Exposure to Common Enemies can Increase Political Polarization: Evidence from a Cooperation Experiment with Automated Partisans

Longstanding theory indicates the threat of a common enemy can mitigate conflict between members of rival groups. We tested this hypothesis in a pre-registered experiment where 1,670 Republicans and Democrats in the United States were asked to complete a collaborative online task with an automated agent or “bot” that was labelled as a member of the opposing party. Prior to this task, we exposed respondents to primes about a) a common enemy (involving threats from Iran, China, and Russia); b) a patriotic event; or c) a neutral, apolitical prime. Though we observed no significant differences in the behavior of Democrats as a result of these primes, we found that Republicans—and particularly those with very strong conservative views—were significantly less likely to cooperate with Democrats when primed about a common enemy. We also observed lower rates of cooperation among Republicans who participated in our study during the 2020 Iran crisis, which occurred in the middle of our fieldwork. These findings indicate common enemies may not reduce inter-group conflict in highly polarized societies, and contribute to a growing number of studies that find evidence of asymmetric political polarization. We conclude by discussing the implications of these findings for research in social psychology, political conflict, and the rapidly expanding field of computational social science.