Knowing what to think by knowing who you are: Self-categorization and the nature of norm formation, conformity and group polarization.

This study tested two theoretical approaches to social influence using three influence paradigms. First the authors demonstrate that, in M. Sherif's (1936) autokinetic effect paradigm, the impact of confederates on the formation of a norm decreases as their membership of a different category is made more salient to subjects. Second, in the S. Asch (1956) conformity paradigm, surveillance effectively exerts normative pressure if done by an in-group but not by an out-group. In-group influence decreases and out-group influence increases when subjects respond privately. Self-report data indicate that in-group confederates create more subjective uncertainty than out-group confederates and public responding seems to increase cohesiveness with in-group-but decrease it with out-group sources of influence. In the third experiment the authors use the group polarization paradigm to demonstrate that, where categorical differences between two subgroups within a discussion group