We have seen that the smallest group – the dyad – presents nontrivial features of the influence process when both members of the dyad are influencing each other. The special case of a dyad with a source, who holds a fixed position on an issue, and a target, who may be influenced by the source, is a simple special case within a larger theoretical domain of possible influence networks that may occur in the dyad. When a group is enlarged by one member – the triad – the theoretical domain of possible influence networks also is enlarged. Now three persons may be mutually influencing one another on an issue, the interpersonal influences on each member may not be identical, and the susceptibilities of each member to attitude change also may not be identical. Festinger's (1954) theory of social comparison processes is a seminal attempt to develop a theory about the influence networks of groups that is applicable to the triad and larger influence systems.

Festinger's theory focused on the effects of the distribution of group members' initial attitudes, and members' positions in those distributions, upon the network of interpersonal influences among group members. The theory triggered a large and still unsettled literature. Despite the classic status of social comparison theory, most of the empirical work on the theory has not directly dealt with Festinger's key propositions concerning the effects of group members' initial positions on an issue (Goethals and Darley 1977; Latané 1966; Suls and Miller 1977; Suls, Martin, and Wheeler 2000; Suls and Wills 1991; Wood 1989).