The Animal Mind: A Textbook of Comparative Psychology

The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. THE title of this book might more appropriately, if not more concisely, have been “The Animal Mind as Deduced from Experimental Evidence.” For the facts set forth in the following pages are very largely the results of the experimental method in comparative psychology. Thus many aspects of the animal mind, to the investigation of which experiment either has not yet been applied or is perhaps not adapted, are left wholly unconsidered. This limitation of the scope of the book is a consequence of its aim to supply what I have felt to be a chief need of comparative psychology at the present time. Although the science is still in its formative stage, the mass of experimental material that has been accumulating from the researches of physiologists and psychologists is already great, and is also for the most part inaccessible to the ordinary student, being widely scattered and to a considerable extent published in journals which the average college library does not contain. While we have books on animal instincts and on the interpretation of animal behavior, we have no book which adequately presents the simple facts. '

Probably no bibliography seems to one who carefully examines it entirely consistent in what it includes and what it excludes. Certainly the one upon which this book is based contains inconsistencies. The design has been to exclude works bearing only upon general physiology, upon the morphology of the nervous system and sense organs, or upon the nature of animal instinct as such, and to include those which bear upon the topics mentioned in the chapter head-

ings. Within these limits, the collection of references upon Norwood Press J. 8. Cushing Co, — Berwick & Smith Co, Norwood, Mass., U.S.A, THE title of this book might more appropriately, if not more concisely, have been “The Animal Mind as Deduced from Experimental Evidence.” For the facts set forth in the following pages are very largely the results of the experimental method in comparative psychology. Thus many aspects of the animal mind, to the investigation of which experiment either has not yet been applied or is perhaps not adapted, are left wholly unconsidered. This limitation of the scope of the book is a consequence of its aim to supply what I have felt to be a chief need of comparative psychology at the present time. Although the science is still in its formative stage, the mass of experimental material that has been accumulating from the researches of physiologists and psychologists is already great, and is also for the most part inaccessible to the ordinary student, being widely scattered and to a considerable extent published in journals which the average college library does not contain. While we have books on animal instincts and on the interpretation of animal behavior, we have no book which adequately presents the simple facts.

Probably no bibliography seems to one who carefully examines it entirely consistent in what it includes and what it excludes. Certainly the one upon which this book is based contains inconsistencies. The design has been to exclude works bearing only upon general physiology, upon the morphology of the nervous system and sense organs, or upon the nature of animal instinct as such, and to include those which bear upon the topics mentioned in the chapter head-

ings. Within these limits, the collection of references upon no topic is as full as would be necessary for the bibliography of a special research upon that topic. Doubtless there are omissions for which no excuse can be found. In one or two cases, where the literature upon a single point is very large, as for example, in the case of the function of the semicircular canals, only a few of the more important references have been given.’ One further comment may be made. The book throughout deals with comparative rather than with genetic psychology.

I gratefully acknowledge help from a number of sources. To Professor Titchener I owe, not only my share of that genuine psychological spirit which he so successfully imparts to his pupils according to their ability, but various helpful criticisms upon the present work, about half of which he has read in manuscript. Dr. Yerkes has given me much invaluable aid in securing access to material, and has very kindly permitted me to see the proofs of his book on ‘The Dancing Mouse.” As editor of the series he has reviewed my manuscript to its great advantage. Professors Georges Bohn and George H. Parker have showed especial courtesy in making their work accessible tome. Professor Jennings has kindly allowed the use of a number of illustrations from his book on ‘‘ The Behavior of the Lower Organisms.”” My colleague Professor Aaron L. Treadwell has generously helped me in ways too numerous to specify. But perhaps my heaviest single obligation is to Professor I. Madison Bentley, who has read the manuscript of the entire book, and whose advice and criticism have been of the utmost

THe advance of comparative psychology during the past nine years has been remarkable. In preparing a second edition of this book I have tried to include every newly discovered .fact of the first importance, but the literature is now so extensive that in order to keep the bibliography within reasonable limits, I have had to exercise more selection than I did in preparing the bibliography for the first edition. For like reasons, the text of the book does not enter so fully into detail in describing the results of a particular investigation as was possible when the material at hand was so much less in amount.

