Group environment promotes the third-party punishment for maintaining social fairness: evidence from ERPs and neural oscillations

Third-party punishment (TPP) has evolved as a vital mechanism for enforcing social fairness, to reduce tit-for-tat escalations among peers. Third parties intervene in conflicts between individuals both in private and in front of audiences and larger groups. To explore the influence of group environment on TPP and its neural mechanism and to investigate the moderating effect of gain and loss contexts on TPP, this study employed a modified third-party punishment task based on the dictator game (DG) and used the within-subject experimental design to collect the EEG data of 25 Chinese college students for analysis. Neural results showed that the group environment induced a larger P2 than the individual environment. In addition, when third parties observed dictators unfairly sharing losses with recipients, the presence of a group activated greater mid-frontal delta and theta band activation than environments where individuals acted alone. P2 can help to identify or reflect risk assessment to account for social and reputation assessments and future group benefits. Delta band activation is involved in the disgust response in moral decision-making, suggesting that the group environment affects the emotional factors involved in third-party punishment when viewing unfairly distributed losses. Mid-frontal theta band activation indicates altruistic motivation, and it is also activated more sharply in the loss context in the presence of a group, suggesting that there is a stronger neural signal to intervene when the group environment is potentially at issue. This study provides electrophysiological evidence from EEG of how group environments interact with norm violations to influence how individuals enact third-party punishment to maintain social fairness.