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Recent analyses of natural kind terms (e.g., dog, gold) suggest that people expect members of a kind to share unforeseen properties. The present study investigated the development of this expectation by studying children's inductive inferences. On each of a series of problems, 3- and 4-year-old children were taught a new fact about an object and then were asked whether it would generalize to: an object that looked like the original, that had the same label as the original, that looked like the original and had the same label, or that differed from the original in both respects. The results indicate that 3- and 4-year-olds drew more inferences based on category membership than on perceptual appearances, when both were available. Furthermore, children often based their inferences on category membership even when no label was provided. Thus even 3-year-olds assumed that natural kind categories include more than superficial features.
Gelman et al. (Tue,) studied this question.