This article synthesizes published literature comparing the cognitive functioning of children who have math disabilities (MD) with that of (a) average-achieving children; (b) children who have reading disabilities (RD); and (c) children who have co-morbid disabilities (MD+RD). Average achievers outperformed children with MD on measures of verbal problem solving, naming speed, verbal working memory (WM), visual-spatial WM, and long-term memory (LTM). Children with MD outperformed co-morbid children on measures of literacy, visual-spatial problem solving, LTM, short-term memory (STM) for words, and verbal WM. Children with MD could be differentiated from children with RDonly on naming speed and visual-spatial WM. Differences in cognitive functioning between children with MD and average achievers were related primarily to verbal WM when the effects of all other variables (e.g., age, IQ, and other domain categories) were partialed out.

The purpose of the present study was to synthesize research that compares children with and without reading disabilities (RD) on measures of short-term memory (STM) and working memory (WM). Across a broad age, reading, and IQ range, 578 effect sizes (ESs) were computed, yielding a mean ES across studies of -.89 (SD = 1.03). A total of 257 ESs were in the moderate range for STM measures (M = -.61, 95% confidence range of -.65 to -.58), and 320 ESs were in the moderate range for WM measures (M = -.67, 95% confidence range of -.68 to -.64). The results indicated that children with RD were distinctively disadvantaged compared with average readers on (a) STM measures requiring the recall of phonemes and digit sequences and (b) WM measures requiring the simultaneous processing and storage of digits within sentence sequences and final words from unrelated sentences. No significant moderating effects emerged for age, IQ, or reading level on memory ESs. The findings indicated that domain-specific STM and WM differences between ability groups persisted across age, suggesting that a verbal deficit model that fails to efficiently draw resources from both a phonological and executive system underlies RD.

The results suggest a broad impairment in EF in adolescents with DS, and are consistent with several similar studies conducted with adults with DS. We assume that EF deficit is a characteristic of DS.

The influence of cognitive growth in working memory (WM) on mathematical problem solution accuracy was examined in elementary school children (N ϭ 353) at risk and not at risk for serious math problem solving difficulties. A battery of tests was administered that assessed problem solving, achievement, and cognitive processing (WM, inhibition, naming speed, phonological coding) in children in 1st, 2nd, and 3rd grade across 3 testing waves. The results were that (a) children identified as at risk for serious math problem solving difficulties in Wave 1 showed less growth rate and lower levels of performance on cognitive measures than did children not at risk; (b) fluid intelligence and 2 components of WM (central executive, visual-spatial sketchpad) in Wave 1 (Year 1) predicted Wave 3 word problem solving solution accuracy; and (c) growth in the central executive and phonological storage component of WM was related to growth in solution accuracy. The results support the notion that growth in WM is an important predictor of children's problem solving beyond the contribution of reading, calculation skills, and individual differences in phonological processing, inhibition, and processing speed.

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