Thursday, September 29, 2016

Dyslexia: a deficit in visuospatial attention, not in phonological processing.

Dyslexia is a specific reading disability that affects 5-10% of the population. Phonological deficits, or difficulties relating speech sounds to letter forms, have been linked to the reading difficulties experienced by children with dyslexia. Although a large body of research on dyslexia has focused on phonological awareness and the reading difficulties it can cause, this review focused on an alternative possibility. The authors argued that poor visual-spatial attention might be the cause of reading problems, including phonological impairments, in children with dyslexia.

One of the common difficulties reported for children with dyslexia is the misordering of letters, or an ambiguity regarding the sequence of letters in words, and such difficulties cannot be explained by phonological deficits. Learning to read requires the training of a cognitive mechanism referred to here as the ‘spotlight of attention’; this mechanism helps readers recognize one item at a time by shifting attention across the letters of a word. The authors suggested that difficulties with this visuospatial attention mechanism in children with dyslexia might affect their reading development. Indeed, several studies have reported poor visuospatial attention in children with dyslexia (Casco &Prunetti, 1996; Facoetti et al., 2000; Hari et al., 1999).

To further support the idea that poor phonological awareness may not be the cause of the reading difficulties experienced by children with dyslexia, the authors presented evidence that the development of phonological awareness itself is affected by deficits in the visual system. That is, the development of phonological awareness is dependent on normal orthographic input that facilitates standard visual processing, such as grapheme identification and the translation of graphemes into phonemes. Based on the possibility of a poor visual system in children with dyslexia, the authors suggested that future research should investigate this question and potential interventions in children with dyslexia.

Areej Balilah, PhD Candidate with Dr. Lisa Archibald