Eye Movements and Dyslexia

BU’s Dr Julie Kirkby is researching eye-movements during reading, to better understand childhood dyslexia.

Dyslexia is a common developmental disorder, affecting the reading ability of 100 children in 1000, but there is considerable disagreement over its neurological and cognitive basis.

Using state-of-the-art eye movement recording, Dr Kirkby and her team are conducting experiments to determine the precise link between dyslexia and the integrated activity of the left and right eye (binocular coordination).

One major theory of dyslexia, Magnocellular Theory (MCT), offers a neurological account of the disorder. MCT postulates that deficient functioning of the magnocellular stream of visual system reduces both visual contrast sensitivity and binocular coordination. Although such deficits are plausible, and would impact negatively on a child’s ability to read, MCT has been subject to relatively little empirical evaluation. It is surprising that, despite limited convincing evidence that the proposed underlying deficit exists, intervention programs have been developed that focus primarily on improving binocular coordination (e.g., Stein, Richardson, & Fowler, 2000).

For this reason, a thorough evaluation of MCT in relation to dyslexia is overdue. In fact, recent research by Kirkby et al. (2010, 2011, 2013) suggests the link between binocular coordination and dyslexia is questionable. This work showed that some binocular disparity is commonplace amongst both skilled adult and typically developing (TD) child readers, during both reading and non-reading tasks. Moreover, when Kirkby et al. (2011) compared these groups with dyslexic children, they found that dyslexia produced reduced binocular coordination, but only on the reading tasks. A magnocellular account of dyslexia would predict dyslexics would show deficits on both kinds of tasks.