has more sheer ability to learn than the idiot, so that if
the two made the same response to the same situation and were equally
satisfied thereby, the former would form the habit more firmly.

We may, therefore, expect that when knowledge of the structure and
behavior of the neurones comprising the connection-systems of animals (or
of the neurones’ predecessors in this function) progresses far enough
to inform us of just what happens when a connection is made stronger or
weaker and of just what effects satisfying and annoying states of affairs
exert upon the connection-system (and in particular upon the connections
most recently in activity) the ability to learn will show as true an
evolution as the ability to sneeze, oppose the thumb, or clasp an object
touched by the hand.

If my analysis is true, the evolution of behavior is a rather simple
matter. Formally the crab, fish, turtle, dog, cat, monkey and baby have
very similar intellects and characters. All are systems of connections
subject to change by the law of exercise and effect. The differences
are: first, in the concrete particular connections, in _what_ stimulates
the animal to response, _what_ responses it makes, _which_ stimulus
connects with _which_ response, and second, in the degree of ability to
learn—in the amount of influence of a given degree of satisfyingness or
annoyingness upon the connection that produced it.

The peculiarly human features of intellect and character, responses to
elements and symbols, are the results of: first, a receiving system that
is easily stimulated by the external world bit by bit (as by focalized
vision and touch with the moving hand) as well as in totals composed
of various aggregates of these bits; second, of an action-system of
great versatility (as in facial expression, articulation, and the
hands’ movements); and third, of a connection-system that includes the
connections roughly denoted by babbling, manipulation, curiosity, and
satisfaction at activity, bodily or mental, for its own sake; that is
capable of working in great detail, singling out elements of situations
and parts of responses; and that allows satisfying and annoying states of
affairs to exert great influence on their antecedent connections. Because
he learns fast and learns much, in the animal way, man seems to learn by
intuitions of his own.

CHAPTER VII

THE EVOLUTION OF THE HUMAN INTELLECT[46]

To the intelligent man with an interest in human nature it must often
appear strange that so much of the energy of the scientific world has
been spent on the study of the body and so little on the study of the
mind. ‘The greatest thing in man is mind,’ he might say, ‘yet the least
studied.’ Especially remarkable seems the rarity of efforts to trace the
evolution of the human intellect from that of the lower animals. Since
Darwin’s discovery, the beasts of the field, the fowl of the air and
the fish of the sea have been examined with infinite pains by hundreds
of workers in the effort to trace our physical genealogy, and with
consummate success; yet few and far between have been the efforts to find
the origins of intellect and trace its progress up to human faculty. And
none of them has achieved any secure success.

It may be premature to try again, but a somewhat extended series of
studies of the intelligent behavior of fishes, reptiles, birds and
mammals, including the monkeys, which it has been my lot to carry out
during the last five years, has brought results which seem to throw light
on the problem and to suggest its solution.

Experiments have been made on fishes, reptiles, birds and various
mammals, notably dogs, cats, mice and monkeys, to see how they learned
to do certain simple things in order to get food. All these animals
manifest fundamentally the same sort of intellectual life. Their learning
is after the same general type. What that type is can be seen best from
a concrete instance. A monkey was kept in a large cage. Into the cage
was put a box, the door of which was held closed by a wire fastened to
a nail which was inserted in a hole in the top of the box. If the nail
was pulled up out of the hole, the door could be pulled open. In this
box was a piece of banana. The monkey, attracted by the new object,
came down from the top of the cage and fussed over the box. He pulled
at the wire, at the door, and at the bars in the front of the box. He
pushed the box about and tipped it up and down. He played with the nail
and finally pulled it out. When he happened to pull the door again, of
course it opened. He reached in and got the food inside. It had taken
him 36 minutes to get in. Another piece of food being put in and the
door closed, the occurrences of the first trial were repeated, but there
was less of the profitless pulling and tipping. He got in this time in
2 minutes and 20 seconds. With repeated trials the animal finally came
to drop entirely the profitless acts and to take the nail out and open
the door as soon as the box was put in his cage. He had, we should say,
learned to get in.

The process involved in the learning was evidently a process of
selection. The animal is confronted by a state of affairs or, as we may
call it, a ‘situation.’ He reacts in the way that he is moved by his
innate nature or previous training to do, by a number of acts. These
acts include the particular act that is appropriate and he succeeds. In
later trials the impulse to this one act is more and more stamped in,
this one act is more and more associated with that situation, is selected
from amongst the others by reason of the pleasure it brings the animal.
The profitless acts are stamped out; the impulses to perform them in
that situation are weakened by reason of the positive discomfort or the
absence of pleasure resulting from them. So the animal finally performs
in that situation only the fitting act.

Here we have the simplest and at the same time the most widespread sort
of intellect or learning in the world. There is no reasoning, no process
of inference or comparison; there is no thinking about things, no putting
two and two together; there are no ideas—the animal does not think of
the box or of the food or of the act he is to perform. He simply comes
after the learning to feel like doing a certain thing under certain
circumstances which before the learning he did not feel like doing. Human
beings are accustomed to think of intellect as the power of having and
controlling ideas and of ability to learn as synonymous with ability to
have ideas. But learning by having ideas is really one of the rare and
isolated events in nature. There may be a few scattered ideas possessed
by the higher animals, but the common form of intelligence with them,
their habitual method of learning, is not by the acquisition of ideas,
but by the selection of impulses.

Indeed this same type of learning is found in man. When we learn to drive
a golf ball or play tennis or billiards, when we learn to tell the price
of tea by tasting it or to strike a certain note exactly with the voice,
we do not learn in the main by virtue of any ideas that are explained
to us, by any inferences that we reason out. We learn by the gradual
selection of the appropriate act or judgment, by its association with the
circumstances or situation requiring it, in just the way that the animals
do.

From the lowest animals of which we can affirm intelligence up to man
this type of intellect is found. With it there are in the mammals obscure
traces of the ideas which come in the mental life of man to outweigh
and hide it. But it is the basal fact. As we follow the development of
animals in time, we find the capacity to select impulses growing. We find
the associations thus made between situation and act growing in number,
being formed more quickly, lasting longer and becoming more complex
and more delicate. The fish can learn to go to certain places, to take
certain paths, to bite at certain things and refuse others, but not much
more. It is an arduous proceeding for him to learn to get out of a small
pen by swimming up through a hole in a screen. The monkey can learn to do
all sorts of things. It is a comparatively short and easy task for him
to learn to get into a box by unhooking a hook, pushing a bar around and
pulling out a plug. He learns quickly to climb down to a certain place
when he sees a letter T on a card and to stay still when he sees a K. He
performs the proper acts nearly as well after 50 days as he did when they
were fresh in his mind.

