Given versus induced category representations: Use of prototype and exemplar information in classification.

Abstract

Acquisition of category-level information can be based on experience with category members (induced) as well as on direct presentation of prototypical values (given). To investigate the effects of these two types of information, a relational coding model of categorization was developed in which classification is based on a mixture of exemplar and prototype information. In two experiments, subjects learned about two ill-defined categories. Stimuli were geometric shapes varying along four binary-valued dimensions. For three groups of subjects, training consisted of (a) experience with exemplars only, (b) learning prototype values followed by exemplar experience, or (c) learning prototype values concurrently with exemplar experience. Following training, all subjects received classification tests on prototype values as well as on old and new exemplars. By varying the relative use of prototype and exemplar information, the mixture model accurately accounted for category judgements in all three groups. For subjects directly presented with prototype values, classification was based on a mixture of similarity to prototypes and to stored exemplars. In contrast, subjects who only received experience with exemplars appeared to base their category judgements solely on similarity to stored exemplars, even though they could accurately judge the prototype values. The two components of the mixture model are related to subjects' classification strategies and the nature of abstracted, category-level information.

Prototype and Exemplar-Based Information in Natural Language Categories

“…To our best knowledge, this is the first study in which predictions of the prototype view and of the exemplar view are compared to predict category-based decisions for natural language concepts. Our results differ somewhat from the findings in the majority of papers that have investigated category learning, where it is assumed that all previously encountered exemplars of a category are stored and are activated whenever category-related decisions have to be made (Gluck & Bower, 1988;Medin, Altom, & Murphy, 1984;Medin, Dewey, & Murphy, 1983;Medin & Schaffer, 1978;Nosofsky, 1987Nosofsky, , 1988Nosofsky, , 1991. The data presented here suggest that activation of a limited number of frequently generated exemplars of the studied concepts suffices to predict typicality ratings, response times, exemplar-generation frequencies, and category-naming frequencies significantly and that elaborating the exemplar set can even decreases the predictive power.…”

Neural dynamics of autistic behaviors: Cognitive, emotional, and timing substrates.

“…Some evidence suggests that exemplars, or individual experiences, can be learned and remembered, like those of familiar faces (Medin, Altom, and Murphy, 1984;Medin and Shaffer, 1978;Medin and Smith, 1981). However, this cannot be the final answer to this question, since storing every exemplar, or at least every memory as an exemplar, can lead to a combinatorial explosion of memory storage, to unwieldy memory retrieval, and to an inability to learn general or abstract properties of the world.…”

Reference Price and Price Perceptions: A Comparison of Alternative Models

“…Following this view, the reference price that consumers use to evaluate a product is a weighted average of the prices from the relevant category (Monroe 1990). The adaptation-level model of reference price comparison is consistent with a prototype representation of categories in which a single prototypical value is abstracted from category instances and is used to represent the category (Medin, Altom, and Murphy 1984).…”

“…In the psychological literature, exemplar models have consistently outperformed prototype models in empirical comparisons (Ashby and Maddox 1998). Exemplar models assume that judgments are based on comparisons to specific category members rather than a comparison to summary information about a typical member (Medin et al 1984). The exemplar model of categorization is consistent with a conceptualization of reference price as a range of prices or the latitude of acceptable prices rather than a single summary price (e.g., Janiszewski and Lichtenstein 1999;Kalyanaram and Little 1994;Lichtenstein and Bearden 1989;Monroe 1971).…”