Children's Understanding of How Past Experience Shapes Future Expectations.

As adults, we do not expect ignorant agents to behave randomly or always get things wrong. Instead, we expect them to act reasonably, guided by past experiences. We test whether 4-to-6-year-olds share this intuition and use it to infer others' knowledge, or whether they rely on a simple "ignorance = error" heuristic identified in past work. Across three pre-registered experiments (n = 264 4-to-6-year-olds recruited in the US between 2018-2022; demographic data not collected), we find that 4-year-olds expect agents to draw on past experiences when acting in new situations. However, only 6-year-olds reliably use this expectation to infer others' knowledge from behavior. These findings suggest that by age 6, children use a causal model of how ignorance shapes behavior, and not just a cue-based understanding of epistemic states.