Cognitive processing of low achievers and children with reading disabilities: A selective meta-analytic review of the published literature

This article synthesizes some of the published literature comparing the cognitive functioning of children with reading disabilities (RD) and children with low reading and low intelligence (low achievers). Nineteen studies, which yielded 274 effect sizes (ESs), indicated that children with reading disabilities outperformed low achievers (LA) on measures of lexical knowledge, syntactical knowledge, and visual-spatial processing (ES means =.55, .87, .36, respectively), but not on measures of phonological processing [e.g., ES mean =.25 for pseudo-ward reading, ES mean = -.06 for automaticity (rapid naming)]. Regression modeling indicated that the magnitude of effect size differences on cognitive measures between RD and LA children was significantly related to chronological age (older participants yield smaller effect sizes than younger participants) and verbal IQ (the greater the difference in IQ between RD and LA participants the larger the effect size). Model testing further supported the hypothesis that relative to other cognitive measures, children with RD share a common phonological core deficit with LA achievers. However, the results indicated that the deficits shared between these two groups are much broader than a phonological core. The results were discussed within the context of defining children with RD by discrepancy criteria and how advances in the classification of such children might occur.