A number of very general differences exist between the approach to attitude change and social influence taken by dissonance theory and that taken by other theoretical approaches. The dissonance approach may be distinguished from the approach of, for example, the Yale program of research on communication and attitude change directed by Carl Hovland. The Yale program has been one of the major sources of research on the determinants of attitude change, and it is therefore instructive to use some central aspects of this work as a reference point for evaluating the distinctive contributions of dissonance theory. We shall discuss this under three headings: (1) research on communication discrepancy and attitude change, (2) research on improvisation and attitude change, and (3) self-esteem and attitude change. Another set of research issues has grown up around the problem of (4) conformity and social influence. The research is best represented by small group research on social influence and by some of Asch's research.
A good deal of experimental evidence exists which shows that the more extreme an attitude or opinion, the more difficult it will be to