01 NRDC Dyslexia 1-88 update - Texthelp

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Research Report
which may normally act as an anatomical bridge between Broca’s area, the superior temporal
cortex, and the inferior parietal cortex (Paulesu et al., 1996). How this might occur is unclear;
in the light of current knowledge, it is unlikely that it occurs at all (Lieberman, 2000).
Further research is indicated, because of the possibility that specific explanations, even if they
do not apply to every instance, might lead to specific interventions. However, any search for a
single neural substrate of dyslexia may be misguided if, when the term ‘dyslexia’ is used to
denote an otherwise inexplicably severe and persistent difficulty in learning to read, it is
understood as a symptom—or a ‘final common pathway’—of more than one cause of
developmental abnormality in the neural system.
According to phonological deficit theory, dyslexic people are specifically impaired in their
ability to detect and process speech sounds.
The phonological deficit theory is a cognitive theory, which assumes a biological explanation
but does not propose one specifically.
What does the phonological deficit theory explain?
The phonological deficit theory has been described as a ‘near-complete explanation of the
problems dyslexic children face when learning to read’ (Fawcett & Nicolson, 1994). For this
and other reasons, it became ‘the consensus view of most dyslexia researchers’ about
15 years ago (Nicolson, 1996). Within the domain of reading, the phonological deficit theory
accounts for dyslexics’ poor performances in short-term memory, long-term memory, picture
naming and verbal repetition, all of which are consistent with a deficiency in the use of
phonologically-based information (Rack, 1994).
However, the description ‘near-complete’ is circumspect in acknowledging that the
phonological deficit theory may not account for all of the difficulties that dyslexic people
experience in their efforts to become literate. The description is also circumspect in implying
that dyslexic people may experience difficulties unrelated to literacy and which, for some, may
cause more distress than is caused by their failure to achieve functional literacy.
The phonological deficit theory offers an explanation of problems with accurate and fluent
recall of phonologically-coded items in memory.
What does the phonological deficit theory not explain?
While providing a persuasive account of difficulties in reading, the phonological deficit theory
predicts problems with only the phonological aspects of spelling and makes no predictions
about the motor skill problems of handwriting (Nicolson, 1996).
With respect to spelling, the phonological deficit hypothesis has been understood to predict
that poor readers will compensate for phonological deficits by relying heavily on their visual
memorisation of orthographic patterns. Such students should produce a low proportion of
spellings revealing sensitivity to phonological structure relative to the proportion of their
spellings revealing sensitivity to orthographic structure (Bourassa & Treiman, 2001). Dyslexic
people and non-dyslexic people may be statistically indistinguishable in terms of correct
spellings of real words, performing at similar levels on measures designed to tap the
phonological and orthographic processes involved in spelling (Bourassa & Treiman, 2003).