01 NRDC Dyslexia 1-88 update - Texthelp

Developmental dyslexia in adults: a research review 21
appears to be no support for the belief that either dyslexics or ordinary poor readers are overrepresented
in prison populations. It follows that, as careful investigations have shown, the
correlation between low literacy and offending does not indicate a causal relationship
(Farrington, 1998; Fergusson & Lynskey, 1997; Flood-Page et al., 2000; Gottfredson, 2001;
Maguin et al., 1993; and see Malmgren et al., 1999; Maughan et al., 1996; Smart et al., 2001).
The topic of screening and its implications for the determination of prevalence, is discussed in
Appendix 8.
Prevalence estimates for dyslexia are arbitrary and may owe more to politics than to science.
High estimates of the prevalence of dyslexia in prisons are inflated by the inclusion of
‘ordinary poor readers’ and are likely to be gross over-estimates.
Research issues
Four issues in dyslexia research follow directly from the conceptual issues.
1. Choosing the concept
The first issue concerns the concept itself. The choice of concept may or may not be reflected
in the term chosen to identify it, whether it is ‘dyslexia’, ‘specific reading retardation’, ‘reading
disability’, ‘unexpected reading difficulty’, ‘learning disability’, or even ‘low literacy’. The
concepts have varying degrees of overlap and entail different causal assumptions (or none at
all), although it is not always the case that the causal assumptions reflect those implied by
the chosen term. ‘Dyslexia’, for example, implies a biological cause (see Appendix 1),
although this is not always clear from the way in which the term is used. By contrast, while
‘reading disability’ and ‘specific reading retardation’ embrace ‘dyslexia’ they are concepts that
do not embody any causal assumptions.
Unlike the concepts of ‘reading disability’ and ‘specific reading retardation’, the concept of
‘dyslexia’ embodies a causal theory—namely, that the origin of the difficulty is biological.
2. Making the concept a reality
The second issue concerns the method by which the chosen concept is applied in practice (or
‘operationalised’). Practitioners and researchers have employed a number of methods to
identify their target group for intervention or comparison:
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The simplest method is possibly age-discrepant performance on a standard attainment test.
An alternative is IQ-discrepant performance on a standard attainment test, sometimes but not
always adjusted by a regression formula. (Either or both of these methods, used informally,
will prompt referral for assessment in everyday life. However, it needs to be recognised that a
statistically significant difference between two groups does not necessarily imply that the
difference between them is categorical; it may only be a matter of degree.)
A third course is the use of a behavioural screening instrument, sometimes but not always
followed up with an educational psychologist’s assessment using a psychometric test battery
with an intelligence scale.
A fourth course is to determine a discrepancy between reading comprehension and listening
comprehension.