Ingroup Love Drives Ingroup Bias within Natural Groups

Humans often favor their own group members over others, a preference that drives discrimination and intergroup conflicts. Whether such ingroup bias is a result of elevated concerns for one's group members or diminished concerns for outgroup members remains an open question. We test this experimentally with natural groups in Ethiopia that have varying intergroup relations (neutral vs. enmity) and strengths of group identity (weak vs. strong). We find that ingroup bias manifests as concern toward ingroup but not outgroup members and that a strong group identity amplifies ingroup concerns, whereas enmity has no effect. Our results thus identify shared group identity as a primary driver of concerns for others.