The foundations of reasoning about social hierarchy

Navigating the complexities of social relationships is a fundamental task that many animals face throughout life. Although social animals must cooperate, conflict over valuable resources such as food, territory, and mates is inevitable. To reduce conflict and facilitate group cohesion, social dominance hierarchies form readily and rapidly among social species, including humans. In this dissertation, I will explore human infants’ capacity to represent social dominance between groups. First, in a series of three studies, I will examine whether 6–12-month-old infants are sensitive to relative numerical group size. The first two studies suggest that infants expect an agent from a numerically larger group to be socially dominant. A third study ruled out lower-level alternative explanations for these findings. Building upon this work, I will investigate whether infants represent members of social groups as allies. Across three studies I will explore whether individual members of a social group are expected to assume specific roles and obligations during intergroup conflict. Together, the results from these studies suggest that infants as young as 9 months of age expect intervening agents to exclusively aid ingroup members during a conflict. However, it is also important to be able to assess whether allies have knowledge that there is a conflict and are present and available to intervene. In the final two studies I explored whether allies’ ability to see intergroup conflict occur would affect infants’ expectations of social dominance. These findings suggest that 9–12-month-old infants only expected the group with more agents that could see the conflict occur to prevail and be socially dominant. This suggests that infants are not only sensitive to the overall number of agents in each group, but also consider allies’ ability to provide aid during a conflict. Taken together, this work provides novel insights into the phylogenetic and ontogenetic origins of infants’ capacity to represent social dominance relationships and hierarchies.Arts, Faculty ofPsychology, Department ofGraduat