Children’s understanding of how past experience shapes future expectations

When deciding how to act in new situations, we expect agents to draw on relevant prior experiences. This expectation underlies many of our mental state inferences, allowing us to infer agents’ prior knowledge from their current actions. Across three experiments (n = 264 4- to 6-year-olds recruited at testing sites with diverse populations), we find that four-year-olds share this expectation; however, it is not until age six that children reliably use this expectation to infer what and how much others know. This work suggests that even young children have principled expectations for how ignorance will lead agents to act—and six-year-olds may already understand that knowledge is graded rather than binary, able to infer which of two agents knows more.