Correspondence
Dyslexia
N Engl J Med 1998; 338:1852-1853June 18, 1998
- Article
To the Editor:
Shaywitz (Jan. 29 issue)1 claims that the “central” problem in developmental dyslexia involves “difficulty developing an awareness that words, both written and spoken, can be broken down into smaller units of sound and that, in fact, the letters constituting the printed word represent the sounds heard in the spoken word.” If this is so, why do so many of the children with dyslexia that I examine write “cough” as “koff” and read “pint” to rhyme with “hint” and “mint”?
The normal reading system involves (at least) two parallel routes for assigning sound and meaning to sequences of letters.2 The sublexical route (“phonics”) associates each letter (or cluster of letters) with its regular sound value; the lexical route (“sight vocabulary”) associates the visual word as a whole with its meaning and pronunciation. Most children with dyslexia have problems with both processes.3 Nonetheless, there remain substantial numbers who are overly reliant on the lexical route and hence have great difficulty in “sounding out” new words (phonologic dyslexia).4 These are the children that Shaywitz must have in mind. But there are also many dyslexic children who rely primarily on sublexical processes (surface dyslexia) and hence make reading and writing errors of the type I mentioned above.
These children manifest reading difficulties (in English, but to a far lesser degree in Italian or Spanish) precisely because they have acquired the core skills that Shaywitz claims are impaired in developmental dyslexia. What they lack is an adequate sight vocabulary. The phonologic model will not help them with “shoe” or “poet.” It is important to make the correct differential diagnosis; the appropriate method of behavioral remediation depends crucially on the particular pattern of impaired and preserved functions of reading and writing in the individual child.3,5
5 ReferencesJohn C. Marshall, Ph.D.
Radcliffe Infirmary, Oxford OX2 6HE, United Kingdom1
Shaywitz SE . Dyslexia. N Engl J Med 1998;338:307-312
Full Text | Web of Science | Medline2
Marshall JC ,Newcombe F . Patterns of paralexia: a psycholinguistic approach. Psycholinguist Res 1973;2:175-199
CrossRef | Web of Science3
Castles A ,Coltheart M . Varieties of developmental dyslexia. Cognition 1993;47:149-180
CrossRef | Web of Science | Medline4
Temple CM ,Marshall JC . A case study of developmental phonological dyslexia. Br J Psychol 1983;74:517-533
CrossRef | Web of Science | Medline5
Weekes B ,Coltheart M . Surface dyslexia and surface dysgraphia: treatment studies and their theoretical implications. Cognitive Neuropsychol 1996;13:277-315
CrossRef | Web of Science
To the Editor:
Oculomotor dysfunction has frequently been thought to be a cause of dyslexia; Dr. Shaywitz emphasizes the language origin of dyslexia. Proponents of the anatomical and language origins of dyslexia tend to imply that these origins may actually preclude corrective treatment. Therefore, a visual treatment that is effective should add credibility to support for an ocular-motor cause for dyslexia.
My experience suggests that phonologic processing is, indeed, very important for the first two or three years of the period during which a child learns to read. Children with dyslexia, by definition, would find such processing burdensome, with moving, jumping, and blurry words. That is an expected deficiency in children with dyslexia in which ocular-motor dysfunction is the primary cause. Use of new reading and writing methods allows children with dyslexia to compensate and attain normal reading abilities.1
1 ReferencesGeorge T. Manilla, M.D.
Elko Clinic, Elko, NV 89801To the Editor:
As described by Dr. Shaywitz, children with dyslexia do not easily acquire the basic phonologic skills that serve as prerequisites to reading, and consequently such concepts as phoneme awareness must be taught explicitly. My colleagues and I have recently tried a novel strategy to achieve this: using the sign-language alphabet to augment verbal-language training. I believe that the use of the manual alphabet may be a simple and inexpensive method of helping children with severe dyslexia recognize phonetic elements.
Håkan Melhus, M.D., Ph.D.
