Rhetorically-Induced Group Polarization in Small Opinion Networks

We present a novel explanation for the group polarization effect whereby discussion induces shifts toward the extreme. In our theory, rhetorically-induced asymmetry preferentially facilitates majority formation among extreme group members thereby skewing consensus outcomes further in the extreme direction. Additionally, heuristic issue substitution can shift the effective reference point for discussion from the policy reference, yielding differential polarization by policy side. Two mathematical models implementing the theory are introduced: a simple rhetorically-proximate majority model and the accept-shift-constrict model of opinion dynamics on networks which allows for the emergence of enduring majority positions. These models produce shifts toward the extreme without the typical modeling assumption of greater resistance to persuasion among extremists. Our online group discussion experiment manipulated policy side, disagreement level, and network structure. The results, which challenge existing polarization theories, are in qualitative and quantitative accord with our theory and models.