A Price Paid for Our Internal Strife: Escalated Intragroup Aggression and the Evolution of Ingroup Derogation

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.

An ingroup disadvantage in recognizing micro-expressions

Micro-expression is a fleeting facial expression of emotion that usually occurs in high-stake situations and reveals the true emotion that a person tries to conceal. Due to its unique nature, recognizing micro-expression has great applications for fields like law enforcement, medical treatment, and national security. However, the psychological mechanism of micro-expression recognition is still poorly understood. In the present research, we sought to expand upon previous research to investigate whether the group membership of the expresser influences the recognition process of micro-expressions. By conducting two behavioral studies, we found that contrary to the widespread ingroup advantage found in macro-expression recognition, there was a robust ingroup disadvantage in micro-expression recognition instead. Specifically, in Study 1A and 1B, we found that participants were more accurate at recognizing the intense and subtle micro-expressions of their racial outgroups than those micro-expressions of their racial ingroups, and neither the training experience nor the duration of micro-expressions moderated this ingroup disadvantage. In Study 2A and 2B, we further found that mere social categorization alone was sufficient to elicit the ingroup disadvantage for the recognition of intense and subtle micro-expressions, and such an effect was also unaffected by the duration of micro-expressions. These results suggest that individuals spontaneously employ the social category information of others to recognize micro-expressions, and the ingroup disadvantage in micro-expression stems partly from motivated differential processing of ingroup micro-expressions.

Disease Threat and the Functional Flexibility of Ingroup Derogation

While the findings from previous studies directly relate the ingroup derogation phenomenon to the evolved response of the behavioral immune system, there are three major limitations in the previous studies on the functional flexibility of ingroup derogation. The present study further investigated the functional flexibility of ingroup derogation by conducting three behavioral experiments on Chinese participants. In Experiment 1, we tested whether exposing to situational disease primes leads to an exaggerated ingroup derogation attitude by adopting a more rigorous control. In Experiment 2, we manipulated the source of disease threats to test whether the ingroup derogation mechanism adjusts its response according to the specific perceived vulnerabilities to the disease threats posed by ingroup and outgroup members. In Experiment 3, we tested whether recent illness promotes the expression of ingroup derogation attitudes. Results of the three experiments consistently showed that, the Chinese participants adjusted their ingroup derogation attitudes according to the external environmental disease cues (Experiments 1 and 2) and the internal physiological disease cues (Experiment 3). The results also showed that the ingroup derogation mechanism was sensitive to the specific perceived vulnerabilities to the ingroup disease threat and the outgroup disease threat (Experiment 2). Taken together, these results support the evolutionary hypothesis of ingroup derogation and suggest that the ingroup derogation found in East Asian cultures could be accounted by a functionally flexible disease-avoidance mechanism.