Living in ancestrally diverse states of the United States is associated with greater vagal tone.

Historically, exposure to dissimilar others ("strangers") was a physiologically arousing event-resulting in avoidance, distrust, and even conflict. Despite this, contemporary migration patterns are increasing intergroup contact. What gives rise to an individual's ability to regulate their arousal such that social engagement with outgroup members is possible? We propose that cultural practices that evolve in ancestrally diverse, compared to ancestrally homogeneous, societies provide more opportunities for society members to engage in emotion regulation. This regulatory exercise, in turn, promotes higher vagal tone-a physiological indicator of one's ability to effectively manage arousal in social interaction. In a secondary analysis of data from the MIDUS 2 Biomarker Project, we find that the ancestral diversity of the states of the United States significantly predicts the average vagal tone of the state's citizens. The findings suggest that social context is associated with predictable and significant adaptations of human physiology over individual lifetimes.

Social Structure Predicts Eye Contact Tolerance in Nonhuman Primates: Evidence from a Crowd-Sourcing Approach.

In most primates, eye contact is an implicit signal of threat, and often connotes social status and imminent physical aggression. However, in humans and some of the gregarious nonhuman primates, eye contact is tolerated more and may be used to communicate other emotional and mental states. What accounts for the variation in this critical social cue across primate species? We crowd-sourced primatologists and found a strong linear relationship between eye contact tolerance and primate social structure such that eye contact tolerance increased as social structures become more egalitarian. In addition to constituting the first generalizable demonstration of this relationship, our findings serve to inform the related question of why eye contact is deferentially avoided in some human cultures, while eye contact is both frequent and even encouraged in others.

Third-party punishment following observed social rejection.

Humans routinely punish others for violating social norms. This behavior is referred to as third-party punishment. Much of the research on this topic has been done in the context of group cooperation and unjust economic interactions. However, little is known about punishment in response to other types of more personal transgressions. In the present study, we sought to determine whether adults would punish an individual after viewing them undeservingly reject a stranger. We experimentally demonstrate that after observing an individual socially reject an unknown victim, individuals will engage in third-party punishment. Individuals who reported feeling upset with the rejecter were most likely to punish, while feeling sorry for the victim was not predictive of punishment behavior. These findings highlight the motivational role of empathic anger in punishing social norm transgressors. Notably, individuals who reported having been bullied in their own pasts were the most likely to punish the rejecter. These results demonstrate how a history of being bullied may make one more attuned to the social rejection of others and in turn may make one more likely to take retributive action on behalf of another. (PsycInfo Database Record (c) 2020 APA, all rights reserved).