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

Investigated differences that result from acquisition of category-level information based on experience with category members (induced) as opposed to direct presentation of prototypical values (given). A relational coding model of categorization was developed in which classification is based on a mixture of exemplar and prototype information. In 2 experiments, a total of 192 undergraduates learned about 2 ill-defined categories. Stimuli were geometric shapes varying along 4 binary-valued dimensions. For 3 groups of Ss, 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 Ss 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 judgments in all 3 groups. For Ss directly presented with prototype values, classification was based on a mixture of similarity to prototypes and to stored exemplars. In contrast, Ss who only received experience with exemplars appeared to base their category judgments solely on similarity to stored exemplars, even though they could accurately judge the prototype values. The 2 components of the mixture model are related to Ss' classification strategies and the nature of abstracted, category-level information. (23 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved).