Evidence for Knowledge–Based Category Discrimination in Infancy

Two studies examined whether infants’ category discrimination in an object–examination task was based solely on an ad hoc analysis of perceptual similarities among the experimental stimuli. In Experiment 1A, 11–month–olds examined four different exemplars of one superordinate category (animals or furniture) twice, followed by a new exemplar of the familiar category and an exemplar of the contrasting category. Group A ( N = 39) explored natural–looking toy replicas with low between–category similarity, whereas group B ( N = 40) explored artificial–looking toy models with high between–category similarity. Experiment 1B ( N = 40) tested a group of 10–month–olds with the same design. Experiment 1C ( N = 20) reversed the order of test trials. For Experiment 2 ( N = 20), the same artificial–looking toy animals as in Experiment 1 (group B) were used for familiarization), but no category change was introduced at the end of the session. Infants’ responses varied systematically only with the presence of a category change, and not with the degree of between–category similarity. This supports the hypothesis that performance was knowledge based.