Category differentiation in object recognition: typicality constraints on the basic category advantage.

When people are asked to decide whether an object is in a given category, they generally respond faster when the category is at the basic level (e.g., car) than when it is at the superordinate level (e.g., vehicle) or the subordinate level (e.g., sedan). Basic categories have shorter and more frequent names, are learned earlier, and are usually more highly differentiated than other categories (they are both specific and distinctive), but it is not clear which of these factors is responsible for the faster response to basic categories. In three experiments with natural language categories, we found evidence that objects can be identified fastest as members of differentiated categories, even when such categories have longer names and are learned later than less differentiated categories. Specifically, we argued that atypical subordinate categories (e.g., racing car) are highly differentiated and should therefore be responded to as fast as basic categories in object recognition. The results supported this view and also ruled out the hypothesis that objects are necessarily identified as members of basic categories before further identification. We discuss the implications of these findings for the use of category names as definite descriptions in discourse.