Machine Learning 3: 343-372, 1989 @ 1989 Kluwer Academic Publishers - Manufactured in The Netherlands Conceptual Clustering, Categorization, and Polymorphy STEPHEN JOSl~ HANSON t (
[email protected]) Bell Communications Research, 435 South Street, Morristown, NJ 07960, U.S.A. MALCOLM BAUER (
[email protected]) Cognitive Science Laboratory, Princeton University, 221 Nassau Street, Prineeton~ NJ 08542, U.S.A. (Received: October 1, 1986) (Revised: October 31, 1988) Keywords: Conceptual clustering, categorization, correlation, polymorphy, knowledge structures, coherence Abstract. In this paper we describe WITT, a computational model of categoriza- tion and conceptual clustering that has been motivated and guided by research on human categorization. Properties of categories to which humans are sensitive include best or prototypieal members, relative contrasts between categories, and polymor- phy (neither necessary nor sufficient feature rules). The system uses pairwise feature correlations to determine the "similarity" between objects and clusters of objects, allowing the system a flexible representation scheme that can model common-feature categories and polymorphous categories. This intercorrelation measure is cast in terms of an information-theoretic evaluation function that directs WITT'S search through the space of clusterings. This information-theoretic similarity metric also can be used to explain basic~level and typicality effects that occur in humans. WITT has been tested on both artificial domains and on data from the 1985 World Almanac, and we have examined the effect of various system parameters on the quality of the model's behavior. 1. Introduction The majority of machine learning research has followed AI in using logic or predicate calculus for the representation of knowledge. Such logical formalisms have many advantages: they are precise, general, consistent, powerful, and extensible, and they seem distantly related to natural language.