More than half the book has been completely rewritten, including the chapters on Vision, on Spatially Determined Reactions, and on The Modification of Conscious Processes by Individual Experience. I hope that the edition represents an advance upon its predecessor, not only by including many newly ascertained facts, but also by presenting its subject matter in more logical form. Tue Dirricuttigs aND METHODS oF COMPARATIVE Psy- CHOLOGY et wee ae a. be Ce el 1. Difficulties. 2. Methods of Obtaining Facts: An- ecdote. 3. Methods of Obtaining Facts: Experiment. 4. Methods of Obtaining Facts: the Ideal Method. 5. Methods of Interpreting Facts.

6. Inferring Mind from Behavior. 7. Inferring Mind from Structure. 8. The Structure and Behavior of Amceba. 9. The Mind of Ameeba, dence of Discrimination. 12. Behavior as Evidence of Discrimination. 13. Evidence from Structure and Behavior Combined. 14. Evidence for Discrimination of Certain “Lower” Sensation Classes. , Chemical Sense in Mollusks. 20. The Chemical Sense in Echinoderms. 21. The Chemical Sense in Crustacea. 22. The Chemical Sense in Arachnida. 23. The Chemical Sense in Insects. 24. How Ants Find Food. 25. The Use of Smell in Path Finding by Ants. 26. How Ants “Recognize” Nest Mates. 27. How Bees Are Attracted to Flowers. 28. How Bees Find the Hive. 29. How Bees “Recognize” Nest Mates. 30. The Chemical Sense in Vertebrates. :

«<3 31. Hearing in Lower Invertebrates. 32. Hearing in Crustacea. 33. Hearing in Spiders. 34. Hearing in In- © g8. Change of Light Intensity as a Stimulus. 939. The Continuous Action of Light: Photokinesis. C40. The Problem of Visual Qualities: Invertebrates. 41. The Problem of Visual Qualities: Amphioxus and Fish. 42. The Problem of Visual Qualities : Reptiles and Amphibia. 43. The Problem of Visual Qualities: Birds. 44. The Problem of Visual Qualities: Mammals. ;

SPATIALLY DETERMINED REACTIONS AND SPACE PERCEPTION . 172-214 45. Classes of Spatially Determined Reactions. 46. Class I: Reactions to a Single Localized Stimulus. 47. Class II: Orienting Reactions: Possible Modes of Producing Them. 48. Orientation to Gravity: Protozoa#i 49. Orientation to Gravity: Ccelenterates. 50. Orientation to Gravity: Planarians. 51. Orientation to Gravity: An- nelids. 52. Orientation to Gravity: Mollusks. 53. Orientation to Gravity: Echinoderms. 54. Orientation to

Gravity: Crustacea. 55. Orientation to Gravity: Spiders and Insects. 56. Orientation to Gravity: Vertebrates. 57. The Psychic Aspect of Orientation to Gravity. 58. Orientation to Light. 59. Influences Affecting the Sense of Light Orientations. 60. The Psychic Aspect of Orientation to Light. 61. Mutual Influence of Light and Gravity Orientations. 62. Orientation to Other Forces. SPATIALLY DETERMINED REACTIONS AND SPACE PERCEPTION . 215-244 THE MoptFicaTion oF Conscious Processes By INDIVIDUAL Modifications Due to ‘Essentially Te nar Physio- ‘ me States: (c) Heightened Reaction as the Result of Previous Stimulation. 72. Modification Due to Essentially Temporary Physiological States: (6) Cessation of Reaction to a Repeated Slight Stimulus. 73. Modifications Due to Relatively Permanent Effects of Stimuli. 44. Learning Involving the Dropping Out of Movements. 75. The Formation of Systems of Successive Movements.

