Lecturer's Précis - Marshall and Newcombe (1973)
"Patterns of Paralexia:
A Psycholinguistic Approach"
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First published online 09:08 BST 1st May 2002,
Copyright Derek J. Smith (Chartered Engineer). This version [2.0 - copyright] 09:00 BST 3rd July
2018.
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An earlier version of this material appeared in Smith (1997; Chapter 5). It is repeated here in simplified form and supported with hyperlinks. |
1 -
Introduction
A "paralexia" is a lexical selection error, that is to say, the production of one word when another is meant, during reading out loud. "Patterns of Paralexia" was a 1973 six-case clinical report on the subject of acquired dyslexia [glossary], prefaced by a brief review of previous reports on that topic dating back to Kussmaul (1877) and Dejerine (1892). The authors' first task was to try and make sense of the widely differing symptoms reported in the early literature, and they went about this by carefully distinguishing "visual" (or "peripheral"), "semantic" (or "deep"), and "grapheme-phoneme impairment" (or "surface") dyslexia subtypes, as now defined .....
Key Concept - Visual (or Peripheral) Dyslexia: A dyslexia may be classed as
"visual", if errors indicate lack of sufficiently accurate visual
discrimination, such as in confusing F with P, i
with l, or tap with tape.
Key Concept - Semantic (or Deep) Dyslexia: A dyslexia may be classed as
"semantic", if errors "bear a semantic relationship to the
stimulus item" (p177), such as in responding "egg" when
attempting to read the word "hen". This particular type of dyslexia
is, however, quite rare.
Key Concept - Grapheme-Phoneme Conversion (or Surface)
Dyslexia: A dyslexia may be classed as "grapheme-phoneme
conversion", if there is a "partial failure of grapheme-phoneme
conversion rules" (p179), such as responding "iz-land"
when shown the irregular word "island".
The authors then present their own case histories in three blocks of two .....
2 - Cases of
"Visual Dyslexia"
The authors firstly report two cases of visual dyslexia .....
Case JL: JL was a 22-year-old
soldier, who had sustained a closed head injury in a road traffic accident two
months prior to examination. He was tested on a set of 40 CVC [=
consonant-vowel-consonant] words, and his performance was summarised as follows .....
"All
the errors could plausibly be described as visual confusions. Examples of the
errors include: dug > bug; beg > leg; pod > pool;
won > von; mar > nor. A few word-reversal errors were
noted, e.g. was > saw; and some errors involved additions, e.g. lop
> slob; pew > knew. No semantic errors were observed." (p180; italics original.)
Case AT: AT was a 49-year-old
pay clerk, who had suffered a penetrating left occipital injury 26 years
previously. He, too, was tested on a set of 40 CVC words, and his performance
was summarised as follows .....
"All
errors were visually similar to the stimulus word, e.g. was > wash;
[]; net > meet; rob > robe; den > dean; rut
> root. These errors suggest that the reading process has been contaminated
by the sound of the names of the letters; that is, the vowel is given the
pronunciation appropriate to the letter name E, O, I, U." (p181; italics original.)
3 - Cases of
"Surface Dyslexia"
The authors then report two cases of surface dyslexia .....
Case JC: JC was a 45-year-old
electrician, who had suffered "a severe penetrating missile wound" in
the left temporo-parietal region 25 years previously.
He was tested on a total of 878 stimulus words, and his performance was
summarised as follows .....
"A
few of JC's errors (approximately 2%) would appear to be visual confusions,
e.g. spy > shy. No semantic errors were observed. The vast majority
of the errors could be described as partial failures of grapheme-phoneme
conversion. Thus words containing ambiguous consonants (such as s, f, c, g,
p, r) where the phonetic value of the letter
depends upon the graphemic context are especially
difficult for JC. Examples include: insect > insist []; incense
> increase [.....]. The so-called 'rule of e' which lengthens the vowel in
such words as "bite" is very rarely applied by JC. He thus produces
such errors as bike > bik;
unite > unit." (p183; italics original.)
Case ST: ST was a 50-year-old
retired factory worker with a similar history to JC. He, too, was tested on 878
stimulus words, and his performance was summarised as follows
.....
"The
vast majority of errors fell into the same categories of faulty
grapheme-phoneme translation as did JC's errors. ST's errors on ambiguous
consonants included: resent > rissend; phase
> face []; recent > rikunt [.....]. At
least 25% of ST's errors were neologisms [glossary] and were recognised
as such; no semantic errors were observed." (p184; italics
original.)
