Pathogen-stress and terror-management theories predict that lethal epidemics heighten parochial cooperation. We test this prediction experimentally in two nationally representative U.S. samples surveyed before and at the onset of the COVID-19 pandemic. We compare trust and expected trustworthiness across the two waves in monetarily incentivized trust games involving non-Hispanic Whites, African Americans, and Hispanics. We find significant ingroup favoritism in both waves. However, the aggregate ingroup premium fell by about one-half between waves. This decline was concentrated among left-leaning and White respondents. Conversely, both African Americans and Hispanics displayed significant ingroup bias in both waves. While non-Hispanic Whites tended to reduce their ingroup bias in expected trust-worthiness, the opposite was found for African Americans. Respondents more exposed to COVID-19 displayed higher inter-group trust, altruism and expected trustworthiness than others. These results contradict the hypothesis that lethal epidemics intensify parochialism, also suggesting that the response may be diversified across groups.

