The Motor Performance of Educable Mentally Retarded and Intellectually Normal Boys after Covariate Control for Differences in Body Size

This study based on 12 motor performance and 7 anthropometric measures (71 educable mentally retarded and 71 intellectually normal boys of equivalent chronological age) confirmed early reports of the superiority of normal boys on motor performance tests. However, when adjustments were made for differences in body size by multivariate covariance analysis, nonsignificant differences were obtained on 5 of the 12 measures, namely the 35-yard (32.0 m) dash, the 150-yard (137.2 m) dash, knee flexion strength, knee extension strength, and sit-ups. Differences on these motor tasks can be explained less as a function of intelligence than as a function of body size inequalities.