CHAPTER VII. The Evolution of the Human Intellect[46]

THE EVOLUTION OF THE HUMAN INTELLECT

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

‘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.

Unless one assumes telepathic influences.

Reason in Common Sense, p. 154 ff.

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

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.

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.

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.

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.

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.

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

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.

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.

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.

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

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.

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.

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.

This chapter appeared originally in the Psychological Review, Vol. VI, No. 3.

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.

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.

This chapter appeared originally in the American Naturalist, Vol. XXXIII, No. 396.

This chapter appeared originally as Monograph Supplement No. 15 to the Psychological Review.

Pp. 20 to 155 of this volume.

American Journal of Psychology, Vol. X, pp. 256-279; Vol. XI, pp. 80-100, 131-165; Vol. XII, pp. 206-239.

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

Did it by pulling door and thus shaking lever.

Practically a memory trial of SS.

Did it by pulling door and biting wire.

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

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

He did push it once with his nose.

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.

Not significant. Due to inattention. Was temporary.

Pulled wire and door.

Pushed with head by chance.

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

Did by constant pulling at the door.

Did touch nail four times.

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

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

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.

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

In Essays Philosophical and Psychological in Honor of William James, pp. 591-599.

Professor Smith’s own experiments illustrate this.

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

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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