Themes as prototypes: Similarity judgments and categorization tasks in musical contexts

Abstract

Similarity judgments and corresponding categorizations often differ, as the former does not predict the latter (Keil, 1989). Prototype-based models suggest that categorization emphasizes features which distinguish contrasting prototypes from each other, features which may have a lesser role in free similarity ratings (Medin, Goldstone & Gentner, 1993; Rosch, 1988). We studied this effect in musical contexts, examining how specifying contrasting musical themes as frames of reference affects listeners categorizations of other extracts in the same composition, and comparing categorizations with corresponding similarity judgments. Musical materials employed in Lamont & Dibben s similarity rating experiment (2001), extracted from piano pieces by Beethoven and Schoenberg, were used. Participants independently marked, for each piece, to what degree extracts belong to each of its two main themes. These categorizations were compared with similarity ratings in the above study and with published thematic analyses of the 2pieces, and were correlated with combinations of diverse musical features of the themes. Categorizations concurred with similarity ratings for Beethoven, and differed for Schoenberg. However, despite participants independent ratings of affiliations with the two themes, in both pieces categorizations, unlike similarity ratings, were negatively correlated: the stronger an extract s affiliation with a theme, the weaker its affiliation with a contrasting theme. This effect resulted in some dramatic disparities between similarity ratings and corresponding categorizations. In addition, correlating listeners categorizations with musical features generated a graded categorystructure, where an extract s affiliation with a theme correlated with the number of distinctive surface features it shared with this theme. We suggest that musical themes serve as concrete prototypes for other events in the piece. Presenting contrasting themes emphasizes their distinctive features, thus creating an intraopus field of similarities and differences which characterizes the piece. Within that field, rival prototypes, represented by the main themes, compete to add incoming events to their sphere.