it to give microscopic details. Rough observations, however, it
gives with considerable certainty. Who can doubt, for example, that a
well-practised act goes on with very little consciousness, or that
inner, silent speech often accompanies thinking? And yet we have only
introspection to vouch for these facts.

Objective Observation

But to say, as used to be said, that psychology is purely an
introspective science, making use of no other sort of observation, is
absurd in the face of the facts.

{12}

We have animal psychology, where the observation is exclusively
objective. In objective observation, the observer watches something
else, and not himself. In animal psychology, the psychologist, as
observer, watches the animal.

The same is true of child psychology, at least for the first years of
childhood. You could not depend on the introspections of a baby, but
you can learn much by watching his behavior. Abnormal persons, also,
are not often reliable introspectionists, and the study of abnormal
psychology is mostly carried on by objective methods.

Now how is it with the normal adult human being, the standard subject
for psychology? Does he make all the observations on himself or may he
be objectively observed by the psychologist? The latter, certainly. In
fact, nearly all tests, such as those used in studying differential
psychology, are objective. That is to say that the person tested is
given a task to perform, and his performance is observed in one way or
another by the examiner. The examiner may observe the _time_ occupied
by the subject to complete the task, or the _quantity_ accomplished in
a fixed time; or he may measure the correctness and _excellence_ of
the work done, or the _difficulty_ of the task assigned. One test uses
one of these measures, and another uses another; but they are all
objective measures, not depending at all on the introspection of the
subject.

What is true of tests in differential psychology is true of the
majority of experiments in general psychology: the performer is one
person, the observer another, and the observation is objective in
character. Suppose, for example, you are investigating a memory
problem; your method may be to set your subject a lesson to memorize
under certain defined conditions, and see how quickly and well he
learns it; then you give him another, equally difficult lesson to be
learned under altered conditions, and observe whether he {13} does
better o