THe MopiIFICATION OF CONSCIOUS PROCESSES BY INDIVIDUAL 76. The RCo. of Lanttnand, 77. The Memory Jdéa- 78. Conditions Favoring the Development of Memory Ideas. 2. Some Alleged Instances of Remarkable Mental Powers in Animals. 80. Certain Influences Affecting Learning. Some ASPECTS OF ATTENTION . 4 i r . z + 314-323 81. The Interference of Stimuli. 82. Methods of Securing Prepotency of Vitally Important Stimuli. 83. The Peculiar Characteristics of Attention as a Device to Secure Prepotency.

Tat the mind of each human being forms a region inaccessible to all save its possessor, is one of the commonplaces | of reflection. His neighbor’s knowledge of each person’s mind must always be indirect, a matter of inference. How wide of the truth this inference may be, even under the most favorable circumstances, is also an affair of everyday experience: each of us can judge his fellow-men only on the basis of his own thoughts and feelings in similar circumstances, and the individual peculiarities of different members of the human species are of necessity very imperfectly comprehended by others. The science of human psychology has to reckon with this unbridgeable gap between minds as

a study are not distorted by some personal twist or bias. For the danger of confusing individual peculiarities with general mental laws. In a psychological experiment, an unbiassed observer is asked to study his own experience under certain definite conditions, and to put it into words so that the ex- _ perimenter may know what the contents of another mind are like in the circumstances. Thus language is the essential apparatus in experimental psychology; language with all its defects, its ambiguity, its substitution of crystallized concepts for the protean flux of actually lived experience, its lack of terms to express those parts of experience which are of small practical importance in everyday life, but which may be of the highest importance to mental science. Outside of the psychological laboratory language is not always the best guide to the contents of other minds, because it is not always the expression of a genuine wish to communicate thought. “Actions speak louder than words,” the proverb says; but when words are backed by good faith they furnish by far the safest indication of the thought of others. Whether, however, our inferences are made on the basis of words or of actions, they are all necessarily made on the \~ hypothesis that human minds are built on the same pattern, that what a given word or action would mean for my mind, this it means also for my neighbor’s mind.

5 If this hypothesis be uncertain when applied to our fellow human beings, it fails us utterly when we turn to the lower animals. If my neighbor’s mind is a mystery to me, how great is the mystery which looks out of the eyes of a dog, and how insoluble the problem presented by the mind of an invertebrate animal, an ant or aspider! We know that such minds must differ from ours not only in certain individual peculiarities, but in ways at whose nature we can only guess. The nervous systems of many animals vary widely from our own. We have, perhaps, too little knowledge about the

functions of our own to conjecture with any certainty what difference this must make in the conscious life of such animals ; but when we find sense organs, such as the compound eyes of insects or crustaceans, constructed ona plan wholly diverse from that of ours; when we find organs apparently sensory in function, but so unlike our own that we cannot tell what purpose they serve, — we are baffled in our attempt to construct the mental life of the animals possessing them, for lack of power to supply the sensation elements of that life. “Tt is not,”’ said Locke, ‘‘in the power of the most exalted wit or enlarged understanding, by any quickness or variety of thought,to invent or frame one new simple idea in the mind”’ (418, Bk. II, ch. 2); we cannot imagine a color or a sound or a smell that we have never experienced ; how much less the sensations of a sense radically different from any that we possess! Again, a bodily structure entirely unlike our own must create a background of organic sensation which renders the whole mental life of an animal foreign and unfamiliar to us. We speak, for example, of an “angry” wasp. Anger, in our own experience, is largely composed of sensations of quickened heart beat, of altered breathing, of muscular tension, of increased blood pressure in the head and face. The circulation of a wasp is fundamentally different from that of any vertebrate. The wasp does not breathe through lungs, it wears its skeleton on the outside, and it has the muscles attached to the inside of the skeleton. What is anger like in the wasp’s consciousness? We can form no adequate idea of it.

