01 NRDC Dyslexia 1-88 update - Texthelp
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01 NRDC Dyslexia 1-88 update - Texthelp

01 NRDC Dyslexia 1-88 update - Texthelp 01 NRDC Dyslexia 1-88 update - Texthelp

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58 Research Report Naming-speed deficits in other languages There is evidence for a naming-speed deficit across a wide range of writing and spelling systems. It is a specific marker of reading disability in both opaque and transparent orthographies and in the presence or absence of attentional problems (Närhi & Ahonen, 1995). It appears in non-alphabetic systems such as Chinese, where beginning readers have naming-speed deficits and phonological memory deficits like their alphabetic counterparts (Ho & Lai, 1999). Significantly, in spelling systems such as German where there is little evidence of a phonological awareness deficit, dyslexics (i.e. dysfluent readers) exhibit a substantial naming-speed (or perhaps phonological processing) deficit (Wimmer et al., 2000). This distinction may be critically important for reading difficulties in English, too. Naming-speed impairments appear to be a universal marker of reading disability, irrespective of writing and spelling systems. The relation of naming-speed to psychometric and demographic variables There is an interesting dissociation between good and poor readers when the relationships between speeded naming and other variables are compared. For poor readers in general, both naming speed and phonological awareness may be significantly associated with word reading, but verbal intelligence appears to have no association with it; in contrast, for good readers, phonological awareness and verbal intelligence, but not naming speed, may be significantly associated with word reading (McBride-Chang & Manis, 1996). In all such comparisons, it has been suggested that attention should be paid to these variables when interpreting test scores: IQ and SES; differences in the variability of predictors over time; the quality and type of reading instruction; and the different rates of change of predictors at different ages (Wolf & Bowers, 1999). The prognostic significance of naming-speed deficits in dyslexia While some processes are believed to be innate and thus not amenable to training, motivation or arousal, others need practice before they become rapid, parallel and automatic; in contrast, effortful mental processes are slow, serial and subjectively controlled (August & Garfinkel, 1990). The exercise of a complex skill requires the co-ordination of many component processes within a brief time-frame; if each one required attention, then the exercise would become impossible because it would exceed attentional capacity (LaBerge & Samuels, 1974). Fluent reading therefore requires that word recognition is automatised in order to free learners’ attentional capacity for comprehension, which cannot be automatised in the same way (Fuchs et al., 2001). Most readers attain a sufficient level of automaticity in word recognition to be able to concentrate on meaning. The critical question is whether all readers can do so or whether some people can learn how the alphabetic system works but then cannot apply that knowledge without effortful subjective control. It has been suggested that readers with naming-speed and double deficits constitute some of the treatment-resisters described in intervention studies aimed at enhancing phonological awareness (Wolf & Bowers, 2000). Evidence from studies of dyslexics in higher education lends weight to this suggestion; although dyslexic university students may have developed sufficient compensation skills to attain average scores on untimed reading achievement measures, they may continue to demonstrate significant difficulty in rapid naming (Riccio et al., 1998).

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

58<br />

Research Report<br />

Naming-speed deficits in other languages<br />

There is evidence for a naming-speed deficit across a wide range of writing and spelling<br />

systems. It is a specific marker of reading disability in both opaque and transparent<br />

orthographies and in the presence or absence of attentional problems (Närhi & Ahonen,<br />

1995). It appears in non-alphabetic systems such as Chinese, where beginning readers have<br />

naming-speed deficits and phonological memory deficits like their alphabetic counterparts<br />

(Ho & Lai, 1999). Significantly, in spelling systems such as German where there is little<br />

evidence of a phonological awareness deficit, dyslexics (i.e. dysfluent readers) exhibit a<br />

substantial naming-speed (or perhaps phonological processing) deficit (Wimmer et al., 2000).<br />

This distinction may be critically important for reading difficulties in English, too.<br />

Naming-speed impairments appear to be a universal marker of reading disability,<br />

irrespective of writing and spelling systems.<br />

The relation of naming-speed to psychometric and demographic variables<br />

There is an interesting dissociation between good and poor readers when the relationships<br />

between speeded naming and other variables are compared. For poor readers in general,<br />

both naming speed and phonological awareness may be significantly associated with word<br />

reading, but verbal intelligence appears to have no association with it; in contrast, for good<br />

readers, phonological awareness and verbal intelligence, but not naming speed, may be<br />

significantly associated with word reading (McBride-Chang & Manis, 1996).<br />

In all such comparisons, it has been suggested that attention should be paid to these<br />

variables when interpreting test scores: IQ and SES; differences in the variability of predictors<br />

over time; the quality and type of reading instruction; and the different rates of change of<br />

predictors at different ages (Wolf & Bowers, 1999).<br />

The prognostic significance of naming-speed deficits in dyslexia<br />

While some processes are believed to be innate and thus not amenable to training, motivation<br />

or arousal, others need practice before they become rapid, parallel and automatic; in<br />

contrast, effortful mental processes are slow, serial and subjectively controlled (August &<br />

Garfinkel, 1990). The exercise of a complex skill requires the co-ordination of many<br />

component processes within a brief time-frame; if each one required attention, then the<br />

exercise would become impossible because it would exceed attentional capacity (LaBerge &<br />

Samuels, 1974). Fluent reading therefore requires that word recognition is automatised in<br />

order to free learners’ attentional capacity for comprehension, which cannot be automatised<br />

in the same way (Fuchs et al., 20<strong>01</strong>). Most readers attain a sufficient level of automaticity in<br />

word recognition to be able to concentrate on meaning. The critical question is whether all<br />

readers can do so or whether some people can learn how the alphabetic system works but<br />

then cannot apply that knowledge without effortful subjective control.<br />

It has been suggested that readers with naming-speed and double deficits constitute some of<br />

the treatment-resisters described in intervention studies aimed at enhancing phonological<br />

awareness (Wolf & Bowers, 2000). Evidence from studies of dyslexics in higher education<br />

lends weight to this suggestion; although dyslexic university students may have developed<br />

sufficient compensation skills to attain average scores on untimed reading achievement<br />

measures, they may continue to demonstrate significant difficulty in rapid naming (Riccio et<br />

al., 1998).

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