Four-year-olds' disambiguation of action and object word reference.

Preschool-age children show a very strong tendency to map a novel noun onto an unfamiliar rather than a familiar object. This so-called disambiguation effect has been interpreted as evidence that youngers expect object labels to be mutually exclusive. In Experiment 1, 4-year-olds were observed to map a novel verb onto an unfamiliar action about twice as often as they mapped it onto a familiar one. When the unfamiliar action had been preexposed, but the familiar one had not, the mapping preference was eliminated. In Experiment 2, 4-year-olds mapped a novel noun onto an unfamiliar object about five times as often as they mapped it onto a familiar object, and this tendency was not affected by preexposure. Even when action embedding and question complexity were controlled, the disambiguation effect was stronger for object than for action words. An account is presented in which two lexical principles, Mutual Exclusivity and Feeling of Novelty, are hypothesized to apply differently to action than to object words.