01 NRDC Dyslexia 1-88 update - Texthelp

52
Research Report
the ‘normal’ readers on this task (Jorm et al., 1986a). If this is also the case with adults, then
it might be that pseudoword repetition does have a discriminant function albeit, paradoxically,
that errors in pseudoword repetition might identify not developmental dyslexics but ‘ordinary’
poor readers—perhaps because the task loads on verbal ability at least as much as it loads
on phonemic discrimination and verbal short-term memory.
Comparable findings have been obtained in studies using other phonological awareness
tasks. Here, too, previous experience of literacy appears to be an important condition for
success, in that otherwise unimpaired but illiterate adults perform very poorly at the task of
phoneme deletion (Adrián et al., 1995)—for example, saying ‘boat’ without the /b/. More
specifically, as a predictor of success, previous experience of alphabetic literacy is better than
previous experience of nonalphabetic literacy (Cheung et al., 2001).
Thus, while phonological awareness tasks are essential to help the adult tutor to plan a
programme of teaching, a student’s initial difficulty with these tasks need not indicate any
biological abnormality since the ability to manipulate speech sounds is a taught skill, not an
outcome of cognitive maturation or exposure to language (Read et al., 1987). Tasks such as
phoneme deletion differentiate poor or beginning readers from accomplished readers; they do
not differentiate dyslexic from non-dyslexic poor readers.
This discussion leads to an important issue in the logic of diagnosis. It may be true —although
the assumption has been queried (Miles et al., 2003)—that everyone with dyslexia experiences
difficulty on assessments of phonological processing. However, the inference that everyone
with impairments in phonological processing must then be dyslexic is not a logical corollary.
The error is a classic one: the deductive fallacy of ‘affirming the consequent’. It is a fallacy
which amateur (and professional) diagnosticians need to recognise and avoid—although that
may prove difficult, since affirming the consequent is implicit in diagnostic materials
published by the Prison Service (HM Prison Service, 1999) and the Basic Skills Agency (Klein,
1993) in the past and it reappears in the Agency’s new Skills for Life Diagnostic Assessments
in Literacy (Bradshaw et al., 2002).
One way of avoiding this fallacy might be to ensure that only those impairments which are
‘persistent’ after years of regular schooling qualify for consideration as ‘dyslexic’ (Herrington
& Hunter-Carsch, 2001). How the tutor manages this situation needs to be guided by its
ethical implications. Moreover, with respect to method and quality of early reading teaching
strategies, the quest to identify whether or not there has been ‘regular schooling’ may be a
fool’s errand.
Phonological deficits do not permit dyslexics to be differentiated from other poor readers.
Limitations of the phonological deficit theory: the phonological-core variable-difference
model of reading disability
The ability to detect and process speech sounds can be compromised for more than one
reason and those reasons are likely to differ from one learner to another. In some cases, the
dominant factor might appear to be experiential; in some, the dominant factor might appear
to be biological; and, in the remaining cases, neither factor might predominate. The question
then arises whether cases of reading disability form discrete clusters (or subtypes). From
such an admittedly simplified account, a typology of reading-disability subtypes might be
derived, with two questionably discrete categories and a residual category, thus illustrating a