Evaluation of exemplar-based generalization and the abstraction of categorical information

Examined whether a pure, exemplar-based abstraction process is an adequate model of category learning or whether it is necessary to postulate an additional prototype-abstraction process. D. Homa et al examined this question in an experiment in which Ss classified high-level distortions of prototype patterns into categories and were later given transfer tests that included new, old, and prototype exemplars. Based on quantitative discrepancies from a pure, exemplar-based model, Homa et al argued that it was necessary to recognize the operation of a prototype-abstraction process in order to fully explain their results. However, Homa et al never actually fit the exemplar plus prototype model to the data to determine if indeed the additional prototype process could explain the deviations from the pure exemplar model. The present study compared the pure exemplar model with a mixed (exemplar plus prototype) model and did not find consistent evidence requiring the postulation of an additional prototype-abstraction process. These results point out the difficulty of distinguishing alternative classification models. (7 ref)