The Department of Brain and Cognitive Sciences in Partial Fulfillment of the Requirements for the Degree of Master of Science in Brain and Cognitive Sciences

Three studies look at whether the assumption of causal determinism (the assumption that all else being equal, causes generate effects deterministically) affects children's imitation of modeled actions. We show that, even when the frequency of an effect is matched, both preschoolers and toddlers imitate actions more faithfully when modeled actions are deterministically rather than probabilistically effective. A third study suggests that preschoolers' imitation is affected, not just by whether the'agent's goal is satisfied but also by whether the action is a reliable means to the goal. Children's tendency to generate variable responses to probabilistically effective modeled actions could support causal learning. Thesis Supervisor: Laura Schulz Title: Assistant Professor of Cognitive Science DIFFERENTIAL IMITATION 3 Running head: DIFFERENTIAL IMITATION Judicious imitation: Children differentially imitate deterministically and probabilistically