Preschoolers use pedagogical cues to guide radical reorganization of category knowledge.

In constructing a conceptual understanding of the world, children must actively evaluate what information is idiosyncratic or superficial, and what represents essential, defining information about kinds and categories. Preschoolers observed identical evidence about a novel object's function (magnetism) produced in subtly different manners: accidentally, intentionally, or demonstrated communicatively and pedagogically. Only when evidence was explicitly demonstrated for their benefit did children reliably go beyond salient perceptual features (color or shape), to infer function to be a defining property on which to base judgments about category membership. Children did not show this pattern when reasoning about a novel perceptual property, suggesting that a pedagogical communicative context may be especially important for children's learning about artifact functions. Observing functional evidence in a pedagogical context helps children construct fundamentally different conceptions of novel categories as defined not by superficial appearances but by deeper, functional properties.