Development of the formation of categories by normal and retarded persons.

Abstract

The purpose of this study was to investigate the development and fragmentation of categories over chronological and mental age without the requisite of free recall. Kindergarten, fourth-grade, and ninth-grade students and a noninstitutionalized group of retarded students labeled and categorized 480 chromatic slides of picturable objects. Results showed that as age increased (a) more categories and superordinates congruent with adult criteria were elicited, (b) more superordinates were formed with more items per superordinate, (c) fragmentation of categories increased, and (d) the normal groups were more efficient in the formation of reliable categories than the retarded group. The results were compared with other developmental and comparative studies in clustering, with the emphasis on the importance of the availability and accessibility of superordinates in the development of clustering ability.