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 [HT.1 - transfer of copyright] dated 18:00 14th January 2010

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 .....  

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.

PICmarshalletal1973.gif

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 .....

7 - References

See the Master References List

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