Animal intelligence: Experimental studies

by Edward L. Thorndike

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.