The relative contributions of common and distinctive information on the abstraction from ill-defined categories

In a study with 54 undergraduates, the abstraction of prototypical information and the classification of new exemplars were investigated as a function of category size and the number of categories that had to be distinguished during learning. It was argued that category size should influence primarily the abstraction of information common to that category, whereas the number of categories that had to be distinguished during learning should provide for the isolation of distinctive features among the categories. Results indicate that when 4 or 6 categories were distinguished, category size (3 vs 6 exemplars per category) had a facilitative effect on the classification of the prototype and new exemplars; the effect of category size was minimal when there were 2 categories. In addition, conversion to d' values revealed a slight main effect of the number of categories on prototype abstraction. It is concluded that both variables are operative in the abstraction from ill-defined categories, but that the influence of common and distinctive features may occur at different stages of learning. A secondary result was that rapid learners were also superior abstractors, although even the slowest learners benefited by category size. (16 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved).