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Abstract:
Abstract: Two related observations have prompted the view
that phonological and deep dyslexia are arranged on a continuum of
phonological processing deficits, with semantic deficits appearing
at the severe end of the continuum. The first observation is that
each disorder exhibits similar nonword reading deficits. The second
observation is that deep dyslexia occasionally resolves into
phonological dyslexia. We tested the view that these two disorders
form a continuum in two ways. First, we compared word repetition
and naming data from two deep dyslexics and eight phonological
dyslexics. While phonological neighborhood effects support the
continuum view, an examination of over-all reading performance
indicates that severity alone cannot account for the additional
semantic deficit found in deep dyslexia. Second, we conducted a
longitudinal examination of a patient who progressed from deep to
phonological dyslexia. The continuum hypothesis predicts that the
disappearance of semantic errors should coincide with improved
phonological decoding. We show that the course of improvement in
the studied patient did not support this prediction. Our patient,
SD, made a significant number of semantic errors, yet was able to
read nonwords during the first testing session. Nine months later,
SD made no errors in word reading but improved only marginally in
nonword reading. We argue that superficial support for a continuum
model of deep and phonological dyslexia is undermined by
examinations across subjects and within subjects across
time.
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