Retarded, normal, and superior Ss were compared on their grouping object-level words by criteria at two levels of inclusiveness. With MA held constant, the groups did not differ in level of concept attainment. With CA held constant, the groups did differ: the superior exceeded the retarded and normal; and the normal exceeded the retarded. The groups did nor respond differentially to rhe two levels of inclusiveness; and so, relationships between the groups remained constam at both levels.