Surface Dyslexia; by, William T GAllucci,jr.


     Within the paradigm of reading disorders, surface
dyslexia seems to affect those who have sustained brain
damage within the visual processing area. These patients
make frequent regularisation errors such as reading pint
as though it rhymed with mint when reading (Weekes`93).
Errors such as these, are characteristic of surface
dyslexia, which is impairment at the level where episodic
visual memory takes place. Single case studies, have
shown surface dyslexics to have significant impairments,
in visual processing. This affects their performance on
word-matching tasks (Goulandris & Snowling, 1991).  In
this paper, I will focus on ,Marshall and Newcomb's idea
of surface dyslexia being based on an information-flow
model of reading. Colthart's, concept of grapheme-phoneme
conversion, and Shallice and Warrington's, account of
surface dyslexia, as an interruption between the visual
word form, and semantics.
     Most studies involving surface dyslexia were
performed by Marshall and Newcomb, of which performances
of J.C. and S.T. were measured. Studies of surface
dyslexia involve reading of isolated words, and assigning
meaning to them, -- a process known, as grapheme to
phoneme conversion. They hypothesize, that somehow the
process of direct visual semantic pathways have been
impaired causing the deficit. Marshall and Newcomb,
developed their findings to formulate an idea that
surface dyslexia, assumes an information- flow model of
reading. The importance of this formulation is that it
implies that pronunciation achieved, is in no way
constrained by or dependent on lexical factors, that is ,
what the subject knows about the appearance and
pronunciation of individual words attributed to the
difficulty with the conditional and contextual aspects of
grapheme-phoneme rules. This means that, patients have
trouble reading irregular words for which there is no
direct grapheme to phoneme correspondence (alexia with
agraphia). They concluded to say; "that damage must have
affected the area where visual word images are stored".
Furthermore, they were able to define four features of
surface dyslexia; patient can read nonsense syllables,
errors are typically phonologically similar to the
stimulus, errors are very frequently phonologically
possible but non-existent lexical forms, and semantic
reading of the visual stimulus is determined by the
phonology of the response(Marshall & Newcomb 76).(
Marshall & Newcomb 76)
     Coltharts concept of surface dyslexia, focuses on
grapheme-phoneme conversion. It is a procedure that is
entirely independent of lexically held visual
specifications for words, and is even pre-lexical. He
expresses the grapheme-phoneme correspondences in terms
of phonemes, and as algorithmic contingent rules, or
productions, i.e.) vowel + consonant + final E, the vowel
is long; G or C is soft before E or I, otherwise hard.
His view of surface dyslexia, has three implications;
lack of lexical access, at least for words which are read
incorrectly, and misunderstood, and failures in parsing
the letter string into appropriate graphemes, and
misapplication, or failure to apply certain grapheme-phoneme rules.
     Shallice and Warrington's account of surface
dyslexia, is that the direct route from visual-word form,
to semantics is impaired. They argue that, damage only
permits the patients to read phonologically. Their
reasoning lies in that patients, don't conceive whole-word correspondences as a general facility, (from input
to output lexicon) nor of morphemic correspondences,
which only leaves intact their own version of
phonological recoding. Furthermore, they conclude to
state that;" the central characteristic of surface
dyslexia, is impairment to the route from visual word-form, to semantics.
     In viewing the studies of Marshall and Newcomb,
along with Colhart's. Surface dyslexia involves, patients
having the inability to recognize words directly, but can
understand them, using skills that involve sounding out
letter to sound relations. It seems as though, the words
are recognizable, if sounded out. This task or skill of
sounding out words seems to work, but only for regular
words ("home", "Dome" 0. Irregular words such as "come",
seem to be understood as, if it were "comb". Spelling
also seems to be impaired, but is phonetically correct.
The final point of interest, is that languages that are
phonetic, such as Italian, surface dyslexia is not
present in the population.




                       REFERENCES 

1) Colhart, et.al, Deep Dyslexia. Routledge & Kegan Paul,
London 1980.
2) Malatesha & Aaron, Reading Disorders. Academic Press,
New York. 1982 
3) Marshall & Newcomb, Dyslexia. Academic Press, New
York.1976
4) Weekes,B. Perceptual and Motor Skills; "A TEST OF
EPISODIC VISUAL MEMORY". 1993,VOL 77.

Copyright © 1997, Dr. John M. Morgan, All rights reserved - This page last edited March 17, 1997
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