Verbal coding deficits in learning-disabled readers: A multiple stage model

Abstract

This article reviews some selected literature, drawn from the last 10 years, suggesting that learning-disabled (LD) The present article is directed at the question of how information is integrated in the minds of skilled and learning-disabled (LD) readers as a function of diverse coding schemes, particularly for pictures and words. An important aim of this review is to bring the role of verbal coding and individual differences in reading under a flexible theoretical framework. The favored view is that information from verbal and visual sources is predominantly represented in a semantic (conceptual) form for skilled readers and a modality-specific visual form for LD readers. A three-stage model

Word length, phonemic, and visual similarity effects in poor and normal readers

“…These memory deficits therefore appear to be specific to verbal, but not visual, short-term memory processes (Swanson, 1984;Vellutino, 1979;Vellutino & Scanlon, 1987). Thus, what is known about dyslexia and its relationship to speech and language difficulties appears to be consistent with a phonological (verbal coding) deficit hypothesis; poor readers encounter difficulty when visual stimuli have to be named (Swanson, 1987;Vellutino, 1977Vellutino, , 1979.…”

“…Verbal labels are activated by the presentation of a visual stimulus, and conversely the presentation of an auditory stimulus is said to elicit its corresponding visual form (Swanson, 1987). There is evidence that poor readers lack automaticity in retrieving verbal labels, since they have slower speech onset than chronological-age controls when labeling singly presented pictures (Johnston & Anderson, 1998), performance generally being RA appropriate.…”

“…Thus although poor readers are ca-pable of verbally labeling pictorial stimuli, it is effortful, and such difficulties may lead to immature rehearsal strategies that do not allow adequate opportunity to verbally synthesize or "chunk" information for effective storage and retrieval (Torgesen & Goldman, 1977;Vellutino, 1977). If poor readers' verbal and visual coding systems are poorly connected (Swanson, 1987), or if they do not integrate these codes for efficient storage and/or retrieval of visual information (e.g., Vellutino, 1979), this may bias them to rely more on visual processing (Nelson & Brooks, 1973;Swanson, 1987). In the face of inefficient phonological processing skill, poor readers may similarly be more or less forced to rely on intact visual processes to compensate for phonological impairments.…”

Processing Abilities Associated with Phonologic and Orthographic Skills in Adult Learning Disability

“…Specifically, short-term/working memory ability and visual processing ability were associated with reading problems whether orthographic or phonologic deficits were present. As suggested by past studies (e.g., Swanson 1989) and shown in the current results, short-term/working memory deficits generally relate to reading skill and contribute unique variance above and beyond general intelligence in explaining both phonologic and orthographic processes in reading. Similarly, visual processing ability contributes unique variance in explaining both phonologic and orthographic processes in reading even when accounting for the contribution of general intelligence.…”

“…Furthermore, it has been shown that automatic visual-orthographic skills become more associated with reading comprehension over time (Perfetti, 1985). In addition to the importance of phonologic and orthographic skills, several researchers have demonstrated the importance of short-term memory and working memory to reading (Evans, et al 2002;Mann & Lieberman, 1984;Swanson, 1989).…”