Is a punisher always trustworthy? In-group punishment reduces trust

Third-party punishment (TPP) helps maintain social justice; the social preference model highlights desires to punish individuals who violate fairness and group norms. Third-party punishment affects bystanders' trust in punishers, but the effects of group factors are currently unknown. The current study assessed how the group condition between the punished and bystanders influences how third-party punishment affects bystander trust, using third-party punishment and trust game paradigms. A pre-experiment (N = 63) showed that third-party punishment affected trust between participants and the punisher. Study 1 (N = 164) showed that TPP improved trust between participants and an out-group punisher, whereas trust decreased under an in-group condition. Study 2 (N = 128) showed that increased trust was the result of increased perceived integrity of an out-group punisher by bystanders. Decreased in-group trust was the result of decreased benevolence consciousness. Third-party punishment only enhanced bystanders' trust for an out-group punisher, while the in-group condition revealed the opposite result.