Preschoolers' default assumptions about word meaning: Proper names designate unique individuals

Ninety 4-year-olds took part in this experiment. Children heard a novel word (e.g., ''X'') uttered in an ambiguous sentence frame (e.g., ''This Y is X,'' where ''Y'' was a basic-level count noun, such as ''dog'') and applied to either 1 or 2 drawings of familiar animals. This word could be construed either as a proper name (e.g., ''This dog is Fred'') or as an adjective (e.g., ''This dog is red''). Children were more likely to interpret the word as a proper name (and less likely to interpret it as an adjective) if it was applied to 1 than if it was applied to 2 objects. Children thus made a default assumption that, in order to be a proper name, a word should be applied to only 1 individual. However, children overrode this default assumption if sufficient contextual information (from additional syntactic cues) indicated that they should do so.