Persuasion Bias, Social Influence, and Uni-Dimensional Opinions

Persuasion Bias, Social Influence, and Uni-Dimensional Opinions

By Peter M. DeMarzo, Jeffrey Zwiebel, Dimitri Vayanos
2001Working Paper No. 1719

We propose a boundedly-rational model of opinion formation where agents are subject to the phenomenon of persuasion. We argue that persuasion whereby repeated exposure to an opinion has a cumulative effect on an agents beliefs is pervasive and closely related to the concept of social influence. In our model, agents communicate repeatedly according to a social network, but fail to adjust properly for possible repetitions of information they receive. We show that under general conditions, agents beliefs converge over time to a common belief, which is a weighted average of initial beliefs. Agents' weights can be characterized in several manners related to their network position, and can be interpreted as a measure of social influence. Furthermore, agents multi-dimensional beliefs generally converge to a single line prior to obtaining a consensus. Thus, long-run differences in opinion can be characterized by a uni-dimensional measure. We explore the implications of our model in several natural settings, including neighborhoods with bilateral communication, hierarchies, and political science.