This chapter discusses state as clearly as possible the assumptions underlying each formulation and shows how it is used to generate predictions, and considers the implications of representative research that bears upon the formulation. It provides several representative studies designed to test one or another implication of dissonance theory, and assesses both the support these studies provide for the theory and the extent to which they are consistent with the hypothesis that subjects respond in a way that they believe is consistent with experimental “demands.” The chapter describes a few studies in which predictions based upon the two formulations differ and evaluate the relative support for each. Predictions based upon Bem’s formulation are identical to those based upon dissonance theory. A nonmotivational formulation of the effects of one’s behavior upon one’s beliefs and attitudes has been developed by Bem.