Animal intelligence: Experimental studies

by Edward L. Thorndike

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.