EFFECTS OF PROTOTYPICALITY ON CATEGORIZATION IN 1-YEAR-OLDS TO 2-YEAR-OLDS - GETTING DOWN TO BASIC

Increasing evidence suggests that basic-level categories are a developmentally later achievement, resulting from differentiation of earlier global-level ones. Both within-category similarity and between-category constrast have been shown to be major determinants of categorization, and thus they are likely to affect differentiation as well. By varying exemplar prototypicality we examined the joint influence on differentiation of manipulations of within-category similarity and between-category contrast. Using object manipulation, we tested 13-, 16-, and 20-months-olds' (Experiment 1); and 24-and 28-months-olds' (Experiment 2) categorization of global- and basic-level object sets composed entirely of prototypical exemplars and of nonprototypical exemplars. Effects of prototypicality were parallel at the global and basic levels: Categorization of prototypical exemplars was superior to that of nonprototypical exemplars. Children behaved systematically toward categories of prototypical exemplars at an earlier age than towards categories of nonprototypical exemplars. The gap between categorization of prototypical and nonprototypical exemplars narrowed first at the global level of contrast (i.e., at 24 months) and later at the basic level of contrast (i.e., at 28 months). The research provides new information on the effects of prototypicality and on the process of differentiation of early global categories into more specific basic-level ones.