Group Identity Modulates Inter-Brain Synchronization During Repeated Lottery Contest

Overbidding in Tullock (1980) lottery contests is a robust finding in laboratory experiments. There exists plenty of evidence that demonstrates the effect of group identity on human behavior. This presents a viable avenue for mitigating or resolving the issue of overbidding. However, the impact of group identity on inter-brain interactive mechanisms during lottery contests remains unclear. Utilizing an electroencephalography (EEG) hyperscanning technique, this study explores how group identity affects inter-brain synchronization and topological properties in pairs of individuals during a contest. Behavioral results indicated that individual investment was significantly increased when bidding with outgroup members. Analysis of inter-brain synchronization revealed a significant surge when bidding with ingroup members in contrast to outgroup. The graph analysis results demonstrated that the ingroup condition displayed a stronger level of integration (demonstrated by lower modularity) than the outgroup. To extend existing studies, we further conducted an extended experiment to explore whether enhancing group identity can contribute to the reduction of conflicts. Under the ingroup condition, the Mission treatment exhibited a significant reduction in both individual investment and inter-brain synchronization when compared to the NoMission treatment. The results suggest that the behavior of bidding can be impacted by group identity, and that the problem of ingroup conflict can be mitigated by enhancing group identity.