rough
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