Validity of the V. C. Aeronautics Aptitude Test and the O. E. Scientific Aptitude Test

An hierarchical factor solution was obtained on correlations among WISC and ITPA subtests for 110 reading disabled children. The ability hierarchy which included a general (g) factor, two subgeneral factors, and five primary factors was arranged in a manner congruent with Vernon's structural paradigm. The g-factor was defined by a moderate but distinct pattern of positive loadings from WISC and ITPA subtests. At the subgeneral level a verbal-educational factor was defined by verbal WISC and ITPA subtests, and a spatial-perceptual-mechanical factor was defined by WISC performance and ITPA visual subtests. Three primary factors—freedom from distractibility, verbal precision, and quasi-specific—were defined by WISC subtests. Two primary factors—automatic processes and representational processes—were defined by ITPA subtests.