pen the gate by lifting the latch; but it was found that
dogs and cats, and even monkeys, could not learn the trick in this
way. If, however, you placed a dog in a cage, the door of which could
be opened by lifting a latch, and motivated the dog strongly by having
him hungry and placing food just outside, then the dog went to work by
trial and error, and lifted the latch in the course of his varied
reactions; and if he were placed back in the cage time after time, his
unsuccessful reactions were gradually eliminated and the successful
reaction was firmly attached to the situation of being in that cage,
so that he would finally lift the latch without any hesitation.

The behavior of the animal does not look like reasoning. For one
thing, it is too impulsive and motor. The typical {464} attitudes of
the reasoner, whether "lost in thought" or "studying over things", do
not appear in the dog, or even in the monkey, though traces of them
may perhaps be seen in the chimpanzee and other manlike apes. Further,
the animal's learning curve fails to show sudden improvements such as
in human learning curves follow "seeing into" the problem. In short,
there is nothing to indicate that the animal recalls facts previously
observed or sees their bearing on the problem in hand. He works by
motor exploration, instead of mental. He does not search for
"considerations" that may furnish a clue.

The behavior of human beings, placed figuratively in a cage, sometimes
differs very little from that of an animal. Certainly it shows plenty
of trial and error and random motor exploration; and often the puzzle
is so blind that nothing but motor exploration will bring the
solution. What the human behavior does show that is mostly absent from
the animal is (1) attentive studying over the problem, scrutinizing it
on various sides, in the effort to find a clue; (2) thinking,
typically with closed eyes or abstracted gaze, in the effort to recall
something that may bear on the problem; and (3) sudden "insights" when
the present problem is seen in the light of past experience.

Though reason differs from animal trial and error in these respects,
it still is a tentative, try-and-try-again process. The right clue is
not necessarily hit upon at the first try; usually the reasoner finds
one clue after another, and follows each one up by recall, only to get
nowhere, till finally he notices a sign that recalls a pertinent
meaning. His exploration of the situa