This growth in the number, speed of formation, permanence, delicacy and
complexity of associations possible for an animal reaches its acme in the
case of man. Even if we leave out of question the power of reasoning,
the possession of a multitude of ideas and abstractions and the power of
control over impulses, purposive action, man is still the intellectual
leader of the animal kingdom by virtue of the superior development
in him of the power of forming associations between situations or
sense-impressions and acts, by virtue of the degree to which the mere
learning by selection possessed by all intelligent animals has advanced.
In man the type of intellect common to the animal kingdom finds its
fullest development, and with it is combined the hitherto nonexistent
power of thinking about things and rationally directing action in accord
with thought.

Indeed it may be that this very reason, self-consciousness and
self-control which seem to sever human intellect so sharply from that
of all other animals are really but secondary results of the tremendous
increase in the number, delicacy and complexity of associations which the
human animal can form. It may be that the evolution of intellect has no
breaks, that its progress is continuous from its first appearance to its
present condition in adult civilized human beings. If we could prove that
what we call ideational life and reasoning were not new and unexplainable
species of intellectual life but only the natural consequences of an
increase in the number, delicacy, and complexity of associations of
the general animal sort, we should have made out an evolution of mind
comparable to the evolution of living forms.

In 1890 William James wrote, “The more sincerely one seeks to trace the
actual course of psychogenesis, the steps by which as a race we may have
come by the peculiar mental attributes which we possess, the more clearly
one perceives ‘the slowly gathering twilight close in utter dark.’” Can
we perhaps prove him a false prophet? Let us first see if there be any
evidence that makes it probable that in some way or another the mere
extension of the animal type of intellect has produced the human sort. If
we do, let us proceed to seek a possible account of _how_ this might have
happened, and finally to examine any evidence that shows this possible
‘how’ to have been the real way in which human reason has evolved.

It has already been shown that in the animal kingdom there is, as we
pass from the early vertebrates down to man, a progress in the evolution
of the general associative process which practically equals animal
intellect, that this progress continues as we pass from the monkeys to
man. Such a progress is a real fact; it does exist as a possible _vera
causa_; it is thus at all events better than some imaginary cause of the
origin of human intellect, the very existence of which is in doubt. In a
similar manner we know that the neurones, which compose the brain and the
connections between which are the physiological parallels of the habits
that animals form, show, as we pass down through the vertebrate series,
an evolution along lines of increased delicacy and complexity. That an
animal associates a certain act with a certain felt situation means that
he forms or strengthens connections between certain cells. The increase
in number, delicacy and complexity of cell structures is thus the basis
for an increase in the number, delicacy and complexity of associations.
Now the evolution noted in cell structures affects man as well as the
other vertebrates. He stands at the head of the scale in that respect as
well. May not this obvious supremacy in the animal type of intellect and
in the adaption of his brain to it be at the bottom of his supremacy in
being the sole possessor of reasoning?

This question becomes more pressing if we realize that we must have some
sort of brain correlate for ideational life and reasoning. Some sort of
difference in processes in the brain must be at the basis of the mental
differences between man and the lower animals, we should all admit. And
it would seem wise to look for that difference amongst differences which
really do or at least may exist. Now the most likely brain difference
between man and the lower animals for our purpose, to my mind indeed the
only likely one, is just this difference in the fineness of organization
of the cell structures. If we could show with any degree of probability
how it might account for the presence of ideas and of reasoning, we
should at least have the satisfaction of dealing with a cause actually
known to exist.

The next important fact is that the intellect of the infant six months
to a year old is of the animal sort, that ideational and reasoning
life are not present in his case, that the only obvious intellectual
difference between him and a monkey is in the quantity and quality of
the associations formed. In the evolution of the infant’s mind to its
adult condition we have the actual transition within an individual from
the animal to the human type of intellect. If we look at the infant and
ask what is in him to make in the future a thinker and reasoner, we must
answer either by invoking some mysterious capacity, the presence of which
we cannot demonstrate, or by taking the difference we actually do find.
That is the difference in the quality and quantity of associations of the
animal sort. Even if we could never see how it came to cause the future
intellectual life, it would seem wiser to believe that it did than to
resort to faith in mysteries. Surely there is enough evidence to make it
worth while to ask our second question, “How might this difference cause
the life of ideas and reasoning?”

To answer this question fully would involve a most intricate treatment of
the whole intellectual life of man, a treatment which cannot be attempted
without reliance on technical terms and psychological formulas. A fairly
comprehensible account of the general features of such an answer can,
however, be given. The essential thing about the thinking of the animals
is that they feel things in gross. The kitten who learned to respond
differently to the signals, “I must feed those cats” and “I will not
feed them,” felt each signal as a vague total, including the tone, the
movements of my head, etc. It did not have an idea of the sound of _I_,
another of the sound of _must_, another of the sound _feed_, etc. It did
not turn the complex impression into a set of elements, but felt it, as I
have said, in gross. The dog that learned to get out of a box by pulling
a loop of wire did not feel the parts of the box separately, the bolt as
a definite circle of a certain size, did not feel his act as a sum of
certain particular movements. The monkey who learned to know the letter
K from the letter Y did not feel the separate lines of the letter, have
definite ideas of the parts. He just felt one way when he saw one total
impression and another way when he saw another.

Strictly human thinking, on the contrary, has as its essential
characteristic the breaking up of gross total situations into feelings
of particular facts. When in the presence of ten jumping tigers we not
only feel like running, but also feel the number of tigers, their color,
their size, etc. When, instead of merely associating some act with some
situation in the animal way, we think the situation out, we have a set
of particular feelings of its elements. In some cases, it is true, we
remain restricted to the animal sort of feelings. The sense impressions
of suffocation, of the feeling of a new style of clothes, of the pressure
of 10 feet of water above us, of malaise, of nausea and such like remain
for most of us vague total feelings to which we react and which we feel
most acutely but which do not take the form of definite ideas that we can
isolate or combine or compare. Such feelings we say are not parts of our
real intellectual life. They _are_ parts of our intellectual life if we
mean by it the mental life concerned in learning, but they are not if we
mean by it the life of reasoning.

Can we now see how the vague gross feelings of the animal sort might turn
into the well-defined particular ideas of the human sort, by the aid of a
multitude of delicate associations?

