On domain differences in categorization and context variety

Membership in many natural categories is considered all-or-none, while membership in most artifact categories is found to be graded. We introduce an alternative for the prevailing view that this domain difference in categorization results from representational differences. The context variety account posits that an item's gradedness reflects the variety of contexts it appears in. Items that feature in a variety of contexts are assumed to be more likely to elicit a graded categorization response, since the suggested target category only provides one of many solutions to the question of the item's identity. We review earlier work that suggested a domain difference in context variety, with artifactual items appearing in a greater variety of contexts than natural ones. The context variety domain difference is established in two separate experiments but is shown not to explain the domain difference in categorization. A selection of artifactual and natural items, for which the domain difference in context variety is reversed, is presented for categorization in a third experiment. This selection, too, fails to provide evidence for the context variety account of categorization differences. The domain difference in categorization is shown to be robust against this manipulation. Context variety appears to have no bearing on categorization, so the context variety account is not a sustainable alternative to accounts that posit representational differences between natural and artifact categories.