Introspection

Introspection is contemplation on one's self, as opposed to extrospection, the observation of things external to one's self.

Cognitive psychology accepts the use of the scientific method, but rejects introspection as a valid method of investigation. It should be noted that Herbert Simon and Allen Newell identified the 'thinking-aloud' protocol, in which investigators view a subject engaged in introspection, and who speaks his thoughts aloud, thus allowing study of his introspection.

It is related to the term reflection and used in a similar way by some people.

Introspection was a once acceptable means of explaining psychological phenomenon. Introspection was used by German physiologist Wilhelm Wundt in the experimental psychology laboratory he had founded in Leipzig in 1879. Wundt believed that by using introspection in his experiments he would gather information into how the subject's minds were working, thus he wanted to examine the mind into its basic elements. On the same note, Wundt did not invent this type of looking into an individual's mind through their experiences; it can be dated back to Socrates. The important distinction is that Wundt took this method into the experimental arena and thus into the newly formed psychological field.

Source: Schultz, D. P. & Schultz, S. E. (2004). A history of modern psychology (8th ed.). Belmont, CA: Wadsworth/Thomson Learning.