The power of allies: Infants' expectations of social obligations during intergroup conflict.

Abstract Many species of animals form social allegiances to enhance survival. Across disciplines, researchers have suggested that allegiances form to facilitate within group cooperation and defend each other against rival groups. Here, we explore humans' reasoning about social allegiances and obligations beginning in infancy, long before they have experience with intergroup conflict. In Experiments 1 and 2, we demonstrate that infants (17–19 months, and 9–13 months, respectively) expect a social ally to intervene and provide aid during an episode of intergroup conflict. Experiment 3 conceptually replicated the results of Experiments 1 and 2. Together, this set of experiments reveals that humans' understanding of social obligation and loyalty may be innate, and supported by infants' naive sociology.