Recently a three stratum theory of intelligence that combines the major aspects of Spearman~s theory of general intelligence (g) (1927) and Horn and Cattell's theory of crystallized and fluid intelligence (Gf-Gc) (1991) has been proposed (Carroll, 1993). The purpose of this study was to test the three stratum theory using confirmatory factor analysis with the LISREL computer program. Developmental changes in the structure of intelligence were also investigated. Results provided support for the three stratum theory, suggesting the possibility of intermediate factors between the second and third stratum but no support for developmental changes in the organization of cognitive abilities. / Ph. D.