Reasoning Beyond Explicit Rules: Adults' and Children's Use of Closure Principles in Novel Cases.

Learners often encounter situations where explicit rules fail to account for novel cases, leading to an underdetermination problem. One way to explore how learners navigate this uncertainty is to see if their inferences align with closure principles, through which a learner assumes that anything not explicitly prohibited is permitted, and anything not explicitly permitted is prohibited. Beyond permission and prohibition, normative inferences must also be made from and about a learner's obligations-not only what they can do, but what they must do. Contrary to adult learners, young children may make more restrictive inferences about how permissible or obligatory a novel action is, aligning with their well-documented "strict normativity". Across two studies, we explore inferences from adults (N = 115, Mage = 34.63) and 4- to 6-year-old children (N = 120, Mage = 5.48). Our findings suggest that while both adults and children rationally learn closure principles consistent with deontic logic, children's reasoning about prohibitions undergoes developmental changes. Contrary to adults, children taught explicit prohibitions were restrictive in their permissibility judgments until age 5. Thus, the framing of explicit rules leads to differing inferences about novel, unspecified cases across age and rule type.