It seems to be a general law of mind that any mental element which occurs
with a number of different mental elements, appears, that is, in a number
of different combinations, tends to thereby acquire an independent life
of its own. We show children six lines, six dots, six peas, six pieces
of paper, etc., and thus create the definite feeling of sixness. Out of
the gross feelings of a certain number of lines, of dots, etc., we evolve
the definite elementary feeling of sixness by making the ‘six’ aspect of
the situations appear in a number of different connections. We learn to
feel whiteness as a definite idea by seeing white paper, white cloth,
white eggs, white plates, etc. We learn to feel the meaning of _but_ or
_in_ or _notwithstanding_ by feeling the meanings of many total phrases
containing each of them. Now in this general law by which different
associates for the same elementary process elevate it out of its position
as an undifferentiated fragment of a gross total feeling, we have, I
think, the manner in which the vague feelings of the nine-months-old
infant become the definite ideas of the five-year-old boy, the manner in
which in the race the animal mind has evolved into the human, and the
explanation of the service performed by the increase in the delicacy of
structure of the human brain and the consequent increase in the number of
associations.

The bottle to the six-months-old infant is a vague sense-impression which
the infant does not think about or indeed in the common meanings of the
words perceive or remember or imagine. Its presence does not arouse
ideas, but action. It is not to him a thing so big, or so shaped, or so
heavy, but is just a vaguely sizable thing to be reached for, grabbed and
sucked. Like the lower animals, with the exception that as he grows a
little older he reacts in very many more ways, the child feels things in
gross in a way to lead to direct reactions. Vague sense-impressions and
impulses make up his mental life. The bottle, which to a dog would be a
thing to smell at and paw, to a kitten a thing to smell at and perhaps
worry, is to the child a little later a thing to grab and suck and turn
over and drop and pick up and pull at and finger and rub against its toes
and so on. The sight of the bottle thus becomes associated with many
different reactions, and thus by our general law tends to gain a position
independent of any of them, to evolve from the condition of being a
portion of the cycles see-grab, see-drop, see-turn over, etc., to the
condition of being a definite idea.

The increased delicacy and complexity of the cell structures in the human
brain give the possibility of very small parts of the brain-processes
forming different connections, allow the brain to work in very great
detail, provide processes ready to be turned into definite ideas. The
great number of associations which the human being forms furnish the
means by which this last event is consummated. The infant’s vague
feelings of total situations are by virtue of the detailed working of
his brain all ready to split up into parts, and his general activity and
curiosity provide the multitude of different connections which allow them
to do so. The dog, on the other hand, has few or no ideas because his
brain acts in coarse fashion and because there are few connections with
each single process.

When once the mind begins to function by having definite ideas, all the
phenomena of reasoning soon appear. The transition from one idea to
another is the feeling of their relationship, of similarity or difference
or whatever it may be. As soon as we find any words or other symbols to
express such a feeling, or to express our idea of an action or condition,
we have explicit judgments. Observation of any child will show us that
the mind cannot rest in a condition where it has a large body of ideas
without comparing them and thinking about them. The ideas carry within
them the forces that make abstractions, feelings of similarity, judgments
and other characteristics of reasoning.

In children two and three years of age we find all these elements of
reasoning present and functioning. The product of children’s reasoning
is often irrational, but the processes are all there. The following
instances from a collection of children’s sayings by Mr. H. W. Brown show
children making inductions and deductions after the same general fashion
as adults:—

(2 yrs.) T. pulled the hairs on his father’s wrist. Father.
“Don’t, T., you hurt papa!” T. “It didn’t hurt grandpa.”

(2 yrs. 5 mos.) M. said, “Gracie can’t walk, she wears little
bits of shoes; if she had mine, she could walk. When I get some
new ones, I’m going to give her these, so she can walk.”

(2 yrs. 9 mos.) He usually has a nap in the forenoon, but
Friday he did not seem sleepy, so his mother did not put him
to bed. Before long he began to say, “Bolly’s sleepy; mamma
put him in the crib!” This he said very pleasantly at first;
but, as she paid no attention to him, he said, “Bolly cry, then
mamma will.” And he sat down on the floor and roared.

(3 yrs.) It was between five and six in the afternoon; the
mother was getting the baby asleep. J. had no one to play with.
He kept saying, “I wish R. would come home; mamma, put baby
to bed, so R. will come home.” I usually get home about six,
and as the baby is put to bed about half-past five, he had
associated the one with the other.

(3 yrs.) W. likes to play with oil paints. Two days ago my
father told W. he must not touch the paints any more, for he
was too small. This morning W. said, “When my papa is a very
old man, and when I am a big man and don’t need any papa, then
I can paint, can’t I, mamma?”

(3 yrs.) G.’s aunt gave him ten cents. G. went out, but soon
came back saying, “Mamma, we will be rich now.” “Why so, G.?”
“Because I planted my ten cents, and we will have lots of ten
cents growing.”

(3 yrs.) B. climbed up into a large express wagon, and would
not get out. I helped him out, and it was not a minute before
he was back in the wagon. I said, “B., how are you going to get
out of there now?” He replied, “I can stay here till it gets
little, and then I can get out my own self.”

(3 yrs.) F. is not allowed to go to the table to eat unless she
has her face and hands washed and her hair combed. The other
day she went to a lady visiting at her house and said, “Please
wash my face and hands and comb my hair; I am very hungry.”

(3 yrs.) If C. is told not to touch a certain thing, that it
will bite him, he always asks if it has a mouth. The other day
he was examining a plant, to see if it had a mouth. He was told
not to break it, and he said, “Oh, it won’t bite, because I
can’t find any mouth.”

Nowhere in the animal kingdom do we find the psychological elements of
reasoning save where there is a mental life made up of the definite
feelings which I have called ‘ideas,’ but they spring up like magic
as soon as we get in a child a body of such ideas. If we have traced
satisfactorily the evolution of a life of ideas from the animal life of
vague sense-impressions and impulses, we may be reasonably sure that no
difficulty awaits us in following the life of ideas in its course from
the chaotic dream of early childhood to the logical world-view of the
adult scientist.

In a very short time we have come a long way, from the simple learning of
the minnow or chick to the science and logic of man. The general frame
of mind which one acquires from the study of animal behavior and of the
mental development of young children makes our hypothesis seem vital and
probable. If the facts did eventually corroborate it, we should have an
eminently simple genesis of human faculty, for we could put together the
gist of our contention in a few words. We should say:—

“The function of intellect is to provide a means of modifying our
reactions to the circumstances of life, so that we may secure pleasure,
the symptom of welfare. Its general law is that when in a certain
situation an animal acts so that pleasure results, that act is selected
from all those performed and associated with that situation, so that,
when the situation recurs, the act will be more likely to follow than
it was before; that on the contrary the acts which, when performed in a
certain situation, have brought discomfort, tend to be dissociated from
that situation. The intellectual evolution of the race consists in an
increase in the number, delicacy, complexity, permanence and speed of
formation of such associations. In man this increase reaches such a point
that an apparently new type of mind results, which conceals the real
continuity of the process. This mental evolution parallels the evolution
of the cell structures of the brain from few and simple and gross to many
and complex and delicate.”

