Modeling efforts in opinion dynamics have to a large extent ignored that opinion exchange
between individuals can also have an effect on how willing they are to express their
opinion publicly. Here, we introduce a model of public opinion expression. Two groups
of agents with different opinion on an issue interact with each other, changing the
willingness to express their opinion according to whether they perceive themselves
as part of the majority or minority opinion. We formulate the model as a multigroup
majority game and investigate the Nash equilibria. We also provide a dynamical systems
perspective: Using the reinforcement learning algorithm of Q-learning, we reduce the
N-agent system in a mean-field approach to two dimensions which represent the two
opinion groups. This two-dimensional system is analyzed in a comprehensive bifurcation
analysis of its parameters. The model identifies social-structural conditions for
public opinion predominance of different groups. Among other findings, we show under
which circumstances a minority can dominate public discourse.
