Inter- versus intra-hemispheric learning in dyslexic and normal readers

The present study investigated the hypothesis that developmental dyslexia is attributable to dysfunction in inter-hemispheric transfer. Dyslexic and normal readers in second grade (age-range seven to eight years) and sixth grade (11 to 12 years) were given tachistoscopic presentations of novel visual stimuli (Chinese ideographs), randomly presented to the left and right visual fields and to the central fixation point. Each stimulus was paired with a common English word (spoken) and the children were asked to associate the two. The transmission deficit hypothesis predicts that poor and normal readers will be differentiated in the case of presentations to the right hemisphere (left visual field) but will not differ significantly in the case of presentations to the left hemisphere (right visual field). This hypothesis was not supported. Normal readers at both grade levels performed significantly better than poor readers in both visual-field presentations.