Two studies with 3-, 4-, and 5-year-olds examined whether young children can differentiate expertise in the minds of others. Findings indicated that all children could correctly attribute observable knowledge to familiar experts, such as a car mechanic. Preschoolers had difficulty making attribution of knowledge of scientific principles to unfamiliar experts. A computational analysis indicated that success could not be attributed to the way in which words co-occur in discourse. (Author/KB)