关键词: 内群体排斥, 外群体排斥, 合作行为, 内群体偏爱

Abstract: Whether social exclusion reduces or enhances the cooperative behavior of outcasts remains controversial. Based on the social identity theory and the social categorization theory, numerous studies have shown that group identity (i.e., ingroup vs. outgroup) is one of the most prominent elicitors of interpersonal cooperation. Social exclusion from ingroup or outgroup members can pose different threats to individuals. Specifically, outgroup exclusion can strengthen individuals’ sense of ingroup identity and thus enhance cooperation with ingroup members. It can also activate individuals’ hostility to outgroup members and thus reduce cooperation with them. Meanwhile, ingroup exclusion might impair individuals’ ingroup expectations, reduce their identity with the ingroup and consequently encourage a shift toward cooperation with outgroup members. Alternatively, ingroup exclusion may serve as a reminder for outcasts to adhere to group norms. This study aims to explore the relationship between social exclusion and cooperative behavior among Chinese adults from an ingroup-outgroup perspective.
The Minimal Group Paradigm, developed by Henri Tajfel and his colleagues in 1971, was used to randomly assign participants to either the blue group or the yellow group. The Cyberball Game, developed by Kipling Williams and his colleagues in 2000, was used to establish conditions of exclusion or non-exclusion. The Public Goods Game, developed by Gerald Marwell and Roger Ames in 1981, was utilized to assess the level of cooperative behavior among ingroup and outgroup members. Study 1 involved 120 college students (N_female = 55, M_age = 20.86 ± 1.65 years) and focused on investigating the effect of social exclusion on individuals’ cooperative behavior with ingroup members compared to outgroup members. This study used a mixed experimental design with a 2 (condition: exclusion, non-exclusion) × 2 (cooperator identity: ingroup, outgroup) format. Study 2 further examined the effects of social exclusion from outgroup members (Study 2a) and from ingroup members (Study 2b) on individuals’ cooperative behavior with ingroup versus outgroup members. Study 2a included 113 college students (N_female = 56, M_age = 20.65 ± 1.74 years) and employed a mixed experimental design with a 2 (condition: social exclusion by outgroup, control) × 2 (cooperator identity: ingroup, outgroup) format. Study 2b included 133 college students (N_female = 64, M_age = 20.01 ± 1.60 years) and utilized a mixed experimental design with a 2 (condition: social exclusion by ingroup, control) × 2 (cooperator identity: ingroup, outgroup) format. All experiments were conducted using E-Prime.
The results indicated that there was no significant main effect of social exclusion on cooperative behavior toward individuals with no ingroup and outgroup identities. Instead, individuals who experienced social exclusion exhibited significantly more cooperative behavior toward ingroup members compared to those who were not excluded. Furthermore, individuals who were excluded by outgroup members (Study 2a) demonstrated significantly greater cooperative behavior with their ingroup members than those who were not excluded by outgroup members. However, ingroup exclusion did not significantly reduce individuals’ cooperation with ingroup members, nor did it significantly increase cooperation with outgroup members (Study 2b). This suggests that ingroup exclusion does not compel individuals to abandon their ingroup members in favor of establishing new cooperative relationships with outgroup members.
Based on ingroup and outgroup perspectives, this study provides preliminary insights into the different associations between social exclusion and cooperation. According to the ingroup favoritism hypothesis, individuals are more likely to cooperate with members of their ingroup. This study offers further evidence that social exclusion, particularly the exclusion of outgroup members, increases individuals' cooperation with ingroup members, thereby reinforcing the ingroup favoritism effect. However, individuals who are excluded by ingroup members still choose to cooperate with ingroup members rather than leaving the group to collaborate with outgroup members. This suggests that individuals experiencing social exclusion exhibit distinct patterns of cooperation with ingroup members compared to outgroup members, indicating that ingroup exclusion and outgroup exclusion have different effects on cooperation. This reveals a phenomenon referred to as the “ingroup-outgroup differential effect.”

Key words: ingroup exclusion, outgroup exclusion, cooperative behavior, ingroup favoritism