It is a natural assumption that animals are conscious, but after all you cannot directly observe their consciousness, and you cannot logically confute those philosophers [{9}] who have contended that the animal was an unconscious automaton. Still less can you be sure in detail what 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, and then turn your eyes upon a dark background, and observe whether the glowing filament appears there; this would be the "positive after-image". This simple type of introspection is used by physiology in its study of the senses, as well as by psychology; and it gives such precise and regular results that only the most confirmed behaviorists refuse to admit it as a good method of observation.
But psychology would like to make introspective observations on the more complex mental processes as well; and it must be admitted that here introspection becomes difficult. You cannot hope to make minute observations on any process that lasts over a very few seconds, for you must let the process run its natural course unimpeded by your efforts at observing it, and then turn your "mental eye" instantly back to observe it retrospectively before it disappears. As a matter of fact, a sensation or feeling or idea hangs on in consciousness for a few seconds, and can be observed in this retrospective way. There is no theoretical objection to this style of introspection, but it is practically difficult and [{11}] tricky. Try it on a column of figures: first add the column as usual, then immediately turn back and review exactly what went through your mind in the process of adding---what numbers you spoke internally, etc. Try again by introspecting the process of filling in the blanks in the sentence:
"Botany could not make use of introspection because ______ have probably no ________ processes."
At first, you may find it difficult to observe yourself in this way; for the natural tendency, when you are aiming at a certain result, is to reach the goal and then shift to something else, rather than to turn back and review the steps by which you reached the goal. But with practice, you acquire some skill in introspection.