[Footnote 1: Watson: Behavior. H. S. Jennings: Behavior of the Lower Organisms.]
In the last few years, as a result of the observation of animals under laboratory conditions, there has been increasing evidence of a large number of specific tendencies to act in specific ways, in response to specific given stimuli. As no stimuli are ever quite alike, and no animal organism is ever in exactly the same physico-chemical condition at two different times, there are slight but negligible differences in response. Allowing for these, animals may be said to be equipped with a wide variety of tendencies to do precisely the same things under recurrent identical circumstances. The aim of the experimental psychologist is to discover just what actions occur when an animal is placed in any given circumstances, precisely as the chemist notes what reaction occurs when two chemicals are combined.
While experiments with the human infant are more difficult and rare (and while it is among infants alone among humans that original tendencies can be observed free from the modifications to which they are so soon subjected by training and environment) careful observers find in the human animal also a great number of these specific ways of acting. Just which of the large number of observed universal modes of behavior are original and unlearned, is a matter still in controversy among psychologists. There is practically complete agreement among them, however, with respect to such comparatively simple acts as grasping, reaching, putting things in the mouth, creeping, standing and walking, and the making of sounds more or less articulate. Most psychologists recognize even such highly complicated tendencies as man's restlessness in the absence of other people, his tendency to attract their attention when present, to be at once pitying and pugnacious, greedy and sympathetic, to take and to follow a lead.
In general, it may be said that man possesses not fewer instincts than animals, but more. His superiority consists in the fact that he has at once more tendencies to respond, and that in him these tendencies are more flexible and more susceptible of modification than those of animals. A chicken has at the start the advantage over the human; it can at first do more things and do them better. But it is the human baby who, though it cannot find food for itself at the start, can eventually be taught to distinguish between the nutritive values of food, secure food from remote sources, and make palatable food from materials which when raw are inedible.
An inventory and classification of man's original tendencies 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.