Defining features of natural kinds and artifacts

Two experiments investigated the role of three types of features (physical characteristics, functions, and chromosomal/molecular structure) in determining membership in natural kind and artifact categories. In the first, subjects decided if an object X would still be an X if it were different in one type of feature. A significant interaction was found between word type and change type, with the effects of chromosomal/molecular changes significantly greater for natural kinds than for artifacts, and the effects of functional changes significantly greater for artifacts than natural kinds. In the second experiment, subjects judged whether something would be an X if it were unlike instances of X in two of the above types of features, but like instances of X in one. There was again a significant interaction, with the effects of chromosomal/molecular features significantly greater for natural kinds than for artifacts, and the effects of functional changes significantly greater for artifacts than for natural kinds. These results suggest that chromosomal/molecular features define membership in natural kind categories and functional features define membership in artifact categories. The implications of these findings for the meaning of defining features are also discussed.The first experiment was conducted by the first author as part of a senior comprehensive exercise at Carleton College. We thank Kathleen Galotti, Matthew Gish, Neil Lutsky, and an anonymous reviewer for comments on earlier drafts of this article.