Considerable research has examined infants’ understanding and evaluations of social agents, but two questions remain unanswered: First, do infants organize observed social relations into larger structures, inferring the relationship between two social beings based on their relations to a third party?  Second, how do infants reason about a type of social relation prominent in all societies: the caregiving relation between parents and their babies?  In a series of experiments using animated events, we ask whether 15- to 18-month-old infants infer that two babies who were comforted by the same adult, or two adults who comforted the same baby, will affiliate with one another.  We find that infants make both of these inferences, but they make no comparable inferences when presented with the same visible events with voices that specify a peer context, in which one adult responds to another laughing adult.  Thus, infants are sensitive to at least one aspect of caregiving and organize relations between infants and adults into larger social structures.

In order to navigate the social world, children need to understand and make predictions about how people will interact with one another. Throughout most of human history, social groups have been prominently marked by kinship relations, but few experiments have examined children’s knowledge of and reasoning about kinship relations. In the current studies, we investigated how 3- to 5-year-old children understand kinship relations, compared to non-kin relations between friends, with questions such as, “Who has the same grandmother?” We also tested how children expect people to interact based on their relations to one another, with questions such as “Who do you think Cara would like to share her treat with?” Both in a storybook context and in a richer context presenting more compelling cues to kinship using face morphology, 3- and 4-year-old children failed to show either robust explicit conceptual distinctions between kin and friends, or expectations of behavior favoring kin over friends, even when asked about their own social partners. By 5 years, children’s understanding of these relations improved, and they showed some expectation that others will preferentially aid siblings over friends. Together, these findings suggest that explicit understanding of kinship develops slowly over the preschool years.