Dyslexia and dyscalculia: which neuropsychological processes distinguish the two developmental disorders?

AIMS OF THE STUDY In the developmental neuropsychological literature there is a strong debate about the specific cognitive processes involved in developmental dyslexia and dyscalculia. Moreover, it is still unclear whether the children with both disorders show a neuropsychological profile similar to those with dyslexia, with dyscalculia or the summation of both. METHOD After screening 1572 children from the third, fourth and fifth grades, 186 participants with difficulties in reading and/or calculation and a control group were selected. According to children’s performance in the screening tasks, the selected sample was divided in four groups: 68 dyslexic, 14 dyscalculic, 15 children with dyslexia and dyscalculia in comorbidity, and 89 controls. An experimental battery of tests was administered in order to examine phonological awareness, phonological and visuo-spatial working memory and numeric representation. RESULTS Results are discussed in the context of the hypothesis of the domain-specific cognitive deficit, showing phonological deficits in dyslexic children; number processing and visuo-spatial deficit in dyscalculic children. Children with comorbidity showed additive deficits compared with subjects with pure developmental dyslexia or dyscalculia, due to the summation of deficits in these two developmental disorders.