A Bayesian model of group polarization

The group polarization hypothesis states that individual attitudes tend to become more extreme, “more polarized,” as a result of group discussion. The hypothesis was developed as a generalization of the well-known risky shift effect: the fact that individuals tend to make riskier decisions after group discussion than before group discussion. The group polarization hypothesis is supported by much experimental evidence. The principles of Bayesian decision theory are used to model how individual attitudes will change after group discussion. The model predicts the group polarization effect. Thus (1) it is shown that the group polarization effect can be viewed as arising from individual rationality, (2) a model of how much individual attitudes change after group discussion is derived.