Dyslexia and dyscalculia: Two learning disorders with different cognitive profiles
aDepartment of Psychology, University of Tuebingen, 72072 Tuebingen, Germany
bDepartment of Psychology, University of Salzburg, 5020 Salzburg, Austria
Received 13 August 2008; revised 9 March 2009. Available online 26 April 2009.
This study tests the hypothesis that dyslexia and dyscalculia are associated with two largely independent cognitive deficits, namely a phonological deficit in the case of dyslexia and a deficit in the number module in the case of dyscalculia. In four groups of 8- to 10-year-olds (42 control, 21 dyslexic, 20 dyscalculic, and 26 dyslexic/dyscalculic), phonological awareness, phonological and visual–spatial short-term and working memory, naming speed, and basic number processing skills were assessed. A phonological deficit was found for both dyslexic groups, irrespective of additional arithmetic deficits, but not for the dyscalculia-only group. In contrast, deficits in processing of symbolic and nonsymbolic magnitudes were observed in both groups of dyscalculic children, irrespective of additional reading difficulties, but not in the dyslexia-only group. Cognitive deficits in the comorbid dyslexia/dyscalculia group were additive; that is, they resulted from the combination of two learning disorders. These findings suggest that dyslexia and dyscalculia have separable cognitive profiles, namely a phonological deficit in the case of dyslexia and a deficient number module in the case of dyscalculia.
Keywords: Dyslexia; Dyscalculia; Phonological deficits; Number module; Magnitude comparison; Mental number line
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