Animal intelligence: Experimental studies

by Edward L. Thorndike

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.