Effects of cognitive abilities on child and youth academic achievement: Evidence from the WISC-V and WIAT-III

The relations between children and adolescents' cognitive abilities and their reading, writing, and math achievement were examined using the Wechsler Intelligence Scale for Children, Fifth Edition and Wechsler Individual Achievement Test, Third Edition co-norming sample. We tested and compared models that included effects from the Cattell-Horn-Carroll broad cognitive abilities and models that focused on the effects of g only. Developmental differences in the patterns of cognitive-achievement effects were tested for statistical significance using interaction terms. Comprehension-knowledge exerted direct effects on all reading and most writing skills, fluid reasoning exerted direct effects on essay writing and math skills, and processing speed exerted direct effects on reading fluency, math fluency, and math calculation skills. Working memory significantly influenced most of the achievement skills and was particularly important for younger children. The effect of g on all achievement skills was strong, but indirect through the broad abilities and often overlapped with the effect of fluid reasoning. Results from this study suggest that children and adolescent's reading, math, and writing are differentially influenced by their cognitive abilities, and some of these effects vary by age.