DIFFERENTIAL ABILITY SCALES-II PREDICTION OF READING PERFORMANCE: GLOBAL SCORES ARE NOT ENOUGH

This study investigated the effects of broad cognitive abilities derived from the Cattell Horn Carroll (CHC) taxonomy, together with the effect of the general factor (g), on Wechsler Individual Achievement Test, Second Edition (WIAT-II) reading achievement. Structural equation modeling (SEM) and commonality analyses were applied to the Differential Ability Scales, Second Edition (DAS-II) standardization and clinical sample data. All seven DAS-II CHC broad cognitive abilities were shown to have significant effects on one or more WIAT-II reading domains with different patterns found across typical, poor reader, and reading specific learning disability (SLD) groups. In the SEM analyses, the general factor g had only indirect effects on reading achievement variance. In the commonality analyses, after the effects of the seven CHC factors had been accounted for, the six-factor commonality-which could be considered an alternative measure of global intelligence-accounted for only 1%-2% of reading measure variance. For children who are having difficulties with reading skill acquisition, the data suggest that primary emphasis on g will result in a major loss of DAS-II predictive validity. Results emphasize the importance of having a comprehensive cognitive assessment with the DAS-II in the evaluation of reading competency and disability. Links between CHC broad ability factors and neuropsychological constructs may provide a promising foundation for developing specific cognitive, academic, and behavioral interventions for children with reading SLD. (C) 2010 Wiley Periodicals, Inc.