Rapid processing of letters, digits and symbols: what purely visual‐attentional deficit in developmental dyslexia?

Abstract

Visual-attentional theories of dyslexia predict deficits for dyslexic children not only for the perception of letter strings but also for non-alphanumeric symbol strings. This prediction was tested in a two-alternative forced-choice paradigm with letters, digits, and symbols. Children with dyslexia showed significant deficits for letter and digit strings but not for symbol strings. This finding is difficult to explain for visual-attentional theories of dyslexia which postulate identical deficits for letters, digits and symbols. Moreover, dyslexics showed normal W-shaped serial position functions for letter and digit strings, which suggests that their deficit is not due to an abnormally small attentional window. Finally, the size of the deficit was identical for letters and digits, which suggests that poor letter perception is not just a consequence of the lack of reading. Together then, our results show that symbols that map onto phonological codes are impaired (i.e. letters and digits), whereas symbols that do not map onto phonological codes are not impaired. This dissociation suggests that impaired symbol-sound mapping rather than impaired visual-attentional processing is the key to understanding dyslexia.

Varieties of developmental dyslexia in Greek children

“…A difference between previous studies and the present one is that multi-character processing was assessed using letter sounds in this study, and not letter names. It has been suggested that a deficit in performance in letter report tasks may not be the result of reduced visual attention span, but is rather due to impaired visual to phonological mapping (Hawelka & Wimmer, 2008;Ziegler et al, 2010), in line with the phonological deficit theory of dyslexia. The letter report task undoubtedly does involve the activation of phonological information, and phonological processing should be in evidence even more when the task involves letter sounds rather than names, however, the interpretation of performance in the task has been that it allows us to assess the ability to process multiple elements in parallel.…”

Does Training in Syllable Recognition Improve Reading Speed? A Computer-Based Trial With Poor Readers From Second and Third Grade

“…First, the RAN-reading association may derive from visual processes like visual pattern recognition and visual discrimination (Araújo et al, 2011;Klein, 2002;Stainthorp, Stuart, Powell, Quinlan, & Garwood, 2010). However, these explanations have not been either widely studied or supported (Di Filippo et al, 2006; Gasperini, Brizzolara, Chritofani, Casalini, & Chilosi, 2014), while the results of deficits in visualattentional processes as a cause of poor reading skill are contradictory (Ger-17 mano, Reilhac, Capellini, & Valdois, 2014;Ziegler, Pech-Georgel, Dufau, & Grainger, 2010). Second, the ability to learn arbitrary sound-symbol associations is involved in both RAN and reading (Manis et al, 1999;Ziegler, Pech-Georgel et al, 2010).…”

“…However, these explanations have not been either widely studied or supported (Di Filippo et al, 2006; Gasperini, Brizzolara, Chritofani, Casalini, & Chilosi, 2014), while the results of deficits in visualattentional processes as a cause of poor reading skill are contradictory (Ger-17 mano, Reilhac, Capellini, & Valdois, 2014;Ziegler, Pech-Georgel, Dufau, & Grainger, 2010). Second, the ability to learn arbitrary sound-symbol associations is involved in both RAN and reading (Manis et al, 1999;Ziegler, Pech-Georgel et al, 2010). Third, both skills require serial processing, a notion that is supported by results showing that continuous RAN is more strongly associated with reading than discrete naming (Badian, 1993; Bowers & Swanson, 1991; Chiappe, Stringer, Siegel, & Stanovich, 2002; de Jong, 2011; Georgiou, Parrila, Cui, & Papadopoulos, 2013;Zoccolotti et al, 2013).…”

Sequential Versus Simultaneous Processing Deficits in Developmental Dyslexia

“…It has however been argued that poor performance in letter report tasks might be due to verbal deficits in encoding and reporting letters, and as such reflected a visual-tophonology code mapping disorder (Ziegler, Pech-Georgel, Dufau, & Grainger, 2010) rather than a visual attention resource limitation. Ziegler et al (2010)'s account is based on data from a forced choice detection task in which children were shown briefly presented strings of letters, digits or symbols. At the offset of the multi-character string, participants had to choose which one of two characters previously occurred in a cued position within the string.…”