Proceedings of the Annual Meeting of the Cognitive Science Society

An experiment investigating effects of familiarity (indicated by presentation frequency) on categorization and recognition behavior is presented. Results show frequency influenced performance under speeded response conditions only, producing increased categorization of new, similar items with the frequent item, and differentiation (a decrease in false alarms to these same items) in recognition. These results are evaluated with respect to different versions of an exemplar model of categorization and recognition (Medin & Schaffer, 1978; Nosofsky, Clark & Shinn, 1989). Models that include a mechanism for differentiation, or changes in the similarity computation to a familiar example, provided better descriptions of both categorization and recognition behavior than models without this added aspect. The addition of a differentiation mechanism improved flts to categorization data of all three versions of exemplar models considered: the type model (in which repetitions do not produce separate memory traces), the toicen model (which posits individual memory traces for each repetition of an item) and the frequency parameter model (wiiich iiKludes frequency weighting as a free parameter).