Parts and the basic level in natural categories and artificial stimuli: comments on Murphy (1991)

Natural taxonomies consist of categories that vary in level of abstraction. Categories at the basic level, such as chair and apple, are preferred in a broad range of situations (Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976). Several studies have revealed qualitative differences between the basic level and other levels. For example, Tversky and Hemenway (1984) presented evidence that parts proliferative at the basic level; they proposed that parts link the appearance of category members with their functions. Although not taking issue with these findings, Murphy (1991) investigated whether parts are necessary or sufficient for a basic level. In an attempt to demonstrate that parts are not necessary, Murphy used artificial stimuli that did not capture the essential features of natural taxonomies. These discrepancies preclude any conclusions based on his studies. Murphy's data also do not support his claim that parts are not sufficient for a basic level. Finally, it is unlikely that pursuing questions of necessity or sufficiency will produce insights into human categorization.