Abstract
There is long-standing evidence for verbal working memory impairments in both children and adults with dyslexia. By contrast, spatial memory appears largely to be unimpaired. In an attempt to distinguish between phonological and central executive accounts of the impairments in working memory, a set of phonological and spatial working memory tasks was designed to investigate the key issues in working memory, task type, task demands (static, dynamic, and updating), and task complexity. Significant differences emerged between the dyslexic and nondyslexic participants on the verbal working memory tasks employed in Experiment 1, thereby providing further evidence for continuing dyslexic impairments of working memory into adulthood. The nature of the deficits suggested a problem with the phonological loop, with there being little evidence to implicate an impairment of the central executive. Due to the difficulties associated with separating verbal working memory and phonological processing, however, performance was investigated in Experiment 2 using visuospatial measures of working memory. The results of the visuospatial tasks indicated no between-group differences in static spatial memory, which requires the short-term storage of simultaneously presented information. In almost all conditions there were no between-group differences in dynamic spatial memory that demands the recall of both location and order of stimuli presented sequentially. However, a significant impairment occurred on the dynamic task under high memory updating load, on which dyslexic adults showed nonphonological working memory deficits. In the absence of an explanation involving verbal recoding, this finding is interpreted in terms of a central executive or automaticity impairment in dyslexia.
Highlights
Developmental dyslexia is a condition that affects approximately 5% of the population in the western world (Badian, 1984)
Consistent with previous studies of verbal working memory in dyslexia (e.g., Jorm, 1983; Miles, 1983; Cohen, Netley, & Clarke, 1984; Ackerman & Dykman, 1993), significant dyslexic impairments were uncovered on both the digit and word span tasks
The poor performance at the early serial positions implicates a failure of the articulatory control process
Summary
Developmental dyslexia is a condition that affects approximately 5% of the population in the western world (Badian, 1984). Jorm, 1983; Cohen, Netley, & Clarke, 1984; Ackerman & Dykman, 1993; Brunswick, McCrory, Price, Frith, & Frith, 1999; Pennington, Cardoso-Martins, Green, & Lefly, 2001; Roodenrys & Stokes, 2001; Wilson & Lesaux, 2001; McDougall & Donohoe, 2002; Plaza, Cohen, & Chevrie-Muller, 2002), the source of these problems, whether it be verbal working memory per se or phonological processing, remains unclear. This has led to some controversy over the amount of group variance attributable to deficits in phonological or memory processes (e.g. Gathercole, Willis, Emslie, & Baddeley, 1991; Snowling, Chiat, & Hulme, 1991; Gathercole, 1994)
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