Overrated adults: 4-year-olds’ false belief understanding is influenced by the believer’s age

•4- and 5-year-olds inferred false beliefs (FB) in either an adult or a child.•4-year-olds performed below chance when identifying FB in an adult.•4-year-olds performed at chance when identifying FB in a child.•5-year-olds performed above chance when identifying FB in either protagonist. Children perceive adults as more knowledgeable than peers. We tested whether this general preconception influences preschoolers’ performance in a false-belief task. Children (4- and 5-year-olds; N = 146) watched videos showing a peer protagonist or an adult protagonist experiencing events that should lead the protagonist to hold a false belief. Then children were asked to infer the protagonist’s perception of the situation. Age of the protagonist influenced 4-year-olds’ judgments but not 5-year-olds’ judgments. Specifically, 4-year-olds’ performance was at chance when presented with a peer protagonist. Their performance dropped further when presented with an adult protagonist and was significantly below chance. Children aged around 5 years performed above chance level regardless of whether they were presented with an adult or peer protagonist. This suggests that in the younger age group, children’s tendency to regard adults as experts in general knowledge undermined their ability to accurately judge the possibility that an adult could hold a false belief.