Opinion dynamics and wisdom under out-group discrimination

• A DeGroot-like opinion dynamics model with in- and out-group structure is proposed.
• Agents want to coordinate with their in-group & anti-coordinate with their out-group.
• Model predictions include persistent disagreement in connected societies.
• Necessary and sufficient conditions for bi-polarization are determined.
• We also determine opinion leadership and discuss (crowd) wisdom.

We study a DeGroot-like opinion dynamics model in which agents may oppose other agents. As an underlying motivation, in our setup, agents want to adjust their opinions to match those of the agents of their ‘in-group’ and, in addition, they want to adjust their opinions to match the ‘inverse’ of those of the agents of their ‘out-group’. Our paradigm can account for persistent disagreement in connected societies as well as bi- and multi-polarization. Outcomes depend upon network structure and the choice of deviation function modeling the mode of opposition between agents. For a particular choice of deviation function, which we call soft opposition, we derive necessary and sufficient conditions for long-run polarization. We also consider social influence (who are the opinion leaders in the network?) as well as the question of wisdom in our naïve learning paradigm, finding that wisdom is difficult to attain when there exist sufficiently strong negative relations between agents.1