Infants' use of object parts in early categorization.

Two experiments involving object-manipulation tasks were performed to examine whether 1- to 2-year-olds form superordinate-like categories by attending to object parts. In Study 1, 14-, 18-, and 22-month-olds were tested with contrasts of animals, furniture, insects, and vehicles. Fourteen- and 18-month-olds behaved systematically toward categories with different parts (legs or wheels) but not toward categories with matching parts (legs or legs). In Study 2, infants were tested with novel animals and vehicles generated by removing or attaching legs or wheels. In the absence of part differences, all three age groups failed to form superordinate categories. The two younger groups chose to categorize by parts (i.e., legs or wheels) rather than by category membership (animal or vehicle). The results suggest a perceptual basis for categorization whereby infants form dynamic categories, on-line, that are based on the characteristics of the input.