01 NRDC Dyslexia 1-88 update - Texthelp

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Research Report
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A fifth course is to undertake differential diagnosis by exclusionary conditions, so that the
target group consists of people whose poor reading skills cannot otherwise be explained.
A sixth course is to identify the target group by neurological soft signs and associated
characteristics, whether or not those ‘signs’ only co-occur with poor reading.
A seventh course is effectively to delegate the selection in some way, by identifying the target
group on the basis of attendance at some form of special education or at a clinic.
An eighth course is to carry out a programme of ‘conventional’ (i.e. explicit and systematic)
instruction in the alphabetic principle with an undifferentiated group of poor readers and to
identify the ‘treatment-resisters’ as the true dyslexics on the ground that response to
‘conventional’ instruction fails to meet one of the exclusionary criteria and thus identifies the
treatment-responder as a ‘false positive’.
None of these methods is problem-free. For example, the choice of cut-point on a
dimensional scale needs to be guided by norms, but opinions may differ as to whether those
norms should be for the entire country, for the institution attended by the test-taker, or for
the test-taker’s social background and opportunities (Alexander & Martin, 2000). With IQachievement
discrepancy as with age-discrepancy, the choice of cut-point is largely arbitrary.
No cut-point on any continuum serves to demarcate causal explanations. While a person’s
learning need may be reflected by the severity of their difficulty, there is no clear relationship
between the cause of a reading difficulty and its severity and neither is there a clear
relationship between the severity of difficulty and the prospect of successful learning.
Many researchers would agree with the conclusion that ‘the concept of discrepancy
operationalised using IQ scores does not produce a unique subgroup of children with [reading
difficulty] when a chronological age design is used; rather, it simply provides an arbitrary
subdivision of the reading-IQ distribution that is fraught with statistical and other
interpretative problems’ (Fletcher et al., 1994). Perhaps the most important objection to using
IQ may be that it is a combined measure of both innate and acquired ability, not a measure of
purely innate ability (Ceci, 1991; Mackintosh, 1998); it is necessarily affected by any
neurological defect involved in a learning problem (Rie, 1987).
The problems of quantitative approaches to identifying the target group are not resolved by
qualitative methods of identification using behavioural correlates or ‘signs’ of dyslexia. Among
the problems here are the difficulty in establishing which, if any, of a number of correlates
may be causal and what (given a causal relationship) is the main direction of causality. ‘Soft
signs’, in particular, are found in some people without learning problems and absent in others
who experience learning difficulties; a moderate number of minor ‘signs’ is quite compatible
with normality. Some ‘soft signs’ point in more than one direction; they may indicate a lack of
motor learning, rather than any inability to learn. They are as likely to indicate the
exclusionary conditions normally eliminated by differential diagnosis as they are to indicate
dyslexia.
However, the point at issue is not the validity of any of these identification techniques but
their variety. This variety has implications for the research literature; even where researchers
use the same conceptual term, it cannot be assumed that they have understood it in the same
way. (Appendix 3 shows that variety may be the rule here, too.) Less obvious, but no less
important, is the variety of ways in which the concepts have been operationalised; for
example, the same causal explanation is not necessarily valid for all scores in the lowest
range of any dimensional test. If assumptions like these are questionable in research
involving children, they are much more questionable in research involving adults.