Developmental dyslexia: The visual attention span deficit hypothesis

Abstract

The visual attention (VA) span is defined as the amount of distinct visual elements which can be processed in parallel in a multi-element array. Both recent empirical data and theoretical accounts suggest that a VA span deficit might contribute to developmental dyslexia, independently of a phonological disorder. In this study, this hypothesis was assessed in two large samples of French and British dyslexic children whose performance was compared to that of chronological-age matched control children. Results of the French study show that the VA span capacities account for a substantial amount of unique variance in reading, as do phonological skills. The British study replicates this finding and further reveals that the contribution of the VA span to reading performance remains even after controlling IQ, verbal fluency, vocabulary and single letter identification skills, in addition to phoneme awareness. In both studies, most dyslexic children exhibit a selective phonological or VA span disorder. Overall, these findings support a multi-factorial view of developmental dyslexia. In many cases, developmental reading disorders do not seem to be due to phonological disorders. We propose that a VA span deficit is a likely alternative underlying cognitive deficit in dyslexia.

Varieties of developmental dyslexia in Greek children

“…The present findings support the hypothesis that postulates that a multi-character simultaneous processing deficit will hamper the processing of larger graphemic units, that is necessary to build up the lexical store during the course of literacy acquisition. Instead the child will be forced to rely on slow, serial processing (Ans et al, 1993;Bosse et al, 2007). As noted in the Introduction, the association of surface dyslexia and letter report difficulty has been reported before Dubois et al, 2010;Peyrin et al, 2012).…”

Sequential Versus Simultaneous Processing Deficits in Developmental Dyslexia

“…The visual attention span (VA Span hereafter) hypothesis put forward by Bosse, Tainturier and Valdois (2007) is complementary to the phonological deficit hypothesis. It posits that another cause of developmental dyslexia stands in a limitation of the visual attention resources that can be allocated simultaneously to letters within words.…”

“…Following this theoretical framework, it was reasoned that a VA Span reduction (i.e., a reduction of the number of visual letters that can be processed simultaneously) should prevent normal encoding of the orthographic sequence of most words (Bosse et al, 2007). According to this idea, a reduced VA Span would be particularly detrimental when reading irregular words that cannot be accurately decoded serially.…”

Visual attention span deficits and assessing causality in developmental dyslexia

“…http://dx.doi. org/10.1038/nrn3836-c1 (2015)) 2 , Lobier and Valdois bring together 12 of their studies to argue that a visual attention (VA) span deficit meets the criteria that are required to demonstrate causality in developmental dyslexia [3][4][5][6][7][8][9][10][11][12][13][14] . Unfortunately, all of the studies that were discussed used letters to assess VA span; thus, the demonstrated deficit only affects letters and is causally ambiguous , as the individuals with dyslexia and control individuals that were studied differed dramatically in their experience of recoding letters to sound.…”