Studies of social influence divide most readily between those that consider how the mere presence of other people influences one’s behaviour, and those that focus on situations where people actively try to influence one another. M. Deutsch and H. B. Gerard proposed that there were two elements explaining the Asch effect, which they termed informational and normative social influence. Leadership theorists have frequently attempted to identify particular patterns of leadership behaviour that are associated with successful team performance. In the early part of the twentieth century it was believed that such patterns, or leadership traits, were inborn qualities. The B. H. Raven and J. Z. Rubin typology of social power has proved rather attractive to researchers, who have sought to delineate how widely each of the bases of social influence is employed in different settings. The leader’s relation to the group must be thought of as a two-way rather than a one-way influence process.