On the Relationship between Categorization and Similarity Judgments

Jean-Pierre Thibaut

Abstract Thibaut and Dupont (1997) replicated a dissociation between categorization and similarity obtained by Rips (1989). In his experiment, Rips found that a stimulus half-way between a pizza and a quarter was categorized as a pizza but was rated as more similar to a quarter. In their experiment, Thibaut and Dupont (1997) presented unknown stimuli composed of a non salient necessary feature combined with a salient characteristic feature. Participants categorized the stimuli on the basis of the necessary feature and made their similarity judgments on the basis of the characteristic feature. However, Thibaut and Dupont failed to obtain this dissociation in one of their experimental conditions. They hypothesized that the origin of this failure was to be found in the fact that subject did not notice the association between the characteristic feature and the corresponding category. In the present paper, by introducing a free sorting task, subjects produced the dissociation in the condition in which they did not produce it in Thibaut and Dupont. The results are discussed in terms of the role of necessary and characteristic features. I also propose a distinction between categorization and similarity judgments, and an interpretation of the dissociation in terms of the feature space.