Bystander affiliation reduces the expression of anger in antagonists of interpersonal conflicts

Observations on human and nonhuman primates’ behaviour documented that bystanders play a key role in reducing the social tension following a conflict. While it is acknowledged that in nonhuman primates this decrease of tension is due to the calming effect exerted by bystanders on the stress of the antagonists, the emotional aspect of violence reduction remains largely unexplored in humans. In this study, we address this gap by investigating the effect of bystander affiliative intervention on stress-related behaviours indicating anxiety, anger and pain expressed by antagonists of conflicts. By conducting video analysis on interpersonal conflicts recorded by surveillance cameras in public spaces of Amsterdam, we found that antagonists displayed fewer anger-related behaviours after receiving non-physical affiliation, such as non-verbal interaction or proximity. Our findings suggest that bystanders adopt a safe option to regulate antagonists’ stress, showing a continuity in the conflict management strategies evolved in social animals.