Studies on the formation of perceptually based basic-level categories in young infants.

A series of experiments examined the abilities of 3- and 4-month-old infants to form categorical representations to exemplars of natural kinds--cats and horses. These experiments also permitted assessment of the relative exclusivity of these representations--the extent to which they exclude exemplars from contrasting basic-level categories from the same superordinate category. We found that categorical representations could be formed for horses that excluded cats, zebras, and giraffes, and for cats that excluded horses and tigers but not female lions. Lions were, however, excluded from the representations of cats in 6- and 7-month-old infants. Evidence was also obtained for 2 a priori preferences for members of one category over another. The discussion examined the roles of similarity between the exemplars of the contrasting categories and those of the tested category on estimates of exclusivity and of spontaneous preferences on the formation and exclusivity of categorical representations.