Full Idea
Experiments have shown (Nisbett and Wilson 1977) that people's introspective knowledge is a lot less reliable than they suppose. People are sensitive to but entirely unaware of many factors that influence their social behaviour.
Gist of Idea
Experiments prove that people are often unaware of their motives
Source
Georges Rey (Contemporary Philosophy of Mind [1997], 3.2.2)
Book Reference
Rey,Georges: 'Contemporary Philosophy of Mind' [Blackwell 1997], p.84
A Reaction
This type of observation rests on an overemphasis on the conscious mind. We are not conscious of liver events, or of deep buried brain events, both of which motivate us. We should only expect introspection to reveal what is fully conscious.