Chapter

The Visual Nature of the Visual Attention Span Disorder in Developmental Dyslexia

Sylviane Valdois, Delphine Lassus-Sangosse and Muriel Lobier

in Visual Aspects of Dyslexia

Published in print August 2012 | ISBN: 9780199589814
Published online September 2012 | e-ISBN: 9780191744785 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780199589814.003.0007
The Visual Nature of the Visual Attention Span Disorder in Developmental Dyslexia

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Developmental dyslexia is widely thought to result from a core phonological disorder. However, evidence has been provided for poor visual parallel processing of letter strings in a subset of dyslexic individuals. This disorder has been interpreted as reflecting a reduced span of visual attention, i.e., a reduction of the visual attention resources that can be allocated to multiple elements in a visual display. Hence poor processing of letter strings has been attributed to defective visual processing skills. But some have argued that poor performance on these tasks could be the result, rather than the cause, of a phonological disorder. This chapter first introduces the concept of the visual attention span and provide a theoretical account of its role in reading acquisition and skilled reading. It then reviews evidence that poor performance in letter report tasks cannot be interpreted as phonological. Dyslexic children who can only report a few letters from a briefly presented 5-consonant string have no problem reporting their names when the letters are displayed one after the other. Thus, their disorder is specific to visual parallel processing and is not sensitive to the load on verbal short-term memory of the task. Further, these children show a similarly poor performance whether the global report task is performed alone or associated with a concurrent counting task that taxes phonological memory and prevents online verbal encoding during processing. It follows that poor performance on this task is not modulated by verbal encoding skills. Additional evidence comes from recent findings showing that children with poor performance in letter report also perform poorly in categorical tasks that use non-verbal stimuli but similarly require visual parallel processing. These latter findings show that in developmental dyslexia reduced visual attention span extends to non-verbal tasks, ruling out phonological accounts of this disorder.

Keywords: phonological; visual; letter; encoding; developmental

Chapter.  5107 words.  Illustrated.

Subjects: Neuroscience

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