Development of Categorical Exclusivity in Young Infants.

Previous research has shown that 3- to 4-month-old infants form a global categorical representation for cats that includes female lions, whereas 6- to 7-month-old infants differentiate between cats and lions. Three experiments using familiarization-novelty preference procedures attempted to determine whether the differentiation of a global categorical representation (in this case, the differentiation of lions and cats) is governed by maturational or experiential constraints. Experiment 1 replicated the basic finding that 3- to 4-month-old infants form a categorical representation for cats that excludes dogs, but includes female lions. Experiment 2 examined whether experience with cats and lions during familiarization would allow for categorical differentiation. Experiments 1 and 2 both began with an initial familiarization of 12 colored photographs of cats presented during six 15-second trials. Experiment 2 also provided a second familiarization experience that paired a familiar cat with a novel lion. The subsequent preference tests showed no reliable preference to observe novel lions over familiar cats. Dogs were preferred to cats and lions, but lions were not preferred to cats. In experiment 3, two cat-cat pairings were interspersed among the cat-lion pairings during the second familiarization period. Under these conditions, the infants exhibited preferences suggesting that the categorical representation for cats excluded both dogs and lions. (AC)