Extreme justifications fuel polarisation

How does polarisation — as measured by mistreatment of political rivals — spread? In an online experiment, participants choose between splitting financial resources equally or discriminating against a supporter of the opposing political party. We vary the information subjects receive about others’ choices and justifications for discrimination. Exposure to extreme justifications for discrimination increases discrimination — particularly in a polarized environment, when many others are already discriminating — and it leads participants to adopt more extreme justifications themselves. Our findings suggest a self-reinforcing dynamic that may fuel polarisation: Exposure to extreme statements increases polarisation and the prevalence of extreme reasoning.