In this chapter, we analyze the process of interpersonal influence on attitudes in isolated dyads. Dyadic relationships are usually part of larger networks of interpersonal relationships. Although most relationships are not isolated, there are instances of dyads whose members are isolated on particular issues that do not involve the influences of other persons. Here, our theoretical focus is on the influence systems of such isolated dyads, the smallest groups in which interpersonal influence may occur.

Simmel (1950) argued that social processes in isolated dyads are qualitatively different from those in triads and larger groups. He suggested that the presence of a third party (e.g., a “tertius gaudens”) importantly modifies the interaction between two persons. His ideas are not rigorously described but they are, nonetheless, important in sensitizing us to the possibility that certain social processes may occur in isolated dyads that do not occur in embedded dyads. Other investigators also have suggested that dyads are different from larger groups, that they may not simply be a special case of a group with n persons, but entail distinctive mechanisms (Levine and Moreland 1990: 586). For instance, Levine and Moreland (1998: 417) write,