Modeling the Forming of Public Opinion: An approach from Sociophysics

Abstract

This paper reviews a sociophysics two-state model for opinion forming that has proven heuristic power. The dynamics are driven by repeated small-group discussions; within each group, a local majority rule is applied to update the opinions of agents. Iterating the dynamics leads towards one of two opposite attractors at which every agent shares the same opinion. The successful attractor is a function of the initial support with respect to a certain threshold, the value of which depends on the size distribution of the local update groups. While odd-sized groups yield a threshold at fifty percent, even-sized groups, which allow the inclusion of doubt in the case of an opinion tie, produce a threshold shift toward either one of the two attractors, giving rise to minority opinion spreading. In addition, agents can be heterogeneous in their cognitive nature, obeying different rules to update their opinion. While floater agents are open to changing their mind, contrarians chose to oppose whatever opinion was held by the majority of agents in their vicinity, and inflexibles never change their mind. Contrarians and inflexibles have drastic and counter-intuitive effects on the opinion dynamics. Beyond certain critical proportions, contrarians trigger an upside change of the dynamics, making it threshold-less with only one attractor at precisely 50/50 regardless of the initial conditions. Inflexibles produce the same threshold-less dynamics, except with an asymmetric single attractor that favors a specific opinion, even when they start with very low support. The results are used to shed new and unexpected light on controversial issues such as global warming.