A group decision occurs when group members select or settle upon one option from a set of alternatives and collectively consider that option to be the choice of the group (Brandstatter, Davis, and Stocker-Kreichgauer 1982; Castellan 1993; Levine and Moreland 1990, 1998; Moscovici and Doise 1994; Witte and Davis 1996). Social influence network theory has an important bearing on how groups make decisions, because it presents an account of how interpersonal influences produce the agreements that are the foundation of many group decisions. In this chapter, we describe how our theory is related to several lines of formal work on group decision-making in which a decision scheme or normative procedure is invoked to reach a group decision.

We concentrate our analysis on social decision scheme theory, arguably the most prominent approach among psychologists to group decisions, and this theory's application to jury outcomes. The extant literature on social decision scheme theory indicates that groups behave as if different decision schemes are invoked to reach a collective decision, depending on the type of issue that is being dealt with. We show that a social influence network perspective provides a unifying formal framework. A single social process suffices to account for these issue-contingent results.

We then consider the relationship of social influence network theory and several formal normative models of group decision-making.