Gettier intuitions are robust in children and adults

A central debate in cognitive science concerns whether knowledge or belief is the primary cognitive attitude in our Theory of Mind. "Knowledge-First" accounts posit that knowledge is a fundamental, while traditional "Belief-First" accounts view it as a complex derivative of belief. Gettier cases, where justified true belief can fall short of knowledge, serve as a cornerstone of this debate. We tested the robustness and developmental trajectory of this intuition, and its relation to belief-desire psychology. Across three studies using novel, non-verbal video vignettes we found that both adults and children (5-8 years) systematically denied knowledge in Gettier tasks. Crucially, while the experimental task (True Belief vs. Gettier cases) strongly influenced knowledge attributions, it had little direct effect on action predictions in adults and children. The key factor influencing action prediction in adults was whether participants had attributed or denied knowledge beforehand. Despite all participants attributing the relevant belief, when knowledge was denied, participants became significantly slower and more uncertain in their predictions. Our findings are compatible with dual-process accounts, suggesting the primacy of knowledge in theory of mind.