Uppsala University Hospital, S-751 85 Uppsala, SwedenTo the Editor:
Regarding “unconventional approaches” to treating dyslexia, Dr. Shaywitz states that “there are very few credible data to support the claims made for these treatments.” To my knowledge, there are no prospective controlled studies that demonstrate the long-term value of any approach to the management of dyslexia. In the absence of any confirmed effective treatment, I suggest to the parents of children with dyslexia that they stick with treatments that are closest to the act of learning to read instead of stepping through obstacle courses as a means of kinesthetic training for vestibular dysfunction or trying remedies such as spinal manipulation. The lack of definitive proof of an effective treatment for dyslexia remains a problem, however, since substantial resources, both public and private, are being devoted to methods of remediation with uncertain benefit.
Lawrence H. Diller, M.D.
2099 Mt. Diablo Blvd., Walnut Creek, CA 94596Author/Editor Response
Dr. Shaywitz replies:
To the Editor: Dr. Marshall's letter introduces the concept of dual-coding models of reading. According to this theory, word identification can occur through either of two routes — one phonologically mediated, the other orthographic (direct access). In the phonologically mediated route, orthographic characters are converted to phonologic representations, and then these are matched to their lexical representations. The orthographic route is thought to involve direct coding from the orthographic characters to the lexical representations.1 Other theoretical models of reading have recently been proposed — for example, models based on parallel distributed processing architectures. Whichever theoretical model one chooses, however, increasing evidence indicates that phonologic processes are critical to the recognition of printed words and, furthermore, raises questions about whether lexical access can ever operate in a purely nonphonologic way.2 The interested reader is referred to Bernstein and Carr3 for a comprehensive review of the theoretical models of word identification.
More to the point, as noted in my article, converging evidence from a number of lines of investigation indicates that deficits in phonologic analysis consistently distinguish children with dyslexia from those who are not reading impaired. A recent study designed to examine subtypes of dyslexia in a sample of almost 400 children seven to nine years old with and without dyslexia found that all but one subtype involved difficulties in phonologic processing. The one exception was a subtype involving slow readers; no evidence of an orthographic subtype was identified.4 Furthermore, a recent study in which functional magnetic resonance imaging was used to examine the neural substrate of dyslexia found a disruption in the neural systems of readers with dyslexia when they engaged in tasks that made phonologic demands but not when they engaged in a task that made orthographic demands.5
Dr. Manilla suggests a role for the visual system in dyslexia and proposes a visual treatment. Theories relating the visual system to dyslexia were noted in my article (references 25 and 28). To date there is no evidence that interventions based solely on visual treatments are effective. Dr. Melhus reports his experience teaching children with dyslexia to read using a manual alphabet. No controlled studies are available that support this intervention.
Dr. Diller cautions against the use of unconventional approaches to treating dyslexia. Although I certainly agree with him on this, I think he is too nihilistic in questioning the value of any approach to dyslexia. In fact, recent studies supported by the National Institute of Child Health and Human Development indicate that instruction in phonologic awareness promotes the acquisition of reading skills (references 31, 36, 37, 38, and 39 of my article).
5 ReferencesSally E. Shaywitz, M.D.
Yale University School of Medicine, New Haven, CT 065101
Coltheart M. Lexical access in simple reading tasks. In: Underwood G, ed. Strategies of information processing. London: Academic Press, 1978:151-216.
2
Lukatela G ,Turvey MT . Visual lexical access is initially phonological. 1. Evidence from associative priming by words, homophones, and pseudohomophones. J Exp Psychol 1994;123:107-128
Web of Science3
Bernstein SE ,Carr TH . Dual-route theories of pronouncing printed words: what can be learned from concurrent task performance? J Exp Psychol Learn Mem Cogn 1996;22:86-116
CrossRef | Web of Science4
Morris RD, Steubing KK, Fletcher JM, et al. Subtypes of reading disability: coherent variability around a phonological core. J Edu Psychol (in press).
5
Shaywitz SE ,Shaywitz BA ,Pugh KR , et al. Functional disruption in the organization of the brain for reading in dyslexia. Proc Natl Acad SciU S A 1998;95:2636-2641
CrossRef | Web of Science | Medline
- Citing Articles (2)
Citing Articles
1
Pierluigi Zoccolotti, Naama Friedmann. (2010) From dyslexia to dyslexias, from dysgraphia to dysgraphias, from a cause to causes: A look at current research on developmental dyslexia and dysgraphia. Cortex 46:10, 1211-1215
CrossRef2
Naama Friedmann, Limor Lukov. (2008) Developmental surface dyslexias. Cortex 44:9, 1146-1160
CrossRef
