Negativity bias in the generalization of actions to group members by depressed adolescents

Social information processing in people with depression has been studied primarily in self-focused or individual contexts, leaving how adolescents with major depressive disorder (MDD) process actions in social group settings unclear. This study investigated whether depressed adolescents generalize group members’ actions with different valences. Using computer animations, we simulated social group interactions in which positive (helping) and negative (hindering) actions were observed. The participants then judged whether words describing helping, hindering, or neutral interactions were real words. Facilitation effects (faster responses for valenced vs. neutral words) were used to infer spontaneous generalization of group actions. With respect to hindering actions, adolescents with major depressive disorder (MDD) exhibited facilitation effects regardless of group membership ( N = 30), suggesting that they broadly generalized negative actions. In contrast, healthy controls exhibited no facilitation effect with respect to hindering actions. Notably, Children’s Depression Inventory scores were positively correlated with facilitation effects in adolescents with MDD. Adolescents with MDD also broadly generalized helping actions ( N = 30), exhibiting facilitation effects across group boundaries. However, healthy controls only exhibited a facilitation effect for members of the same group. Importantly, when information on group actions was not presented ( N = 31), facilitation effects in MDD adolescents disappeared for both helping and hindering actions. Adolescents with MDD spontaneously generalize both harmful and helpful actions to others regardless of group membership, whereas healthy controls demonstrate valence-dependent generalization—extending only helpful actions within groups. This suggests that adolescents with MDD exhibit negativity bias and broader generalization in terms of action expectations.