Abstract:

Intergroup interaction is a primary type of social interaction, and plays an important role in human social development. Previous behavioral researches based on economic game tasks has demonstrated that the perception of partner’s group membership could modulate individuals’ mental processes and behavioral decision making when the participants play the game against an ingroup or outgroup member. However, it is still unclear how group membership influences the time course of recipient’s fairness considerations in the asset allocation task. In order to address this problem, we use the Minimal Group Paradigm to manipulate the ingroup-outgroup distinction between subjects and interactive partner, and integrate Ultimatum Game task and event-related potentials (ERPs) technique to explore how group membership affect the processing of fairness process and the time course of evaluation to allocation proposal. Brain potentials were recorded while 15 healthy adult subjects participated as recipients in the Ultimatum Game with alleged members of both an experimentally induced ingroup and outgroup, and subjects would receive either extremely unfair, moderately unfair, or fair offers from proposers. The behavioral data and ERP amplitudes (AN1 and MFN) associated with the three offers in both two interactions were analyzed. The behavioral data suggested that participants accepted more offers from ingroup partner than from outgroup partner, and the acceptance rates for extremely and moderately unfair offers were higher when interacting with ingroup partner than with outgroup partner whereas it did not show difference for fair offers irrespective of ingroup or outgroup partner making the offers. The ERP results indicated that AN1 and MFN were not only influenced by offers’ fairness but also modulated by the group membership. The AN1 was more negative for fair and moderately unfair offers compared to extremely unfair offers when playing against an outgroup member whereas it did not show differential responses to different offers from ingroup partner. The MFN and MFN effect (dMFN) was more negative for extremely unfair offers compared to fair offers in the intergroup interaction whereas it did not show differential responses to different offers in the outgroup interaction. These results indicated that group membership influenced the early stage of outcome evaluation under asset distribution game. In the intergroup interaction, both group membership and offers’ fairness influence the early attention detection and resource allocation, which induced the larger AN1 for fair and moderately unfair offers from outgroup partner. Moreover, the perception of belonging to a social group increased the fair anticipation to ingroup partner and decreased the fair anticipation to outgroup partner, which may induce the larger MFN difference for unfair offers. The present study first demonstrates that group membership and offers’ fairness can modulate the process of attention allocation and fairness considerations.

Key words: fairness considerations, group membership, Ultimatum Game, AN1, MFN