Diagnosing Dyslexia

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Science  02 Dec 2011:
Vol. 334, Issue 6060, pp. 1184
DOI: 10.1126/science.334.6060.1184-a

Dyslexia has often been diagnosed as an unexpectedly poor, or “discrepant” reading level as compared to the tested IQ of the student. This approach generates a bias that tends to attribute poor reading in students with lower IQs to factors other than dyslexia. Using functional MRI (fMRI), Tanaka et al. analyzed phonological processing in 8- to 17-year-old children with poor reading ability, with either normal or low IQ. The imaging for phonological processing in children with IQ discrepant with reading skills reflected the atypical brain function. Children with low IQ and poor reading skills—the nondiscrepant group—also showed brain function patterns similar to those characterizing dyslexia. Thus, the underlying brain function that leads to dyslexia can affect persons with low IQ just as it can those with higher IQ. The results suggest that diagnostic criteria for dyslexia should be revised and that interventions to improve reading skills may benefit a new group, children for whom every cognitive improvement could help.

Psychol. Sci. 22, 1442 (2011).

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