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: