Abstract

The purpose of this study was to examine the developmental theory and the difference theory which explain the intellectual ability of the mentally retarded children. The developmental sequence and the developmental level of the conceptual organization(thematic organization and taxonomic organization) between 4-year-old normal children and mentally retarded children were compared. The results of this study were as follows. The correct response of thematic organization was higher than that of taxonomic organization in both of normal children and mentally retarded children. The correct response of thematic organization and taxonomic organization was not different significantly between the normal children and the mentally retarded children. The correct response of no-relation condition of the normal children was significantly higher than that of the mental retarded children. The findings of this study support not only the developmental theory, but also the difference theory of the intellectual ability of mentally retarded children.