01 NRDC Dyslexia 1-88 update - Texthelp

Developmental dyslexia in adults: a research review 59
With respect to adult ‘ordinary’ poor readers, who do not have a naming-speed deficit, there
is evidence that fluency can be taught and that developing fluency can sometimes lead to
increases in reading achievement (Kruidenier, 2002). However, whether a core deficit in visual
naming speed will prove as amenable to treatment as a phonological deficit has not been
thoroughly investigated (Lovett et al., 2000b). While intensive phonological interventions have
led to improvements in reading accuracy, they have had little effect on fluency (Torgesen et
al., 2001). However, there are indications that, at least for interventions involving children,
teaching programmes can be designed to enhance fluency in participants with naming-speed
impairments (Lovett et al., 2000a; Wolf et al., 2000b).
There is evidence that interventions can enhance fluency in adult ordinary poor readers.
We do not know yet if interventions can enhance reading fluency in dyslexic adults.
Limitations of the double-deficit hypothesis
The double-deficit hypothesis ‘has never been conceptualised as a total explanation of
dyslexia’ (Wolf & Bowers, 1999). Like the phonological deficit hypothesis, it does not address
all the problems experienced by some persistently poor readers. Meanwhile, conflicts of
evidence as to the independence of naming-speed deficits from phonemic awareness deficits
have yet to be resolved. The appearance of independence has been attributed to failure to
control for letter-knowledge (de Jong & van der Leij, 1999), while the greater severity of
impairment associated with a double deficit has been attributed in part to a statistical artefact
caused by grouping children based on their performance on two correlated continuous
variables, at least as far as some poor readers are concerned (Schatschneider et al., 2002).
Opinions differ widely as to the proportion of dyslexic people with a reading rate deficit, a
difference that may reflect variation in the methods used to identify research samples. It may
also be the case that differences between groups are invalid at the level of the individual: in
one study, when individual participants were investigated, it was found that approximately
53 per cent of the dyslexic poor readers and 42 per cent of ‘ordinary’ poor readers had
reaction times equal to or faster than those of the good readers (Catts et al., 2002). This
finding might or might not be replicated; until the question is decided, we must suspend our
judgement.
We are not yet in a position to assess the usefulness of the double-deficit hypothesis in
explaining dyslexia.
Dyslexia and automaticity: the cerebellar deficit hypothesis
Introduction
Reading is a complex skill (Carr et al., 1990). When we read a single word, our brains make
separate computations sustained by distinct neural areas, involving visual integration of the
word, access to its phonological code, access to its semantic meaning, access to the structural
form of the object that it represents (where that is applicable) and access to its learned output
(Posner et al., 1997). If each of these component processes required attention, our attentional
capacity would soon be overwhelmed (LaBerge & Samuels, 1974); decoding would then
become laboriously slow and we would have little if any attentional capacity left for