To this fundamental difficulty of the dissimilarity between animal minds and ours is added, of course, the obstacle that animals have no language in which to describe their expe; —~ rience to us. Where this unlikeness is greatest, as in the case of invertebrate animals, language would be of little use since we could not interpret it from our experience; but the higher vertebrates could give us much insight into their minds if they could only speak: Weare, however, restricted to the inferences we can draw from movements and sounds that are made for the most part without the intention of communicating anything tous. One happy consequence of this fact, which-to a slight extent balances its disadvantages, is that we have not to contend with self-consciousness and posing, which often invalidate human reports of introspection. ;

From these general considerations we can understand something of the special difficulties that beset the path of the comparative psychologist, who desires to know the contents of minds below the human level. Knowledge regarding the animal mind, like knowledge of human minds other than our own, must come by way of inference from behavior. Two fundamental questions then confront the comparative psychologist. First, by what method shall he find out how an animal behaves? Second, how shall he interpret the conscious aspect of that behavior ?

The reading of such a book as Romanes’s ‘‘ Animal Intelligence,” or of the letters about animal behavior in the London Spectator, will reveal one method of gathering information about what animals do. This has been termed the Method of Anecdote. It consists essentially in taking the | report of another person regarding the action of an animal, observed most commonly by accident, and attracting attention because of its unusual character. In certain cases the observer while engaged in some other pursuit happens to notice the singular behavior of an animal, and at his leisure

writes out an account of it. In others, the animal is a pet, in whose high intellectual powers its master takes pride. It is safe to say that this method of collecting information always labors under at least one, and uae under ge of the following disadvantages : — . The observer is not scientifically trained to distinguish shit he sees from what he infers: 2. He is not intimately acquainted with the habits of the species to which the animal belongs. 3. He is not acquainted with the past experience of the. individual animal concerned. 4. He has a personal affection for the animal concerned, : and a desire to show its superior intelligence. 5. He has the desire, common to all humanity, to tell a -

good story * Some of these tendencies to error it is unnecessary to illus- “trate. A good example of the dangers of (2), lack of acquaintance with the habits of the species, is given by Mr. and Mrs. Peckham. They quote the following anecdote reported by no less eminent and trained an observer than Wundt. ‘I had made myself,” says that psychologist, “as a boy, a fly-trap like a pigeon cote. The flies were attracted by scattering sugar and caught as soon as they had entered the cage. Behind the trap was a second box separated from it by a sliding door, which could be opened or shut at pleasure. In this I had put a large garden spider. Cage and box were provided with glass windows on the top, so that I could quite well observe anything that was going on inside. ... When some flies had been caught, and the slide was drawn out, the spider of course rushed upon her prey and devoured them. ... - This went on for some time. The spider was sometimes let into the cage, sometimes confined to her own box. But

one day I made a notable discovery. During an absence the slide had been accidentally left open for some little while. When I came to shut it, I found that there was an unusual resistance. As I looked more closely, I found that the spider had drawn a large number of thick threads directly under the lifted door, and that these were preventing my closing it... .” ‘What was going on in the spider’s mind?” Wundt asks, and points out that it is unnecessary to assume that she understood and reasoned out the mechanical requirements of the situation. The whole matter can be explained, he thinks, ina simpler way. ‘‘I imagine that as the days went by there had been formed in the mind of the spider a determinate association on the one hand between free entry into the cage and the pleasurable feeling attending satisfaction of the nutritive impulse, and on the other between the closed slide and the unpleasant feeling of hunger and inhibited impulse. Now in her free life the spider had always employed her web in the service of the nutritive impulse. Associations had therefore grown up between the definite positions of her web and definite peculiarities of the objects to which it was attached, as well as changes which it produced in the positions of certain of these objects, — leaves, small twigs, etc. The impression of the falling slide, that is, called up by association the idea of other objects similarly moved which had been held in their places by threads properly spun; and finally there were connected with this association the other two of pleasure and raising, unpleasantness and closing, of the door” (797, pp. 351-352).

The Peckhams remark in criticism of this observation: “Had Wundt been familiar with the habits of spiders, he would have known that whenever they are confined they walk around and around the cage, leaving behind them lines of web. Of course many lines passed under his little sliding door, and when he came to close it there was a slight resistance. These are the facts. His inference that there was even a remotest intention on the part of his prisoner to hinder the movement of the door is entirely gratuitous. Even the simpler mental states that are supposed to have passed through the mind of the spider were the products of Wundt’s own imagination” (572, p. 230). The fact that the anecdote was a recollection of childhood, so that it would probably be impossible to bring any evidence from the character of the web or other circumstance against the suggestion of Mr. and Mrs. Peckham, is a further instance of the unscientific use of anecdotal testimony.