Nowhere more truly than in his mental capacities is man a part of nature.
His instincts, that is, his inborn tendencies to feel and act in certain
ways, show throughout marks of kinship with the lower animals, especially
with our nearest relatives physically, the monkeys. His sense-powers
show no new creation. His intellect we have seen to be a simple though
extended variation from the general animal sort. This again is presaged
by the similar variation in the case of the monkeys. Amongst the minds of
animals that of man leads, not as a demigod from another planet, but as a
king from the same race.

FOOTNOTES

[1] ‘Animal Intelligence: An Experimental Study of the Associative
Processes in Animals’ (’98), ‘The Instinctive Reactions of Young Chicks’
(’99), ‘A Note on the Psychology of Fishes’ (’99), and ‘The Mental Life
of the Monkeys’ (’01). I have added a theoretical paper, ‘The Evolution
of the Human Intellect,’ which appeared in the _Popular Science Monthly_
in 1901, and which was a direct outgrowth of the experimental work. I am
indebted to the management of the _Psychological Review_, and that of the
_American Naturalist_ and _Popular Science Monthly_, for permission to
reprint the three shorter papers.

[2] Unless one assumes telepathic influences.

[3] Reason in Common Sense, p. 154 ff.

[4] This chapter originally appeared as Monograph Supplement No. 8 of the
Psychological Review.

[5] I do not mean that scientists have been too credulous with regard
to spiritualism, but am referring to the cases where ten or twenty
scientists have been sent to observe some trick-performance by a
spiritualistic ‘medium,’ and have all been absolutely confident that they
understood the secret of its performance, _each of them giving a totally
different explanation_.

[6] The phrase ‘practically utter hunger’ has given rise to
misunderstandings. I have been accused of experimenting with starving or
half-starved animals, with animals brought to a state of fear and panic
by hunger, and the like!

The desideratum is, of course, to have the motive as nearly as possible
of equal strength in each experiment with any one animal with any one
act. That is, the animal should be as hungry at the tenth or twentieth
trial as at the first. To attain this, the animal was given after each
‘success’ only a very small bit of food as a reward (say, for a young
cat, one quarter of a cubic centimeter of fish or meat) and tested not
too many times on any one day. ‘Utter hunger’ means that no diminution in
his appetite was noted and that at the close of the experiment for the
day he would still eat a hearty meal. After the experiments for the day
were done, the cats received abundant food to maintain health, growth and
spirits, but commonly somewhat less than they would of their own accord
have taken. No one of the many visitors to the room mentioned anything
extraordinary or distressful in the animals’ condition. There were no
signs of fear or panic.

Possibly I was wrong in choosing the term ‘utter hunger’ to denote the
hunger of an animal in good, but not pampered, condition and without food
for fourteen hours. It is not sure, however, that the term ‘utter hunger’
is inappropriate. The few reports made of experiments in going without
food seem to show that, in health, the feeling of hunger reaches its
maximum intensity very early. It is of course not at all the same thing
as the complex of discomforts produced by long-continued insufficiency of
food. Hunger is not at all a synonym for starvation.

[7] The experiments now to be described were for the most part made in
the Psychological Laboratory of Columbia University during the year
’97-’98, but a few of them were made in connection with a general
preliminary investigation of animal psychology undertaken at Harvard
University in the previous year.

[8] No. 7 hit the string in his general struggling, apparently utterly
without design. He did not realize that the door was open till, two
seconds after it had fallen, he happened to look that way.

[9] No. 6, in trying to crawl out at the top of the box, put its paw in
above the string. It fell down and thus pulled the string. It did not
claw at it, and it was 16 seconds before it noticed that the door was
open. In all the other times that it escaped the movement was made in the
course of promiscuous scrambling, never in anything like the same way
that No. 2 made it.

[10] No. 3 did not go out until 12 seconds had elapsed after it had
pulled the string.

[11] The back of the pen adjoined the elevator shaft, being separated
from it by a partition 33 inches high. No. 2 heard the elevator coming up
and put his paws up on the top of this partition so as to look over. In
so doing he knocked the fastening of the cord at that end and opened the
door. He did not turn to come out, and I shut the door again.

[12] FF was a box 40 × 21 × 24 inches, the door of which could be opened
by putting the paw out between the bars to its right and pulling a loop
which hung 16 inches above the floor, 4 inches out from the box and 6
inches to the right of the door.

[13] KKK was box K with both bolts removed. All that had to be done was
to poke the paw out at one side of the door and press down a little bar
of wood.

[14] The cats and chick were left in for two minutes at each trial, the
dogs for from one to one and a half minutes.

[15] One result of the application of experimental method to the study of
the intellect of animals was the distinction of learning by the selection
of impulses or acts from learning by the selection of ideas. The usual
method of learning in the case of animals other than man was shown by
the studies reprinted in this volume to be the direct selection, in a
certain situation, of a desirable response and its association with that
situation, not the indirect selection of such a response by the selection
of some _idea_ which then of itself produced the response. The animals
did not usually behave as if they _thought of_ getting freedom or food
in a certain way and were thereby moved to do so, but as if the stimulus
in question made immediate connection with the response itself or an
intimately associated impulse.

The experiments had in this respect both a negative or destructive and
a positive or constructive meaning. On the one hand, they showed that
animal learning was not homologous with human association of ideas; that
animal learning was not human learning _minus_ abstract and conceptual
thought, but was on a still ‘lower’ level. On the other hand, the first
positive evidence that animals could, under certain circumstances, learn,
as man so commonly does, by the indirect connection of a response with a
situation through some non-sensory relic or representative of the latter,
came from my experiments.

It was perhaps natural that the more exciting denial of habitual learning
by ideas should have attracted more attention than the somewhat tedious
experiments to prove that under certain conditions they could so learn.
At all events, a perverse tradition seems to have grown up to the effect
that I denied the possibility of animals having images or learning in any
case by representative thinking.

There is some excuse for this tradition in the fact that whereas the
proof that the habitual learning of these dogs and cats did not require
‘ideas’ is clear and emphatic, my evidence that certain features of their
behavior _did_ require ‘ideas’ is complicated and imperfect.

