A number of very general differences exist between the ap-
proach 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 di-
rected 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 disso-
nance 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 prob-
lem of (4) conformity and social influence. The research is best repre-
sented 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

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