Class structure in the biasing of perceived pattern similarity

Current judgment models underlying multidimensional scaling assume that perceived interstimulus proximity is determined solely by intradimensional differences between stimuli, independent of context effects. Class structure represents a context effect, with class centroids constituting multidimensional anchors within a configuration. The dependence of proximity judgments on class structure was examined in 3 experiments to test the appropriateness of the multidimensional scaling (MDS) judgment model for configurations containing element clusters. A total of 76 undergraduates served as Ss. Stimuli were multidimensional patterns generated to form 2 classes. Feature usage in judgments of intraclass similarity differed markedly from that in interclass similarity judgments. Moreover, the perceived similarities of 90 between-class pairs were in part determined by the distances of the pair members from class centroids, as well as by intradimensional differences. The partial context dependence of subjective proximity estimates suggests a source of incompleteness of the current MDS judgment model as applied to class structured events. (24 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved).