Definitions of Developmental Dyslexia - Case Study Example

Topic: Is There a Theory that Adequately Accounts for Developmental Dyslexia? Evaluate at Least Two Theoretical Attempts to do so Synopsis on Theoretical Developments 1. a. Definitions of Developmental Dyslexia: Developmental Dyslexia (DD) has been defined as “evident when accurate and fluent word reading and/or spelling develops incompletely or with great difficulty” by the British Psychological Society (BPS). It goes on to describe it as “This focuses on literacy at the word level and implies that the problem is severe and persistent despite appropriate learning opportunities. It provides the basis of a staged process of assessment through learning” (BPS, 1999). This definition is rather a functional one with focus on the subject’s reading or spelling impairment and extends to include a reference to the provision of adequate or reasonable learning opportunities to the dyslexic, so that there is not a conscious or unconscious process of exclusion. On the other hand the International Dyslexia Board (IDB) and the US National Institute of Child Health and Human Development (NICHD) adopt the following definition: “Developmental Dyslexia is a specific learning disability that is neurological in origin. It is characterized by difficulties with accurate or/and fluent word recognition and by poor spelling and decoding abilities. These difficulties typically result from a deficit in the phonological component of the language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge”. This definition is technically elaborate enough to serve as a seminal proposition to enable further analysis of the subject. Though it places emphasis on neurological aspects of the disorder, it has the necessary characteristics to capture more of the associated connotations and denotations of Developmental Dyslexia. 1. b. Theoretical Outline of Developmental Dyslexia There are so many theories on the subject of Developmental Dyslexia that have evolved ever since the disorder was first identified by Oswald Berkhan in 1881. The following are some of the commonly known theories that have attracted the attention of both professional psychologists and lay people in the recent past. I. Phonological Theory. II. Rapid Auditory Processing Theory. III. Cerebellar Theory. IV. Visual Theory V. Magnocellular Theory. I. Phonological Theory identifies Developmental Dyslexia as a peculiar impairment that affects the subject’s ability to read written language. It seeks to focus attention on the dyslexic’s impaired capacity to comprehend grapheme-phoneme correspondence. In other words it is concerned with the inability or difficulty of the dyslexic to articulate comprehensively the correspondence between the shapes of letters and their representative sounds. II. Rapid Auditory Processing Theory is based on the fast developing acceptance of a fact that the average dyslexic suffers from some auditory dysfunction as well. For example, the subject may not perform well in auditory frequency discrimination of sounds and the connected temporal order judgment in processing the sounds. III. Cerebellar Theory is based on the biological criterion. It holds that the dyslexic’s cognitive impairment is directly related to the slightly dysfunctional cerebellum. As a result the motor control of speech articulation is impaired. Secondly, cerebellum plays a pivotal role in the process of automaticity of repeatedly learned tasks. Therefore a slightly dysfunctional cerebellum again affects the dyslexic’s ability to perform well in grapheme-phoneme correspondence. IV. The Visual Theory seeks to explain Developmental Dyslexia by focusing on magnocellular and parvocellular pathways of the dyslexic. Again the theory refers to an impairment in the magnocellular pathway of the dyslexic and says that it leads to a deficit in visual capacity to process information. Abnormalities in visuospatial attention and binocular control mechanism have been noted here. V. Magnocellular Theory is regarded as the unifying theory of all foregoing theories. It modifies the Visual Theory to include that the magnocellular dysfunction is not limited to some malfunctioning in the two pathways alone but also in other spheres as well. For example, a dyslexic may exhibit a range of deficits from auditory to tactile. 2. Critical Analysis of Theories I will now critically analyse the theoretical postulates on two of the theories above and seek to cite evidence to correlate theory and empiricism. Phonological Theory has, not only, been well developed in the recent past but also well received by both the medical profession and laymen. Phonological impairment is characterized by a dualism that has rekindled the debate on the causative or trigger factors of Developmental Dyslexia (Castles and Colheart, 1993, pp.149-180). In this study the authors tested 56 dyslexic boys along with a control group of 56 non-dyslexic boys. The test was administered in two stages and the subjects were asked to read aloud a set of words and a set of non words. The majority, i.e. 55% of the first group displayed traces of phonological impairment in which they could not properly read out the sub-lexical set of words that did not have the characteristics of full words. The boys in this group were identified as having phonological dyslexia proper while the others in the same group who displayed poor lexical skills such as the inability to identify and utter irregular words were diagnosed to be suffering from surface dyslexia. The latter group had a severe impairment in identifying and pronouncing the irregular words that were picked by the non-dyslexic boys. There are other authors who tend to support phonological deficit theory though they do not seek to distinguish between surface dyslexia and phonological dyslexia. For example, a paper published in the Neuroscientist with the title “The Functional Organization of Brain for Reading and Reading Disability (Dyslexia)”, has tentatively narrowed down the scope of research on the subject to phonological deficit hypothesis so that neurological links in Developmental Dyslexia, have been brought up to tilt the discourse on the topic in favour of linguistic disability originating in the brain (Shaywitz et al, 1996, pp.245-255). The authors have rejected the coterminous principle of auditory impairment. Plausible arguments have persisted throughout the evolutionary process of the subject despite polemical inconsistencies. However, it must be noted here that the Phonological Theory is not without its fair number of critics who argue that it has invariably failed to justify its conclusions at least with regard to the theory of dual phonological dyslexia that Castles and Colheart have developed together. For instance, the authors of a paper titled “theoretical and Methodological Pitfalls in Making Comparisons” published in the journal “Reading and Writing”, argue that the research outcome of Castles and Coltheart mentioned above is questionable. “We take issue with their proposal on theoretical grounds and argue that methodological weaknesses in their study seriously weaken their claims” (Snowling, Bryant and Hulme, 1996, pp.443-451). Similarly, a number of other authors have questioned the premise that “phonological dyslexia doesn’t occur in the absence of phonological impairment”. They argue “In fact, phonological dyslexia can occur without corresponding generalized phonological impairment” (Caccappollo-van Vliet E, Miozzo and Stern, 2004, pp.820-839). Now I shall consider the Cerebellar Theory on Developmental Dyslexia. The Cerebellar Theory owes its typical epithet to the cerebellum of the brain. Cerebellum functions as a motor control mechanism in articulating speech sounds. In other words the grapheme-phoneme correspondence is basically determined by its functional capacity. Dyslexic individuals who perform well below a certain index such as Aston Index - which is used to screen and diagnose language difficulties – are supposed to have impaired motor function. In a recent research the authors measured serial reaction time performance in 40 adults (21 controls and 19 dyslexics). “The dyslexics performed comparably with controls during the randomly-ordered reaction time blocks. However, the former failed to show the reaction time reduction that the latter group showed during the repeated sequences” (Stoodley, Harrison and Stein, 2006, pp.795-798). Further, another group of researchers carried out to measure fixational stability and saccadic eye movements in 9-13 year old dyslexics with signs of subtle cerebellar dysfunction along with a group of age-matched normal readers. This group of dyslexics was chosen because cerebellar disorders are often associated with ocular motor dysfunction. Dyslexic children were found to exhibit significantly greater fixational instability than the controls while viewing a simple stationary stimulus, (Raymond, Ogden, Fagan and Kaplan, 1988, pp.174-181). Even the Cerebellar Theory of Developmental Dyslexia has some fierce critics. For instance, Larry Silver in his paper titled “Neurophysiological Approaches (A Critique)” points out that “a spate of hypotheses seeking to support that there is an indisputable correlation between cerebellar vestibular dysfunction and reading” have no empirical basis whatsoever”. He particularly faults Ayres, Frank and Levinson for their overzealous support for an otherwise inconclusive theory (Silver, 2001, Spring Issue, International Dyslexia Association). Finally, I wish to focus attention on a critique published in “Dyslexia” journal by Snowling and Hulme. The authors have damned a study carried out by Reynolds, Nicolson and Hambly(Dyslexia, 2003, 9. 48) in which the latter three claim “Dyslexia Dyspraxia Attention Deficit Disorder (DDAD) could be treated effectively by using an exercise based treatment regime for children with reading difficulties”. The authors have sought to invalidate the argument that “ DDAT is an effective treatment with positive effects on the cognitive skills underlying reading and literacy” (Snowling and Hulme, 2003, pp.127-133). In conclusion, I wish to point out that neither theory is without its own share of foibles. However, the Phonological Theory has been subject to a higher level of critical analysis thus far and it has successfully weathered such critical onslaughts and withstood the test of time. Developmental Dyslexia is a disorder that is less investigated within the classroom and society. Its current status as a multifaceted disorder actually hides more than it reveals. REFERENCES 1. Castles, A and Coltheart, M (1993), Varieties of Developmental Dyslexia, Cognition, 47(2), pp.149-180. 2. Caccappollo, E. V, Mizzo, M and Stern Y, (2004a.), Phonological Dyslexia without Phonological Impairment, Cognitive Neuropsychology, 21, pp.820-839. 3. Raymond, J.E, Ogden, N.A, Fagan, J.E, and Kaplan B. J, (1988), Fixational Instability Saccadic Eye Movements of Dyslectic Children with Subtle Cerebellar Dysfunction, Am J Optom Physiol Opt, 65(3), pp174-181). 4. Silver, L, (2001), Neurophysiological Approaches( A Critique), International Dyslexia Association, Spring Issue, (Retrieved May 24, 2008 from: dyslexia.mtsu. edu/modules/articles/display.article.jsp?id) 5. Shaywitz, B.A, Sally, S. E, Pugg, K.R, Skudlarski, P et al, The3 Functional Organization of Brian for Reading and Reading Disability(Dyslexia), The Neuroscientist, Vol. 2(4), pp.245-255. 6. Snowling, M. J, and Hulme, C (2003), A Critique on Claims from Reynolds, Nicolson and Hambly………. (2003) Dyslexia 9, pp.127-133. John Wiley & Sons Ltd. 7. Snowling, M.J, Bryant, P.E and Hulme, C, (1996), Theoretical and Methodological Pitfalls in Making Comparisons, Reading and Writing Journal, Vol. 8(5) pp.443-451. 8. Stoodley, C.J, Harrison, E and Stein J.F,(2006), Implicit Motor Learning Deficits in Dyslexic Adults Neuropsychologia, Vol. 44(5), pp.795-798. Read More

