(Un)common knowledge: Children use social relationships to determine who knows what

Socially savvy individuals track what they know and what other people likely know, and they use this information to navigate the social world. We examine whether children expect people to have shared knowledge based on their social relationships (e.g., expecting friends to know each other's secrets, expecting members of the same cultural group to share cultural knowledge) and we compare children's reasoning about shared knowledge to their reasoning about common knowledge (e.g., the wrongness of moral violations). In three studies, we told 4- to 9-year-olds (N = 227) about what a child knew and asked who else knew the information: The child's friend (Studies 1-3), the child's schoolmate (Study 1), another child from the same national group (Study 2), or the child's sibling (Study 3). In all three studies, older children reliably used relationships to infer what other people knew. Moreover, with age, children increasingly considered both the type of knowledge and an individual's social relationships when reporting who knew what. The results provide support for a 'Selective Inferences' hypothesis and suggest that children's early attention to social relationships facilitates an understanding of how knowledge transfers - an otherwise challenging cognitive process.