Development of children's understanding of basic-subordinate inclusion relations.

Four studies focused on developmental differences in the representation of basic-subordinate inclusion relations. Tests of comprehension and production of category names, induction, and responses to direct questions pertaining to inclusion revealed a marked developmental gap between the production of subordinate category names and complete understanding of basic-subordinate inclusion relations. However, even 3-year-olds showed rudimentary knowledge of the asymmetry of inclusion. Discrepancies between children's performance on categorization tasks involving familiar and unfamiliar subordinate categories suggest that understanding of the logical nature of inclusion relations is constructed through the integration of categorical knowledge from familiar domains. Interactions among the knowledge base, pragmatic sensitivity, and information processing efficiency in the development of inclusion are discussed.