Similarities Between Acquired Dyslexia, Developmental Dyslexia and Early Reading

King, Bernardine (2006). Similarities Between Acquired Dyslexia, Developmental Dyslexia and Early Reading. PhD thesis The Open University.



This thesis compared responses to onsets and offsets of stimuli (visual, auditory, phonemic and orthographic) in children with developmental dyslexia (DDs), adults with acquired dyslexia (ADs) and early readers (ERs). Similarities were observed between the reading characteristics of ERs who demonstrated an incomplete mapping between letters and sounds and a group of ADs. Cluster analysis identified children of 'low', 'intermediate' (IRs) and 'high' alphabetic ability in two samples of early readers (4 to 6-year-olds). IRs showed an alphabetic profile similar to those expected of Ehri's (1995) partial alphabetic phase. There was a lack of discrimination between auditory onset and offset in IRs, DDs and ADs that suggested a basis for problems in establishing reliable phonological representations. DDs showed deficits in sensitivity to the first of contiguous trios of tones and of phonemes, and to the last in a series of three lights, compared to chronological age controls (CAs). DDs were similar to RAs (reading age controls) on most tasks. ADs were slower and less accurate in temporal processing tasks than their CAs but showed similarities to their RAs. This supports the notion of a cognitive delay in developmental dyslexia and a regression to an immature cognitive state in acquired dyslexia. Cluster analysis of ERs, ADs and DDs on alphabetic measures demonstrated that, whereas many of the DDs (10/22) were able to progress to a more advanced phase of reading, most (8/9) ADs clustered with the IRs, suggesting that many ADs may be trapped within a cognitive state comparable to Ehri's partial alphabetic phase. A cognitive model of both acquired and developmental dyslexia is proposed whereby, despite different biological causes for the two conditions, a failure to fully complete alphabetic links due to the dominance of the whole-word level of representation may form the basis of both dyslexias.

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