Infants expect friends, but not rivals, to be happy for each other when they succeed

A friend telling you good news earns them a smile while witnessing a rival win an award may make you wrinkle your nose. Emotions arise not just from people's own circumstances, but also from the experiences of friends and rivals. Across three moderated, online looking time studies, we asked if human infants hold expectations about others' vicarious emotions and if they expect those emotions to be guided by social relationships. Ten- and 11-month-old infants (N = 154) expected an observer to be happy rather than sad when the observer watched a friend successfully jump over a wall; infants looked longer at the sad response compared to the happy response. In contrast, infants did not expect the observer to be happy when the friend failed, nor when a different, rival jumper succeeded; infants' looking times to the two emotion responses in these conditions were not reliably different. These results suggest that infants are able to integrate knowledge across social contexts to guide expectations about vicarious emotional responses. Here infants connected an understanding of agents' goals and their outcomes with knowledge of social relationships to infer an emotion response. Biased concern for friends but not adversaries is not just a descriptive feature of human relationships, but an expectation about the social world present from early in development. Further, the successful integration of these information types welcomes the possibility that infants can jointly reason about goals, emotions, and social relationships under an intuitive theory of psychology. RESEARCH HIGHLIGHTS: 11-month-old infants use knowledge of relationships to make inferences about others' vicarious emotions. In Experiment 1 infants expected an observer to respond happily to a friend's success but not their failure. Experiments 2 and 3 varied the relationship between the observer and actor and found that infants' expectation of vicarious happiness is strongest for positive relationships and absent for negative relationships. The results may reflect an intuitive psychology in which infants expect friends to adopt concern for one another's goals and to thus experience one another's successes as rewarding.