RESUMO
This chapter reviews research on the group identity explanation of social influence, grounded in self-categorization theory, and contrasts it with other group-based explanations, including normative influence, interdependence, and social network approaches, as well as approaches to persuasion and influence that background group (identity) processes. Although the review primarily discusses recent research, its focus also invites reappraisal of some classic research in order to address basic questions about the scope and power of the group identity explanation. The self-categorization explanation of influence grounded in group norms, moderated by group identification, is compared and contrasted to other normative explanations of influence, notably the concept of injunctive norms and the relation to moral conviction. A range of moderating factors relating to individual variation, features of the intragroup and intergroup context, and important contextual variables (i.e., anonymity versus visibility, isolation versus copresence) that are particularly relevant to online influence in the new media are also reviewed.