4 - Cases of
"Deep Dyslexia"
The authors then report two cases of deep dyslexia .....
Case GR: GR was a 46-year-old
ex-serviceman, who had sustained "a severe through-and-through missile
injury in the left temporo-parietal region at the age
of 18" (p185), and his performance was summarised as follows
.....
"Psychological
examination revealed moderately severe deficits in tests of rote speech,
primary memory (digit- and word-spans), and verbal learning and recall.
Comprehension and object naming were mildly impaired. Reading, writing, and
oral spelling were grossly disturbed. Only half the letters of the alphabet
could be named [.....]. He can read many concrete nouns (approximately 45-50%
of those presented), but is very severely impaired in reading any other part of
speech.. He succeeds in reading approximately 10% of
abstract nouns and between 5 and 15% of adjectives and verbs. Of 111 function
words [glossary] of
various types [], he succeeded in reading only two. [.....] GR's errors are predominantly
semantic substitutions (e.g. speak > talk) although visual errors (next
> exit) also occur frequently." (pp185-186;
italics original.)
Case KU: KU was a 49-year-old
electronics technician, who had suffered a penetrating left parieto-occipital
gunshot wound 26 years beforehand. His performance was summarised as follows .....
"The
vast majority of KU's errors had a visual component, e.g. sour >
soup; easel > easy ... no!; intense
> interrogate [.....]. However, two semantic errors were observed: diamond
> necklace; news > paper. [.....] Despite the very small incidence
of clear semantic errors, we have classified KU as a 'deep' dyslexic because,
in addition to the semantic errors, he produced a substantial number of
derivational errors [such as] luxury > luxurious; truth >
true; anger > angry [etc. .....] Very occasionally, KU will read a
word correctly without knowing its meaning." (p187;
italics original.)
5 - The Explanatory
Model
The authors then conducted what they called a "functional analysis" of the clinical data, motivated as follows .....
"[This
approach] reflects a belief that the structural organisation of language skills
in the brain is sufficiently 'tight' to place restrictions upon types of
possible break-down. That is, brain injuries will not result in 'random'
clusters of psychological disabilities. This hypothesis does not entail a
belief in strict localisation of function; we are simply postulating [.....] a
tightly knit interdependence of the specialised functional systems which subserve linguistic performance." (p188.)
The end result of this analysis was an explanatory box-and-arrow diagram, as now reproduced .....
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The Marshall
and Newcombe (1973) Model: Here is Marshall and Newcombe's
(1973) "functional analysis" of the processes involved in reading
out loud, based upon an extended series of clinical observations of acquired
dyslexics. When reading individual words, the "visual addresses" (B)
of those words have to be excited by some sort of raw image within the
"visual register" (A). In turn, these visual addresses have to be
associated with both "semantic addresses" (C) and
"phonological addresses" (D). The critical point is that all
this processing is modular. The phonological, syntactic, and semantic
aspects of words are each provided by "functionally separable
performance systems" (p193), and once the combined excitation exceeds
the necessary recognition threshold (T) word perception can be said to have
taken place. The lexical unit in question can then be associated with an
output articulatory process (E) which determines the final response, ie. saying the word. For reasons
which will become apparent when looking at later models, we have drawn this
diagram in two forms: Layout A is the originally published form, and Layout B
has been rearranged to assist its comparison with the Ellis and Young (1988) and Kay, Lesser, and Coltheart (1992) diagrams. If this diagram fails to load
automatically, it may be accessed separately at |
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Layout A redrawn from Marshall and Newcombe (1973, p189). Layout B our re-arrangement of Layout A. This version Copyright © 2002, Derek J. Smith. |
The authors concluded as follows .....
"Dyslexic
data reveal very clearly that these linguistically distinct aspects of words
are involved in functionally separable performance systems. Accordingly,
'threshold' models of normal word recognition [.....] are required, envisaging
differential access to the two forms (phonological and syntactico-semantic)
of recoding." (pp193-194; italics original.)
6 - Evaluation
Here are the key arguments put forward in this paper, in revision point format .....
- The
authors presented six clinical case summaries, two each of visual,
surface, and deep dyslexia.
- The
visual dyslexics had difficulties processing visual aspects of the
stimuli.
- The
surface dyslexics had difficulties converting graphemes into their
equivalent phonological representations.
- The
deep dyslexics had difficulties producing a correct response, but were
strangely able to access the general semantic area of the stimulus word.
- These
data were summarised in a box-and-arrow model which included two separate
routes between visual identification and an accurate response.
7 - References
See the Master References List
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