Specific Disorders and Broader Phenotypes: The Case of Dyslexia

Abstract

Two studies investigating the cognitive phenotype of dyslexia are described. Study 1 compared three groups of English and Italian children on speed of processing tasks: (a) children with dyslexia, (b) generally delayed poor readers and (c) CA-controls. In tests of simple and choice reaction time and two visual scanning tasks, children with dyslexia performed like controls and significantly faster than generally delayed poor readers. A second prospective longitudinal investigation of children at family risk of dyslexia showed that problems of literacy development were less circumscribed, with affected children showing phonological deficits in the context of more general oral language difficulties. An important finding was that the risk of dyslexia was continuous in this sample; among at-risk children with normal literacy development, mild impairments of phonological skills were apparent early in development, and subtle difficulties with reading fluency and spelling emerged in early adolescence. A case series extended these findings to show that phonological deficits alone are insufficient to explain literacy difficulties, and it is children with multiple deficits (including language problems) that are more likely to succumb to reading failure.

Phonological Awareness and Working Memory in Arabic-Speaking Egyptian Preschool Children at Risk for Dyslexia

“…It is very important for a word to be segmented into phonemes in order for a child to hold it temporarily in WM until it can be analyzed. If an individual cannot hold an unfamiliar word in one's short-term memory long enough to repeat it, segmenting the word poses an immediate challenge (Nicolson et al, 1992 Price, Frith, & Frith, 1999;Hansen & Bowey, 1994;McDougall & Donohoe, 2002;Palmer, 2000;Pennington et al, 2001;Plaza, Cohen, & Chevrie-Mulleret, 2002;Roodenrys & Stokes, 2001;Smith-Spark & Fisk, 2007;Smith-Spark, Fisk, Fawcett, & Nicholson, 2003;Snowling, 2008;Stanovich, Siegel, & Gottardo, 1997;Swanson, 1994). These difficulties influence reading acquisition, reading ability, text comprehension and classroom functioning (Alloway & Gathercole, 2006).…”

When words fail us: insights into language processing from developmental and acquired disorders

“…R. Soc. B 369: 20120403 phonological deficit [64] and how it interacts with other factors to predict outcome [71]. Also, as noted above, the strength of this relationship may depend on the phonological task employed [5].…”

The Role of Phonological Awareness and Rapid Automatized Naming in the Prediction of Reading Difficulties in Portuguese

“…Despite its prominent position in the literature, the phonological defi cit model has recently become the subject of increasing scrutiny (Snowling, 2008). In particular, it has been suggested that phonological processing defi cits are not suffi cient (e.g., Pennington, 2006;Snowling, 2008) or even necessary (e.g., Pennington, 2006;Wolf & Bowers, 1999) for diffi culties in learning to read to occur.…”

“…In particular, it has been suggested that phonological processing defi cits are not suffi cient (e.g., Pennington, 2006;Snowling, 2008) or even necessary (e.g., Pennington, 2006;Wolf & Bowers, 1999) for diffi culties in learning to read to occur. For example, Snowling, Gallagher and Frith (2003) have noted that, notwithstanding their diffi culties in phonological awareness tasks, not all children at high familial risk of developmental dyslexia present with diffi culties in learning to read.…”