An illustration of the third objection mentioned above, the disadvantage of ignorance of the animal’s individual history, is furnished by Lloyd Morgan. In describing his futile efforts to teach a fox terrier the best way to pull a crooked stick through a fence, he says that the dog showed no sign “of perceiving that by pushing the stick and freeing the crook he could pull the stick through. Each time the crook caught he pulled with all his strength, seizing the stick now at the end, now in the middle, and now near the crook. At length he seized the crook itself and with a wrench broke it off. A man who was passing .. . said, ‘Clever dog that, sir; he knows where the hitch do lie.’ The remark was the characteristic outcome of two minutes’ chance observation” (507, pp. 142-143). How many anecdotes of animals are based on similar accidents?

It will be seen that in both the cases just criticised the error lies in the interpretation of the animal’s behavior. Indeed, a root ‘of evil in the method of anecdote consists in the fact that observation in this form is imperfectly divorced from interpretation. The maker of an anecdote is seldom content with merely telling one what the animal did and leaving future investigation and the comparative study of many facts to decide what the animal’s conscious experience in doing it was like. The point of the anecdote usually consists in showing that a human interpretation of the animal’s behavior is possible. Here is shown the desire to tell a good story, which we mentioned among the pitfalls of the anecdotal method; the wish to report something unusual, not to get a just conception of the normal behavior of an animal. As Thorndike*has forcibly put it: “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” (704, p. 4).

All this is not to deny that much of the testimony to be found in Romanes’s “‘Animal Intelligence” and Darwin’s “Descent of Man” is the trustworthy report of trained observers; but it is difficult to separate the grain from the chaff, and one feels toward many of the anecdotes the attitude of scepticism produced, for example, by this tale which an Australian lady reported to the Linnean Society. The burial of some deceased comrades was accomplished, she says, by a nest of “‘soldier ants” near Sydney, in the following fashion. ‘‘All fell into rank walking regularly and slowly two by two, until they arrived at the spot where lay the dead bodies. . . . Two of the ants advanced and took up the dead body of one of their comrades; then

two others, and so on until all were ready to march. First walked two ants bearing a body, then two without a burden; then two others with another dead ant, and so on, until the line was extended to about forty pairs, and the procession now moved slowly onward, followed by an irregular body of about two hundred ants. Occasionally the two laden ants stopped, and laying ddwn the dead ant, it was taken up by the two walking unburdened behind them, and thus, by occasionally relieving each other, they arrived at a sandy spot near the sea.” A separate grave was then dug for each dead ant. ‘‘Some six or seven of the ants had attempted to run off without performing their share of the task of digging; these were caught and brought back, when they were at once attacked by the body of ants and killed upon the spot. A single grave was quickly dug and they were all dropped into it.”” No funeral procession for them! Of this story Romanes says, “‘The observation seems to have been one about which there could scarcely have been a mistake” (641, p. 91). One is inclined to think it just possible that there was.

Diametrically opposed to the Method of Anecdote and its unscientific character is the Method of Experiment. An experiment, properly conducted, always implies that the conditions are controlled, or at least known; whereas ignorance of the conditions is, as we have seen, a common feature of anecdote. The experimenter is impartial; he has no desire to bring about any particular result. The teller of an anecdote wishes to prove animal intelligence. The experimenter is willing to report the facts precisely as he observes them, and is in no haste to make them prove

anything. The conduct of an experiment upon an animal will, of course, vary according to the problem to be solved. If the object is to test some innate reaction on the animal’s part, such as its ordinary responses to stimulation or its instincts, one need merely place the animal under favorable conditions for observation, make sure that it is not frightened or in an abnormal state, supply the appropriate stimulus unmixed with others, and watch the result. If it is desired to study the process by which an animal learns to adapt itself to a new situation, one must, of course, make sure in addition that the situation really is new to the animal, and yet that it makes sufficient appeal to some instinctive tendency to supply a motive for the learning process.