Discussion We have presented experimental results that challenge standard theories of group polarization and have proposed an alternative theory. Our theory links RIA with the familiar social influence phenomena of majority influence and consensus pressure. The concavity of the rhetorical function compresses the rhetorical distance between group members with more extreme policies relative to more moderate ones. This distortion facilitates the emergence of extreme majorities that drive the ultimate group consensus yielding a shift toward the policy extreme relative to the initial policy mean — the definition of group polarization. Heuristic issue substitution can shift the reference point as well, with the rhetorical reference being the consequential divide for polarization. Both the RPM and ASC models qualitatively and quantitatively agree with our experimental results involving greater polarization for favorites than underdogs, as disagreement level increases, and for complete networks as compared with chains. RIA-based polarization can operate concurrently with the informational and nor- mative routes. Yet our theory’s ability to be implemented via formal models that can make predictions for specific opinion distributions speaks to its particular mer- its. In contrast, conventional theory always predicts polarization for groups with homogeneous leanings even if majority influence would predict depolarization. The RIA-based mechanism surmounts difficulties faced by attempts to account for group polarization through majority influence alone, such as its occurrence for symmetric opinion distributions (Myers and Lamm 1976:611-613). We grounded our discussion of the rhetorical function in the theory of decision making under risk and uncertainty. Its concavity even for a proper rhetorical issue suggests that policy experts, presumably less prone to heuristic substitution, will also 36