The fact seems to be that a ‘free idea’ comes in the animals or in
man only as a result of a somewhat elaborate process of analysis or
extraction from a gross total sensory process. The primary level or grade
of experience, common to animals and little babies, comprises states
of mind such as an adult man gets if lost in anger, fear, suffocation,
dyspepsia, looking at a panorama of unknown objects with head upside
down, smelling the mixture of odors of a soap factory, driving a golf
ball, dashing to the net in a game of tennis, warding off a blow, or
swimming under water. For a man to get a distinct controllable percept of
approaching asthma, of a carpet loom seen upside down, or of a successful
‘carry through,’ or ‘smash’ or ‘lob,’ so that one knows just what one is
experiencing or doing, and can recall just what one experienced or did,
requires further experience of the element in question—contemplation of
it in isolation or dealings with it in many varied connections. So for
a cat to get a distinct controllable percept of a loop, or of its own
clawing or nosing or pulling, it must have the capacity to analyze such
elements out of the total gross complexes in which they inhere, and also
certain means or stimuli to such analysis.

This capacity or tendency the cats and dogs do, in my opinion, possess,
though in a far less degree than the average child. They also suffer from
lack of stimuli to the exercise of the capacity. Their confinement, for
the most part, to the direct sensory experience of things and acts, is
due in part to the weakness of the capacity or tendency of their neurones
to act in great detail, and in part to the lack of such stimuli as visual
exploration of things in detail, manual manipulation of the same thing
in many ways, and the identification of elements of objects and acts by
language. They get few free ideas because they are less ready than man to
get them under the same conditions and because their instinctive behavior
and social environment offer conditions that are less favorable. The task
of getting an animal to have some free ideational representative of a red
loop or of pushing up a button with the nose may be compared with that
of getting a very stupid boy to have a free ideational representative of
acceleration, or of the act of sounding _th_. The difference between them
and man which is so emphasized in the text, though real and of enormous
practical importance, is thus not at all a mysterious gap or trackless
desert. We can see our way from animal to human learning.

[16] A man may learn to swim from the general feeling, “I want to be
able to swim.” While learning, he may think of this desire, of the
difficulties of the motion, of the instruction given him, or of anything
which may turn up in his mind. This is all extraneous and is not
concerned in the acquisition of the association. Nothing like it, of
course, goes on in the animal’s mind. Imagine a man thrown into the water
repeatedly, and gradually floundering to the shore in better and better
style until finally, when thrown in, he swims off perfectly, and deprive
the man of all extraneous feelings, and you have an approximate homologue
of the process in animals. He feels discomfort, certain impulses to
flounder around, some of which are the right ones to move his body to
the shore. The pleasure which follows stamps in these, and gradually the
proper movements are made immediately on feeling the sense-impression of
surrounding water.

[17] See 10 in A, 3 in A, 10 in D; 10 in C, 4 in C, 3 in C; 6, 2, 5, 4 in
E; 4 in F; 10 in H, 3 in H; 3, 4, 5, in I; 4 in G, 3 in G; 3 in K; 10 in
L; dog 1 in N and CC; dog 1 in G and O.

[18] This chapter appeared originally in the _Psychological Review_, Vol.
VI, No. 3.

[19] This double rating is necessary because of the fact that the chick
often gives several distinct pecks in a single reaction. The ‘times
reacted to’ mean the number of different times that the chicks noticed
the color.

[20] The crude experiments reported in this and the preceding paragraphs
were not made to test the presence of color vision proper, that is,
of differentiation of two colors of the same brightness, but only to
ascertain how chicks reacted to ordinary colored objects. It was,
however, almost certain from the relative frequency of the reactions that
the intensity factor was not the cause of the response. For example, if
it had been, black on white and yellow on black should have been pecked
at oftener.

[21] This chapter appeared originally in the _American Naturalist_, Vol.
XXXIII, No. 396.

[22] This chapter appeared originally as Monograph Supplement No. 15 to
the _Psychological Review_.

[23] Pp. 20 to 155 of this volume.

[24] _American Journal of Psychology_, Vol. X, pp. 256-279; Vol. XI, pp.
80-100, 131-165; Vol. XII, pp. 206-239.

[25] Practically a memory trial of CC, done January 21, 1900.

[26] Did it by pulling door and thus shaking lever.

[27] Practically a memory trial of SS.

[28] Did it by pulling door and biting wire.

[29] This, I regret, was not done [E. L. T., 1911].

[30] The acts and the number of chances to see me do each and the results
were as follows; details can be found on the table on page 226. F =
failed after tuition.

No. 1.—MM 21 F
Theta 5 F
QQ 10 F
RR 4 F
W 9 did in .22
Delta 15 F
Epsilon 40 F
QQ (f) 15 F
QQ (c) 1 did in 2.20

No. 3.—Theta 25 did in 3.00.
QQ 40 F
Gamma 30 F
Epsilon 25 F
QQ (ff) 5 F
QQ (c) 20 F, did in 1.30, F, 5 F, 5 F
QQ (e) 5 F, did in 2.00

[31] He did push it once with his nose.

[32] I inadvertently pulled the nail out in one of five cases when I was
fingering it to see if attracting his attention to it would lead to the
act.

[33] Not significant. Due to inattention. Was temporary.

[34] Pulled wire and door.

[35] Pushed with head by chance.

[36] Reached in at 9:30 and took out the banana, which I replaced.

[37] Did by constant pulling at the door.

[38] Did touch nail four times.

[39] Did by pulling hard on wire (not loop); the loop got loose from nail.

[40] Did by pulling at the door till the bar was worked around.

[41] The ‘say,’ may be replaced by some bodily attitude, facial
expression, or other verbal formula that identifies the situation as one
to be responded to by speech.

[42] This would, of course, result from a well-known corollary of the
laws of habit.

[43] In _Essays Philosophical and Psychological in Honor of William
James_, pp. 591-599.

[44] Professor Smith’s own experiments illustrate this.

[45] Biological Lectures from the Marine Biological Laboratory of Woods
Holl, 1898, p. 323 ff.

[46] This chapter appeared originally in the _Popular Science Monthly_,
Nov., 1901.

INDEX

Abstraction, 120.
_See also_ Reasoning.

Action-system, importance of the study of the, 15 f.;
of monkeys, 190 f., 237.

Anecdotal school in animal psychology, 23 ff., 151 f.

Apparatus, descriptions of, 29 ff., 56 ff., 61 f., 169 f., 177 ff.,
196 ff.

Assimilation, 249 f.

