Group bias under uncertain environment: A perspective of third-party punishment.

Third-party punishment (TPP) effectively promotes social cooperation and maintains social norms in which equity plays a decisive role. When third-party and players are affiliated with different groups, there are two distinct phenomena-in-group favoritism (IGF) and black sheep effect (BSE)-in a certain environment. Equity loses its function as a benchmark when the environment is uncertain (de Kwaadsteniet et al., 2013). Thus, we hypothesized that individuals have a stronger IGF because there is more room for interpretations of their behaviors when an uncertain environment results in ambiguous social norms. We utilized a common resource dilemma (CRD) to manipulate the environmental uncertainty by varying the range of the resource size: a certain environment is represented by a resource size of fixed tokens (i.e., 500 tokens) and an uncertain one is represented by that of 300 to 700 tokens. Additionally, group affiliation is manipulated by the alumni relation between the third-party and players. The present study revealed that the uncertain environment led to stricter costly punishment. The experiment confirms the IGF rather than the BSE. We found boundary conditions between IGF and out-group derogation (OGD). When the players' harvest was not obviously violated, the size of TPP for a control group without group affiliation manipulation anchored those of the in-group and OGD occurred. Opposite, when the harvest was obviously violated, the size of TPP for the control group anchored those of the out-group and IGF occurred. The gender of the third-party affects its decision to punish, with men anchoring the control group's punishment to the in-group and showing OGD, whereas women anchoring the control group's punishment to the out-group and showing IGF.