Developmental surface dyslexias - Naama Friedmann

cortex 44 (2008) 1146–1160 1157
susceptibility of potentiophones to reading errors results
from the fact that when a reader reads a potentiophone
via the sublexical route incorrectly, she cannot know that
she has made an error because the result is another existing
word (for the effect of frequency and regularity on potentiophone
errors see Lukov and Friedmann, 2006). Potentiophones
are especially helpful in the detection of surface
dyslexia, because errors cannot be detected and corrected
by the reader, and because, unlike homophones, even reading
aloud can already indicate a deficit in reading via the
lexical route. Homophones, on the other hand require additional
comprehension tasks.
The identification of subtypes of developmental surface
dyslexia is interesting and important not only for its theoretical
implications. It also has immediate implications for
diagnosis and treatment. With respect to diagnosis of developmental
surface dyslexia, the current results suggest that it is
not enough to detect that an individual reads via the sublexical
route by assessing her performance in reading aloud.
Tasks involving lexical decision and homophone/potentiophone
comprehension are required to discover the exact locus
of impairment in the reading process.
The distinction between different loci that can cause reading
via grapheme-to-phoneme conversion can also be used to
discern developmental surface dyslexia from impoverished
orthographic lexicon that results from limited exposure to
reading. In many cases children with other types of dyslexia,
such as peripheral dyslexias, avoid reading as much as they
can (see Cunningham and Stanovich, 1998; Share, 1999; Stanovich,
1986; Stanovich and West, 1989), and as a result do
not establish a rich orthographic input lexicon. This, in
turn, results in ‘‘surface-dyslexia-like’’ reading (Friedmann
and Gvion, 2002; Friedmann and Nachman-Katz, 2004; Friedmann
and Rahamim, 2007; Nachman-Katz and Friedmann,
2007; Rahamim and Friedmann, in press). The administration
of lexical decision and homophone comprehension tasks in
addition to oral reading can help in determining whether
the child has surface dyslexia or whether it is just an impoverished
orthographic input lexicon secondary to another dyslexia.
If the deficit is found to be located at the orthographic
input lexicon, other ways will be needed to make the decision,
but if the deficit is found to be located elsewhere, in
the output of the orthographic input lexicon to the phonological
output lexicon or to semantics, this will suggest that it is
indeed a genuine surface dyslexia, and not a phenomenon
secondary to reading avoidance.
With respect to treatment, different treatment plans
should be applied to the different subtypes of surface dyslexia
– treatment for individuals with a deficit at the orthographic
input lexicon should include improving the
operation of this lexicon (see Coltheart and Byng, 1989;
Weekes and Coltheart, 1996), and establishing robust lexical
entries in this lexicon by means of mnemonics and repeated
exposure for example. However, if the orthographic input
lexicon is intact and functioning, the treatment should be directed
elsewhere. For example, the work with individuals
who have access to the orthographic input lexicon but cannot
access the phonological output lexicon and semantics should
be directed at improving these connections, and for individuals
who have surface dysgraphia alongside this type of
surface dyslexia, reading for monitoring of writing can be
trained. For those individuals who read aloud incorrectly
via the sublexical route but who understand words correctly
via the route from the orthographic input lexicon to the semantic
system, the advice should be – do not read aloud.
To summarize, developmental surface dyslexia has several
faces. The current study identified three groups of individuals
who had different subtypes of developmental surface dyslexia.
All subtypes resulted from an impaired lexical route,
which forced reading via grapheme-to-phoneme conversion,
causing difficulties in reading irregular words and potentiophones,
but they differed with respect to the locus of impairment
within the lexical route, and, as a result, in the
manifestation of the deficit in lexical decision and
comprehension.
Acknowledgements
This article is dedicated to the memory of John Marshall,
who led the way in the classification of dyslexias, was the
first to describe surface dyslexia in detail, and deeply believed
that developmental dyslexias can and should be classified
similarly to acquired dyslexias. Shalom, John. We
thank Dror Dotan, Ivana Nachman-Katz, Julia Reznick,
Maya Yachini, Michal Biran, Terri Sternberg, and Uri Hadar
for their helpful comments on the paper. This research
was supported by the Israel Science Foundation (grant no.
1296/06, Friedmann).
Appendix A
Ambiguous grapheme–phoneme and
phoneme–grapheme correspondences
in Hebrew
Ambi-phoneme letters in Hebrew
Hebrew letter Phonemes Transcript
ae(ø oi)’(glottal stop)
A
vb
B
aeø’
H
vuo
O
iy(a eei)
I
kx
Q
’ aea ?
pf
P
ssh
S
Ambi-letter phonemes in Hebrew
Phoneme Letters Transcript
a
’(glottal stop)
v
x
t
k
s
H?A
H?A
OB
XQ
Tt
KQ
Ss