Association, as a problem in animal psychology, 20 ff.;
by similarity, 116 ff.;
complexity of, 132 ff.;
conditions of, 43 ff.;
delicacy of, 128 ff., 195 ff.;
development of, in the animal kingdom, 285 ff.;
in cats, 38 ff.;
in chicks, 63 f.;
in dogs, 56 ff.;
in fishes, 169 ff.;
in man, 123 ff., 127, 285;
in monkeys, 182 ff., 194 f., 209 ff.;
in relation to attention, 44 ff.;
to individual differences, 52 ff.;
to inhibition, 142 ff.;
to instincts, 36 f., 142 ff.;
to previous experience, 48 ff.;
number of connections formed by, 135 ff.;
permanence of connections formed by, 138 ff., 194 f., 203 f.;
progress of, measurable by time-curves, 28, 40, 42;
the mental fact in, 98 ff.;
without ideas, 101 f., 127, 209 ff.
_See also_ Associations and Learning.

Associations, complexity, 132 ff.;
delicacy, 128 ff., 195 ff.;
number, 121, 135 ff.;
permanence, 138 ff., 194 f., 203 f.

Associative memory. _See_ Association.

Attention, 144 ff.;
and association, 44 ff.;
to imposed movements, 103 ff.

Behavior, acquired tendencies to, 244 ff. (_see also_ Association);
evolution of, 272 ff.;
general laws of, 241 ff.;
indefiniteness of the term, 5;
of cats, 35 ff., 88 f., and _passim_;
of chicks, 63 f., 138, 143 f., 156 ff., and _passim_;
of dogs, 59 ff., 92 ff.;
of fishes, 169 ff.;
of monkeys, 182 ff.;
original tendencies to, 242 f. (_see also_ Instincts);
predictability of, 241 f.;
proposed simplification of the laws of, 265 ff.;
_versus_ consciousness as an object of study, 1 ff.
_See also_ Association, Instincts, Learning, Memory, etc.

BOSWORTH, F. D., 240.

Cats, associative processes in, 35 ff.;
imitation in, 85 ff.;
the presence of ideas in, 100 ff.;
reasoning in, 67 ff.

Chicks, associative processes in, 61 ff.;
imitation in, 81 ff.;
instincts of, 156 ff.

Complexity, of associations, 132 ff.

Concepts, 116 ff.

Connection-systems, action of, in association, 246 ff., 266;
importance of the study of, 16 f.

Consciousness, amenability of, to scientific study, 7 ff.;
as pure experience, 13 f.;
as studied by the one who has or is it, 10 ff.;
of animals, 25 f., 67 ff., 98 ff., 123, 146 f., and _passim_;
social, 146 f.;
space-relations of, 14;
_versus_ behavior as an object of study, 1 ff.

Coördinations, of chicks, 160 ff.

DEAN, B., 161.

Delicacy of association, 128 ff., 195 ff.

DEWEY, J., 6.

Differences, between species of animals in the associative processes,
64 ff.

Discomfort, as an influence in learning, 245 ff.

Discrimination, in cats and dogs, 128 ff.;
in chicks, 156 ff.;
in monkeys, 195 ff.

Dogs, associative processes in, 56 ff.;
imitation in, 91 ff.;
the presence of ideas in, 115 f.;
reasoning in, 67 ff.

Education, applications of animal psychology in, 149 f.

Effect, the law of, 244 f., 266 ff.

Emotional reactions of chicks, 162 ff.

Evolution, of behavior, 272 ff.;
of human intellect, 282 ff.;
of ideas, 289 ff.

Exercise, the law of, 244 f.

Experience, the influence of previous, 48 ff.

Experiments, need of, in animal psychology, 26;
with cats, 35 ff., 85 ff., 103 ff., 111 f., 114 f., 129 ff., 138 f.;
with chicks, 61 ff., 81 ff., 132, 136, 143 f., 156 ff.;
with dogs, 56 ff., 91 ff., 103 ff., 115 f.;
with fishes, 169 ff.;
with monkeys, 176-235, _passim_.

Fears, of chicks, 162 ff.

Fishes, experiments with, 169 ff.

GALTON, F., 3.

Habit. _See_ Association.

HALL, G. S., 3.

Human. _See_ Man.

Hunger, effect of, on animal learning, 27 f.

HUNT, H. E., 163.

Ideas, development of, 121 f., 289 ff.;
existence of, as adjuncts in animal learning, 108 ff., 189 ff., 206
ff., 222 ff.;
impotence of, to create connections, 257 ff.

Ideo-motor action, 257 ff.

Images, 108 f. _See also_ Ideas.

Imitation, analysis of the supposed effects of, 251 ff.;
in cats, 85 ff.;
in chicks, 81 ff.;
in dogs, 91 ff.;
in general, 76 ff., 94 ff.;
in monkeys, 96, 211 ff., 219 ff.;
in speech, 253 ff.

Impulses, as features of the associative processes, 100 ff.;
defined, 37.

Incubation, the instinct of, 276 ff.

Individual differences in association, 52 ff.

Inhibition of instincts by association, 142 ff.

Instincts, as explanations of some cases of supposed imitation, 251;
inhibition of, 142 ff.;
of chicks, 156 ff.;
of incubation, 276 ff.;
of monkeys, 237;
the starting-point of animal learning, 36 f.

Intellect. _See_ Association, Ideas, Imitation, Memory, Reasoning,
etc.

Interaction, 147 f.

Introspection, the over-emphasis of, 3.

JAMES, W., 3, 120, 143, 286.

JENNINGS, H. S., 267, 268, 269, 270, 274, 279.

KLINE, L. W., 173.

Language, 253 ff.

Learning, evolution of, 278 ff.;
methods of, 174 f.
_See_ Association, Behavior, Ideas, Imitation, Reasoning.

LUBBOCK, J., 240.

Man, compared with lower animals in intellect, 123 ff., 239 f.;
mental evolution of, 282 ff.

Memory, 108 f., 138 ff., 203.
_See_ Association and Permanence of associations.

Methods in animal psychology, 22 ff.

MILLS, W., 191.

Monkeys, 172 ff.;
associative processes in, 182 ff.;
differences from lower mammals, 189 ff., 204 ff., 237 ff.;
general mental development of, 236 ff.;
imitation of man by, 211 ff.;
imitation of other monkeys by, 219 ff.;
possible mental degeneracy of, 151;
presence of ideas in, 189 ff., 206 ff., 222 ff.;
reasoning in, 184 ff.

MORGAN, C. L., 3, 80, 99 f., 101, 119, 120, 125 f., 146, 147, 162,
165 f.

Motives, used in the experiments, 26 ff.;
defined, 38.

