Children monitor individuals' expertise for word learning.

Two experiments examined preschoolers' ability to learn novel words using others' expertise about objects' nonobvious properties. In Experiment 1, 4-year-olds (n = 24) endorsed individuals' labels for objects based on their differing causal knowledge about those objects. Experiment 2 examined the robustness of this inference and its development. Four-year-olds (n = 40) endorsed labels from confederates who accurately predicted objects' nonobvious internal properties but not nonobvious external properties. Three-year-olds (n = 40) performed at chance levels in both cases and were less likely to recognize the informants' expertise, suggesting that they might be unable to monitor individuals' expertise. These data suggest that children's ability to learn from testimony is necessary for their understanding of the relevance of an individual's expertise.