Cattell-Horn-Carroll cognitive abilities and their effects on reading decoding skills: g has indirect effects, more specific abilities have direct effects.

This study employed structural equation modeling to examine the effects of Cattell-Horn-Carroll (CHC) abilities on reading decoding skills using five age-differentiated subsamples from the standardization sample of the Wood-cock-Johnson III (Woodcock, McGrew, & Mather, 2001). Using the Spearman Model including only g, strong direct effects of g on reading decoding skills were demonstrated at all ages. Using the Two-Stratum Model including g and broad abilities, direct effects of the broad abilities Long-Term Storage and Retrieval, Processing Speed, Crystallized Intelligence, Short-Term Memory, and Auditory Processing on reading decoding skills were demonstrated at select ages. Using the Three-Stratum Model including g' broad abilities, and narrow abilities, direct effects of the broad ability Processing Speed and the narrow abilities Associative Memory, Listening Ability, General Information, Memory Span, and Phonetic Coding were demonstrated at select ages. Across both the Two-Stratum Model and the Three-Stratum Model at all ages, g had very large but indirect effects. The findings suggest that school psychologists should interpret measures of some specific cognitive abilities when conducting psychoeducational assessments designed to explain reading decoding skills.