Number of associations, 135 ff.;
as a cause of the development of free ideas, 121 f.

PECKHAM, G. W. and E. G., 240.

Pecking, accuracy of, in chicks, 159 f.

Pedagogy, applications of animal psychology to, 149 f.

Permanence of associations, 138 ff., 203.

Predictability of behavior, 241 f.

Primates. _See_ Monkeys.

Reasoning, 118 f.;
and free ideas, 291 ff.;
as a consequence of the laws of exercise and effect, 263 ff.;
in cats and dogs, 67 ff.;
in monkeys, 184 ff.

Recepts, 120.

Resolution, Jennings’ law of, 267 ff.

Responses to situations as the general form of behavior, 242 ff., 283
f.

ROMANES, G. J., 68 f., 70, 80.

SANTAYANA, G., 6, 18 f.

Satisfaction, the influence of, in learning, 147 f., 244 f.;
the nature of, 245 f.

Situation and response as the general form of behavior, 242 ff., 283
ff.

SMALL, W. S., 173.

SMITH, S., 269 f., 280.

Social consciousness of animals, 146 f.

SPALDING, D. A., 162, 163, 165.

STOUT, G. F., 3.

Swimming, by chicks, 161 f.

Time of achievement as a measure of the closeness of association,
28, 40, 42, 54.

Time-curves, 38 ff., 57 ff., 65, 185 f.;
as evidence against the existence of reasoning, 73 f.

TITCHENER, E. B., 2.

Vigor, as a factor in learning, 46.

WHITMAN, C. O., 275 ff.

YERKES, R. M., 240.

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The Animal Behavior Series

Under the General Editorship of ROBERT M. YERKES, Ph.D., Instructor in
Comparative Philosophy, Harvard University

The aim of the Series is to present a number of small volumes which taken
together shall form a comprehensive introduction to Comparative Psychology

_NOW READY_

The Dancing Mouse

By ROBERT M. YERKES, Ph.D.

_Cloth, 12mo, xxi + 290 pages, illus., $1.25 net_

“Dr. Yerkes’ book is a most interesting example of modern laboratory
methods and can be read with profit by any one, on account of the
accurate methods of observation and careful deductive reasoning
which it shows. An elaborate, painstaking system of experiments was
carried on with over 400 mice, with the object of determining muscular
coördination, structural peculiarities, strength of the special sense
organs, habit formation, educability, and strength of memory of these
little animals. Some experiments were also undertaken along the line of
inherited peculiarities.... The work is really only a preliminary study,
but it will be read with much interest by all students of comparative
psychology.”—_Journal of American Medical Association._

The Animal Mind

By MARGARET FLOY WASHBURN, Ph.D., Professor of Philosophy, Vassar College

_Cloth, 12mo, 333 pages, $1.60 net_

“As the author points out, the title of this book might more
appropriately have been ‘The Animal Mind Deduced from Experimental
Evidence,’ for the facts here set forth are very largely the results
of the experimental method in comparative psychology. The mass of
experimental material that has been accumulated from the researches of
physiologists and psychologists is already great, but is also for the
most part inaccessible to the ordinary student, being widely scattered
and to a considerable extent published in the journals of specialists,
which the average college library does not contain. Hence the usefulness
of the present ... interesting work.”—_New York Sun._

The Series is Published by
THE MACMILLAN COMPANY
64-66 Fifth Avenue, New York

OTHER NATURE BOOKS

Four-Footed Americans _And their Kin_

By MABEL OSGOOD WRIGHT. Edited by FRANK M. CHAPMAN. Illustrated by ERNEST
SETON THOMPSON

_Cloth, 12mo, $1.50 net; School Library Edition, 50 cents net_

“It deserves commendation for its fascinating style, and for the fund of
information which it contains regarding the familiar and many unfamiliar
animals of this country. It is an ideal book for children, and doubtless
older folk will find in its pages much of interest.”—_The Dial._

“Books like this are cups of delight to wide-awake and inquisitive girls
and boys. Here is a gossipy history of American quadrupeds, bright,
entertaining, and thoroughly instructive. The text, by Mrs. Wright, has
all the fascination that distinguishes her other outdoor books.”—_The
Independent._

Citizen Bird

_Scenes from Bird Life in Plain English for a Beginner_

By MABEL O. WRIGHT and Dr. ELLIOTT COUES. Profusely Illustrated by LOUIS
AGASSIZ FUERTES

_Cloth, 12mo, $1.50 net; School Library Edition, 50 cents net_

“When two writers of marked ability in both literature and natural
history unite to produce a work giving scope to their special talents,
the public has reason to expect a masterpiece of its kind. In the
‘Citizen Bird,’ by Mabel O. Wright and Dr. Elliott Coues, this
expectation is realized—seldom is the plan of a book so admirably
conceived, and in every detail so excellently fulfilled.”—_The Dial._

“There is no other book in existence so well fitted for arousing
and directing the interest that all children feel toward the
birds.”—_Tribune_, Chicago.

Flowers and Ferns _In their Haunts_

By MABEL OSGOOD WRIGHT

_New Edition, cloth, 12mo, $2.00 net_

The subjects are treated in their relation to landscape—the whole bound
together with a thread of narrative. The book thus has the fascination
of romance, yet no better handbook could be found for the study of the
flowers in their natural surroundings. There are over 50 full-page plates
of the flowers where they live and grow, along the roadside, in wood or
by river. In addition to these plates, there are over 100 illustrations
in the text, made direct from photographs by the author and by J. H.
McFarland.

A Text-book on the Principles of Animal Histology

By ULRIC DAHLGREN, M.S., Assistant Professor of Biology in Princeton
University; and WILLIAM A. KEPNER, A.B., Adjunct Professor of Biology in
the University of Virginia

_Cloth, 515 pp., 8vo, $3.75 net_

“The name of the senior author alone leads us to expect much from this
volume, and the most careful scrutiny reveals almost no defects. It
easily takes first place among histologies, chiefly because of the
invaluable comparative element. With few exceptions, histologies,
intended as they have been primarily for the medical student,
have heretofore been based for the most part on the genus _Homo_.
Morphologists and anatomists will welcome a general histology which in
the widest sense holds to its title, treating its subject as a pure
science.... One can scarcely imagine a clearer or better arranged
text-book either for the general student or for the specialist in any of
the many related sciences. Since scientists in many fields often have
occasion to refer to or to verify some point in histology, the volume
will appeal to readers outside of the domain of histology proper.”—_New
York Evening Post._

