Theory Background Two distinct influence processes — informational and normative — are most widely accepted as causes of group polarization (Myers and Lamm 1976; Isenberg 1986; Brown 1986). The informational influence explanation, known as persuasive argu- ments theory, focuses on the role of novel arguments. In essence, group members who are on the same side of an issue will, in general, possess different arguments buttressing that side; discussion then exposes group members to new information supporting their initial inclination thereby shifting it further in the same direction. For the normative influence explanation, social comparison theory, a culturally salient norm acts so as to prejudice positions toward one pole. For example, a norm favoring risk-taking makes riskier positions more socially ideal than cautious ones. We address three key open questions in group polarization theory that limit its predictive ability in natural settings. The first, and most important, question in- volves how polarization mechanisms play out in conjunction with processes for resolv- ing disagreement. A strong reading of either persuasive arguments theory or social comparison theory implies that a shift toward the extreme should occur whenever group members are on the same side of an issue and, respectively, possess distinctive supporting information or operate under a salient biasing norm. However, group po- larization theory has never clearly explicated how the informational and normative mechanisms operate relative to stronger concurrent — and potentially countervailing — social influence processes, such as pressure toward consensus and majority influ- ence. The implicit assumption that, in the absence of the polarization preconditions, a group will typically converge to the mean of its initial opinion distribution has not been borne out experimentally (Davis 1996; Friedkin 1999; Ohtsubo, Masuchi, 5