On the relationship between category intensions and extensions in children.

We contrasted four theories of natural language category acquisition by investigating the relation between category intensions and extensions in children (kindergarteners, second graders, fifth graders) and in college students. Everyone was asked to define a category term, to make category membership judgments of possible exemplars, and to judge whether the possible exemplars possessed features generated by them and by previous adult subjects. Adult judges were also asked to judge whether the possible exemplars possessed the features generated by the subjects. Children's intensions and extensions were very consistent. In addition, children's extensions were reliably smaller than adults', and the features which children generated were more specific than those generated by adults. None of the existing theories discussed can explain this pattern of results. An exemplar-based model is proposed to do so.