“In marked contrast to practically all the text-books of histology in
the English language, which deal largely or exclusively with human
or mammalian structures, this new book discusses the tissues of all
classes of animals. It is therefore possible to treat the subject much
more broadly and satisfactorily than has hitherto been done.”—_American
Journal of Science._

“When one considers the narrow, technical training which students in
histology usually receive, whether they be medical students or not, one
cannot but wish that a course similar to that outlined in this book might
be given in every college and university.”—_Science._

A Synoptic Text-book of Zoölogy for Colleges and Schools

By ARTHUR WISSWALD WEYSSE, A.M., Ph.D. (Harvard), Instructor in Zoölogy
at the Massachusetts Institute of Technology, and Associate Professor of
Physiology at Boston University

_Cloth, 545 pp., 8vo, $2.25 net_

“To relieve the tenseness of such a study as zoölogy, the author
deals—whenever practicable—with some facts of everyday interest, such as
the transmission of malaria by mosquitoes, the division of labor among
ants and bees, the storing of food for the young, and several others
of this character. These are pleasant little oases in the wilderness
of rigidly scientific terms and facts. Not only is the author to be
congratulated on the perseverance which made the volume possible, but
also are the publishers for the mechanical part they have played. The
book is entirely up to the high standard of the house that publishes it.
The illustrative element is most meritorious.”—_Journal of Education._

“A work of great value ... addressed to college students who do not
necessarily intend to become specialists, but approach the subject with
trained minds and with some knowledge of cognate sciences. We begin,
if not literally at the beginning, yet with the protoplasmic cell, but
pass almost immediately to the description of the various animal types
in which classification in minute subdivisions is not attempted. A third
part deals with the general principles of zoölogy. The book has been
specially adapted for use in connection with laboratory and field work,
as well as for systematic study.”—_Churchman._

“The text is noteworthy for its simplicity and clearness, and the choice
of subject-matter has been made with care. Considerable attention has
been paid to the introduction of illustrative data which bear on general
biological problems or are of economic or sanitary importance. The
book is also free from the more technical terminology which only the
specialist needs. The arrangement of the subject-matter is excellent.
After laying down a few general principles, the various animal types are
dealt with in detail, and the theoretical phases and general problems are
discussed in the closing section. The book forms a clearly presented,
well-balanced, comprehensive, and accurate epitome of zoölogy.”—_The
Dial._

Experimental Zoölogy

By THOMAS HUNT MORGAN, Professor of Experimental Zoölogy, Columbia
University

_Cloth, 454 pp., 8vo, $2.75 net_

“The author long ago won his spurs in this field, through his unrivaled
researches in the phenomena of regeneration; and he has now proved
himself a master of compilation—selecting the most significant
experiments carried on in various countries, weighing them fairly, and
summing up with a conservatism which is perhaps the most valuable feature
of the book. The thoroughness and lucidity of the work make it serve
three distinct purposes: the intelligent layman without any previous
knowledge of the subject may read and appreciate any part of it; the
student of experimental zoölogy will find it a veritable vade mecum; and
the advanced scientist will be glad to refer to the generous summaries of
literature relating to each subject.”—_Nation._

“Professor Morgan has, however, done much sound and some brilliant work.
In his special field, the regrowth of amputated parts and the relation
of this property to the general theory of evolution, his experiments
have become classic, and he is himself one of the first authorities
in the world. His own eminence in the field, combined with a simple,
straightforward style, and a just and sympathetic appreciation of the
work of other men, even when their opinions are opposed to his own,
render him especially well fitted to sum up the general results of the
new science. This he has accomplished with marked success in the work
before us. He has succeeded in bringing together a large body of fact
without becoming dull; without being fatuously ‘popular,’ he has been
untechnical and clear.”—_Boston Transcript._

The Protozoa

By GARY N. CALKINS, Ph.D., Instructor in Zoölogy, Columbia University

_Cloth, 347 pp., 8vo, $3.00 net_

“The author has not aimed at putting forward an exhaustive, severely
scientific treatise upon the group in question. His work may be described
rather as a simple and intelligible introduction to the study of the
Protozoa and of the many fascinating biological problems connected with,
or illustrated by, this subdivision of the animal kingdom, in such a way
as to awaken the interest of the beginner, no less than to strengthen the
hands of the expert.”—_Nature._

Text-book of Palæontology

By KARL A. VON ZITTEL, Professor of Geology and Palæontology in the
University of Munich. Translated and edited by CHARLES R. EASTMAN, Ph.D.,
in charge of Vertebrate Palæontology in the Museum of Comparative Zoölogy
at Harvard College, Cambridge, Mass.

_Vol. I. Cloth, 670 pp., with 1476 woodcuts, 8vo, $7.50 net_
_Vol. II. Cloth, 283 pp., with 373 woodcuts, $3.00 net_

NOTE.—This English edition has been enlarged and revised by the author
and editor in collaboration with the following specialists: C. E.
Beecher, J. M. Clarke, W. H. Dall, G. J. Hinde, A. Hyatt, J. S. Kingsley,
H. A. Pilsbry, C. Schuchert, S. H. Scudder, W. P. Sladen, E. O. Ulrich,
C. Wachsmuth, A. S. Woodward, E. C. Case, J. B. Hatcher, H. F. Osborn, S.
W. Williston, F. A. Lucas.

A Text-book of General Bacteriology

By WILLIAM DODGE FROST, Ph.D., Associate Professor of Bacteriology in the
University of Wisconsin; and EUGENE FRANKLIN McCAMPBELL, Ph.D., Associate
Professor of Bacteriology in the Ohio State University

_Cloth, 340 pp., $1.60 net_

Comparative Anatomy of Vertebrates

Adapted from the German of DR. ROBERT WIEDERSHEIM, Professor of Anatomy,
and Director of the Institute of Human and Comparative Anatomy in the
University of Freiburg-in-Baden. By W. N. PARKER, Ph.D., Professor of
Zoölogy at the University College of South Wales and Monmouthshire in the
University of Wales

_Cloth, 576 pp., 8vo, $3.75 net_

Text-book of the Embryology of Man and Mammals

By DR. OSCAR HERTWIG, Professor extraordinarius of Anatomy and
Comparative Anatomy, Director of the II Anatomical Institute of the
University of Berlin. Translated from the Third German Edition by EDWARD
L. MARK, Ph.D., Hersey Professor of Anatomy in Harvard University

_Cloth, 670 pp., 8vo, $5.25 net_

PUBLISHED BY
THE MACMILLAN COMPANY
64-66 Fifth Avenue, New York

*** End of this LibraryBlog Digital Book "Animal intelligence: Experimental studies" ***

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