Cognitive Consequences of Forced Compliance by Leon Festinger and James Carlsmith was published in the 'Journal of Abnormal and Social Psychology.' The premise for this classic piece of research was to test what happens to a person's private opinion when they are forced to do or say something contrary to that opinion. It was the first of numerous studies to corroborate the theory of 'cognitive dissonance.' See following link to read this psychology classic in full for free. Cognitive Dissonance