is made more difficult precisely because these are so easily modifiable and are, even in earliest childhood, seldom seen in their original and simple form.

At any given time a human being is being acted upon by a wide variety of competing and contemporaneous stimuli. In walking down a street with a friend, for example, one may be attracted by the array of bright colors, of flowers, jewelry and clothing in the shop windows, blink one's eyes in the glare of the sun, feel a satisfaction in the presence of other people and a loneliness for a particular friend, dodge before a passing automobile, be envious of its occupant, and smile benevolently at a passing child. It would be difficult in so complex and so characteristically familiar a situation to pick out completely and precisely the original human tendencies at work, and trace out all the modifications to which they have been subjected in the course of individual experience. For even single responses in the adult are not the same in quality or scope as they were to start with. Even the simplest stimuli of taste and of sound are different to the adult from what they are to the child. What for the adult is a printed page full of significance is for the baby a blur, or at most chaotic black marks on white paper.

But while it is difficult to disentangle out of even a simple, everyday occurrence the original unlearned human impulses at work, experimentation on both humans and animals seems clearly to establish that "in the same organism the same situation will always produce the same response." It also seems clear that in man these native unlearned responses to given stimuli are unusually numerous and unusually controllable. Upon the possibility of the ready modification of these original elements in man's behavior his whole education and social life depend.

Learning in animals and men. Men and animals are alike not only in that they have in common a large number of tendencies to respond in definite ways to definite stimuli, but that these responses may be modified, some strengthened through use, and others weakened or altogether discarded through disuse. In both also the survival and strengthening of some native tendencies, the weakening and even the complete elimination of others, depends primarily upon the satisfaction which flows from their practice.

It must be remembered that any situation, while it calls forth on the part of the organism a characteristic response, may also call out others, especially if the first response made fails to secure satisfaction, or if it places the animal in a positively annoying situation. There are certain situations—being fed when hungry, resting when weary, etc.—which are immediate and original satisfiers; there are others such as bitter tastes, being looked at with scorn by others, etc., which are natural annoyers. The first type the animal will try various means of attaining; the second, various means of avoiding. Through "trial and error," through going through every response it can make to a given situation, the animal or human hits upon some response which will secure for it satisfaction or rid it of a positive annoyance. Once this successful response is hit upon, it tends to be retained and becomes habitual in that situation, while other random responses are eliminated.

As will be pointed out in the following, man has developed in the process of reflection a much more effective and subtle mode of attaining desirable results, but a large part of human acquisition of skill, whether at the typewriter, the piano, the tennis court, or in dealing with other people, is still a matter of making every random response that the situation provokes until the appropriate and effective one is hit upon, and making this latter response more immediately upon repeated experiences in the same situation. Once this effective response becomes habitual it is just as automatic in character as if it had been made immediately the first time, and it is almost impossible without knowledge of the animal's or the human's earlier modes of response to detect the difference between an acquired response and one that is inborn.

This process of trial and error is perhaps best illustrated in the behavior of the lower animals where careful experiments have been conducted for the purpose of tracing the process of learning. In the classic cases reported by Thorndike and Watson, when chickens, rats, and cats were placed in situations where the first response failed to bring satisfaction, their behavior was in each case marked by the following features. At the first trial the animals in every case performed a wide variety of acts useless to secure the satisfaction they were instinctively seeking, whether it was food in a box, or freedom from confinement in a cage. Upon repeated trials the act appropriate to securing satisfaction was performed with increasing elimination of useless acts, and consequent decrease of the time required to perform the act requisite to secure food, or freedom, or both, as the case might be. One of Thorndike's famous cat experiments is best told in his own report:

If we take a box twenty by fifteen by twelve inches, replace its cover and front side by bars an inch apart, and make in this front side a door arranged so as to fall open when a wooden button inside is turned from a vertical to a horizontal position, we shall have means to observe such [learning by trial and error]. A kitten, three to six months old, if put in this box when hungry, a bit of fish being left outside, reacts as follows: It tries to squeeze through between the bars, claws at the bars, and at loose things in and out of the box, stretches its paws out between the bars, and bites at its confining walls. Some one of all these promiscuous clawings, squeezings, and bitings turns round the wooden button, and the kitten gains freedom and food. By repeating the experience again and again the animal gradually comes to omit all the useless clawings, and the like, and to manifest only the particular impulse (e.g., to claw hard at the top of the button with the paw or to push against one side of it with the nose) which has resulted successfully. It turns the button around without delay whenever put in the box. It has formed an association between the situation confined in a box with a certain appearance and the response of clawing at a certain part of that box in a certain definite way. Popularly speaking, it has learned to open a door by pressing a button. To the uninitiated observer the behavior of the six kittens that thus freed themselves from such a box would seem wonderful and quite unlike their ordinary accomplishments of finding their way to their food or beds.... A certain situation arouses, by virtue of accident or more often instinctive equipment, certain responses. One of these happens to be an act appropriate to secure freedom. It is stamped in in connection with that situation.[1]

[Footnote 1: Thorndike: Educational Psychology, Briefer Course. p. 129.]

Perhaps the most significant factor to be noted in this, and in similar cases, is that the successful response to a baffling situation is acquired, and that this acquisition remains a more or less permanent possession of the human or animal organism. Particularly important for the problem and practice of education is the mechanism by which these learned modes of behavior are acquired. For, to attain skill, knowledge, intellect, character, is to attain certain determinate habits of action, certain recurrent and stable ways of responding to a situation. The reason why the