This paper addresses the key challenge of how to promote intergroup cooperation. Using a lab-in-the-field experiment in Bougainville, Papua New Guinea, we study individuals' willingness to cooperate with another person in an incentivized social dilemma game. In a between-subjects design, we vary (i) whether individuals interact with a member of their own or another community, and (ii) whether individuals are observed by a key in-group member or not. We find that when individuals are not observed, they are less likely to cooperate with members of other communities. Yet, observation by an in-group member increases the share of people who cooperate with members of other communities from 17 percent to 70 percent, such that there is no in-group bias in cooperation when participants are observed. We relate the results to a shared understanding among the participants that intergroup cooperation is socially desirable. Our findings suggest that communities, organizations, and policymakers may leverage in-group observation to improve intergroup cooperation.
In many countries, partisans have become increasingly biased in how they evaluate others based on political affiliation. We suggest that this increase in affective polarization may in part be caused by changes in the global power distribution which caused many countries to experience a long period without external (military) threats. To study the importance of external threats, we conduct a priming experiment to examine how making Russia's full-scale invasion of Ukraine in 2022 salient causally influences affective polarization and collaboration in the U.S. We find that priming Americans with Russia's military aggression leads to a modest reduction in affective polarization and an increase in cooperativeness as measured by behavior in an incentivized coordination game. Surprisingly, the effect of making Russia's invasion salient does not depend on perceived cross-party disagreement about the conflict. These results suggest that researchers should also consider international relations to understand within-country polarization and willingness to collaborate.