Concepts and Categories: Their Representation, Structure, and Process

Abstract

This thesis examines people's mental representation, membership structure and categorization processes with respect to concepts and categories. The aim of Experiment 1 was to discover whether three category-types (natural superordinate, property and ad hoc types) have graded structure. The study looked at two possible underlying causes for the gradience commonly found in the production frequencies of category instances: statistical artifacts or typicality structures. Results supported the hypothesis that people consult a common representation when they produce exemplars according to their degree of typicality. These results imply that all the instances in the three category-types have a normative, graded structure. The next experiment compared a normative graded structure with an idiosyncratic organization of membership. ... The thesis suggests that empirical studies should take the importance of subjective knowledge (as well as normative knowledge) into consideration when further empirical studies are carried out, for example, by using idiosyncratic stimuli. Theoretically, the three studies have shown that we have the categories we do because of the concepts we construct (rather than concepts being inductively derived to fit the naturally occurring categories in the world).