VISUAL AND LANGUAGE PROCESSING DEFICITS ARE CONCURRENT IN DYSLEXIA

Research has demonstrated that dyslexic subjects have language process ing problems. More recent evidence indicates that dyslexic subjects al so suffer a low-level visual information processing deficit. Little ev idence is available to indicate the extent to which dyslexic subjects simultaneously show a visual and language processing dysfunction. In t his study. 35 normal and 35 dyslexic subjects aged from 7.9 to 14 year s of age were compared on three reading process variables, a visual pr ocessing score, a test of phonological coding and a test of language c omprehension, each of which were shown to be related to reading per fo rmance. The visual processing score was the slope of the regression li ne predicting the duration of visible persistence as a function of spa tial frequency. The language processing measures were a test of phonol ogical coding of orthographically legal Non-Words and a test of langua ge comprehension, the Token Test. The results showed that the visual p rocessing score was significantly predictive of group membership with 91% of the dyslexic group and only 20% of the normal readers having lo w scores on this measure. The Non-Word test was found to be a perfect discriminator for dyslexia by indicating that every subject in this gr oup had a major phonological coding deficit. An unexpected finding of the present results was that the Token Test did not discriminate betwe en the groups. The results are interpreted as providing evidence for t he concurrence of visual and language deficits in dyslexia.