Nature and Origins of Intuitive Psychology in Human Infants

Abstract

We cannot help but see ourselves and others as intentional agents, who have goal states of the world in mind and plan costly actions in order to realize them. In this thesis, I investigate the origins of these abilities in human infants, and aim to describe these origins in engineering-specific terms. I ask: What are the representations and computations that support infants’ understanding of other people and their actions? I argue that infants use an abstract, coherent theory of psychology to explain and predict other people’s actions. I present evidence that when infants observe other agents act, they appreciate that agents seek to minimize the cost of their actions (Paper 1: Liu & Spelke, 2017, Cognition), trade off the cost of acting against the rewards actions bring (Paper 2: Liu, Ullman, Tenenbuam, & Spelke, 2017, Science), and act so as to cause changes in the world (Paper 3: Liu, Brooks, & Spelke, 2019, PNAS). Across all of these studies, infants flexibly apply this reasoning to agents that are unfamiliar to them, and to actions that they themselves are incapable of performing. I end by speculating on infants’ co-developing intuitive physics and psychology and their understanding of agentic and physical causation. Collectively, this work shows that human infants rapidly come to see other people as intentional causal agents acting in a physical world.