AN INVESTIGATION OF THE DEVELOPMENTAL AND DIFFERENCE THEORIES OF RETARDATION UTILIZING PROFILE ANALYSIS OF WISC-R SCORES

MARTIN GARY GROFF, Purdue University

Abstract

The goals of the present study were to test predictions derived from developmental and difference theories of retardation and to investigate developmental changes in the intellectual strengths and weaknesses of retardates. Two groups of familial retarded youth and one group of average ability youth constituted the subjects of this investigation. The younger retarded group (N = 50) had chronological ages (CAs) of approximately 9 1/2 years. The older retarded group (N = 50) had Wechsler Intelligence Scale for Children - Revised (WISC-R) Mental Ages (MAs) of approximately 9 1/2 years, and the nonretarded group (N = 50) had CAs and WISC-R MAs of roughly 9 1/2 years. Profile analysis within the framework of Hotelling's T('2) test for two independent samples was utilized in order to contrast WISC-R Verbal subtest Scaled Scores, Performance subtest Scaled Scores, and Factor Scores of the three groups. The Factor Scores were averages of Scaled Scores from subtest combinations proposed by Kaufman. Between-group comparisons of WISC-R scores were conducted for (1) the younger retarded and the nonretarded group, (2) the older retarded and the nonretarded group, and (3) the younger retarded and the older retarded group. Profile analysis contrasts offered no evidence of important differences in the intellectual strengths and weaknesses of the retarded and nonretarded groups of equivalent MA. The results were interpreted as supporting Zigler's developmental view of retardation, which has asserted that retarded and nonretarded persons of equivalent MA possess similar intellectual abilities. Some differences were found in the intellectual strengths and weaknesses of the retarded and nonretarded groups of equivalent CA. However, these differences could not be related clearly to a difference-theory prediction of dissimilar strengths and weaknesses for retarded and nonretarded persons, because the difference view of retardation was vague concerning the specific abilities expected to manifest different patterns in retardates and controls. Developmental changes in the intellectual strengths and weaknesses of retardates were suggested by the results of WISC-R score comparisons of the younger retarded and older retarded groups. The most notable trend was a comparative decline with maturation in verbal comprehension and attention skills and a relative improvement in perceptual organization abilities. A significant WISC-R Performance IQ elevation was observed for the average ability group and for the older retarded group. The Performance IQ elevation of the nonretarded group raised questions about the representativeness of this sample and about the intellectual characteristics of subgroups of nonretarded persons. The findings of this study would seem to have implications for curriculum planning and mental retardation research. The close correspondence in intellectual strengths and weaknesses of the older retarded and nonretarded groups suggests that it may be appropriate to use similar educational methods with retarded and nonretarded youth of equivalent MA. However, the differences in intellectual strengths and weaknesses of the two retarded groups suggest that age-related changes in instructional strategies may promote optimal learning in retarded youth. Moreover, the apparent maturational changes in retardates' ability patterns caution against attempts to characterize the cognitive attributes of retarded samples having heterogeneous CAs. To verify the findings of the present study and to increase the generalizability of results, recommendations for further research focused on using the WISC-R standardization data for investigating the intellectual strengths and weaknesses of retarded and nonretarded persons at various CA and MA levels.

Degree

Ph.D.

Subject Area

Special education

COinS