Ingroup favoritism on perceived risk of infectious diseases

Humans live in social groups; thus, infectious diseases may threaten human health and safety. Do individuals exhibit ingroup favoritism or ingroup devaluation when faced with varying risks of infectious diseases? We generated relatively realistic disease scenarios to examine this question. We reported the results from three experiments in which we tested individuals' perceived disease risk from ingroup and outgroup members under high- and low-risk conditions. Experiment 1 used a realistic influenza scenario, and Experiments 2 and 3 used a realistic scenario of exposure to coronavirus disease 2019 (COVID-19). All three experiments showed that perceived disease risk was significantly lower from ingroup members than from outgroup members and significantly lower in low-risk conditions than in high-risk conditions. Furthermore, the perceived disease risk was significantly lower from ingroup members than from outgroup members in high-risk conditions but did not significantly differ in low-risk conditions, as in Experiment 1's influenza scenario and Experiment 2's COVID-19 vaccination scenario. This suggests that ingroup favoritism is flexible. The results support ingroup favoritism and the functional flexibility principle in response to disease threats according to perceived disease risk.