Low-level Visual Processing Skills of Adults and Children with Dyslexia

Previous work by Lovegrove and colleagues (Lovegrove, Martin, & Slaghuis, 1986) suggested that dyslexic children show visual deficits specific to transient processing. We designed and examined a number of threshold and suprathreshold tasks to test the generality of their claims. We first compared the performance of adult dyslexics and child dyslexics to the performance of age-matched normal readers on a series of threshold flicker tasks. In contrast to the earlier results, dyslexics and normal readers did not differ in their contrast thresholds for flickering sinewave gratings. Dyslexic children and normal readers also showed similar performance on two suprathreshold visual search tasks that evaluated transient processing. The evidence suggests that a transient processing deficit is not a general characteristic of developmental dyslexia. Claims that visual factors play a role in dyslexia must address the confounding role of performance and attentional factors.