hat is the animal's sensation or state of mind at any time; to
get at that, you would need a trustworthy report from the animal
himself. Each individual must observe his own consciousness; no one
can do it from outside. The objection of the behaviorist to
"consciousness psychology" arises partly from distrust of this method
of inner observation, even on the part of a human observer.

Indeed, we can hardly define psychology without considering its
_methods of observation_, since evidently the method of observation
limits the facts observed and so determines the character of the
science. Psychology has two methods of observation.

When a person performs any act, there are, or may be, two sorts of
facts to be observed, the "objective" and the "subjective". The
objective facts consist of movements of the person's body or of any
part of it, secretions of his glands (as flow of saliva or sweat), and
external results produced by these bodily actions--results such as
objects moved, path and distance traversed, hits on a target, marks
made on paper, columns of figures added, vocal or other sounds
produced, etc., etc. Such objective facts can be observed by another
person.

The subjective facts can be observed only by the person performing the
act. While another person can observe, better indeed than he can
himself, the motion of his legs in walking, he alone can observe the
sensations in the joints and muscles produced by the leg movement. No
one else can observe his pleased or displeased state of mind, nor
whether he is thinking of his walking or of something quite different.
To be sure, his facial expression, which is an objective fact, may
give some clue to his thoughts and feelings, but "there's no art to
read the mind's construction {10} in the face", or at least no sure
art. One may feign sleep or absorption while really attending to what
is going on around. A child may wear an angelic expression while
meditating mischief. To get the subjective facts, we shall have to
enlist the person himself as our observer.

Introspection

This is observation by an individual of his own conscious action. It
is also called subjective observation. Notice that it is a form of
observation, and not speculation or reasoning from probabilities or
from past experience. It is a direct observation of fact.

One very simple instance of introspection is afforded by the study of
after-images. Look for an instant at the glowing electric bulb