       I will now critically analyze the theoretical postulates on two of the theories above and seek to cite evidence to correlate theory and empiricism. Phonological Theory has, not only, been well developed in the recent past but also well received by both the medical profession and laymen. Phonological impairment is characterized by a dualism that has rekindled the debate on the causative or trigger factors of Developmental Dyslexia (Castles and Colheart, 1993, pp.149-180). In this study, the authors tested 56 dyslexic boys along with a control group of 56 non-dyslexic boys. The test was administered in two stages and the subjects were asked to read aloud a set of words and a set of non-words. The majority, i.e. 55% of the first group displayed traces of phonological impairment in which they could not properly read out the sub-lexical set of words that did not have the characteristics of full words. The boys in this group were identified as having phonological dyslexia proper while the others in the same group who displayed poor lexical skills such as the inability to identify and utter irregular words were diagnosed to be suffering from surface dyslexia. The latter group had a severe impairment in identifying and pronouncing the irregular words that were picked by the non-dyslexic boys.

There are other authors who tend to support phonological deficit theory though they do not seek to distinguish between surface dyslexia and phonological dyslexia. For example, a paper published in the Neuroscientist with the title “The Functional Organization of Brain for Reading and Reading Disability (Dyslexia)”, has tentatively narrowed down the scope of research on the subject to phonological deficit hypothesis so that neurological links in Developmental Dyslexia, have been brought up to tilt the discourse on the topic in favor of linguistic disability originating in the brain (Shaywitz et al, 1996, pp.245-255). The authors have rejected the coterminous principle of auditory impairment. Plausible arguments have persisted throughout the evolutionary process of the subject despite polemical inconsistencies.

 However, it must be noted here that the Phonological Theory is not without its fair number of critics who argue that it has invariably failed to justify its conclusions at least with regard to the theory of dual phonological dyslexia that Castles and Colheart have developed together. For instance, the authors of a paper titled “theoretical and Methodological Pitfalls in Making Comparisons” published in the journal “Reading and Writing”, argue that the research outcome of Castles and Coltheart mentioned above is questionable. “We take issue with their proposal on theoretical grounds and argue that methodological weaknesses in their study seriously weaken their claims” (Snowling, Bryant and Hulme, 1996, pp.443-451). Similarly, a number of other authors have questioned the premise that “phonological dyslexia doesn’t occur in the absence of phonological impairment”. They argue “In fact, phonological dyslexia can occur without corresponding generalized phonological impairment” (Caccappollo-van Vliet E, Miozzo and Stern, 2004, pp.820-839).

Now I shall consider the Cerebellar Theory on Developmental Dyslexia. The Cerebellar Theory owes its typical epithet to the cerebellum of the brain. Cerebellum functions as a motor control mechanism in articulating speech sounds. In other words, the grapheme-phoneme correspondence is basically determined by its functional capacity. Dyslexic individuals who perform well below a certain index such as Aston Index - which is used to screen and diagnose language difficulties – are supposed to have impaired motor function. In recent research, the author's measured serial reaction time performance in 40 adults (21 controls and 19 dyslexics). “The dyslexics performed comparably with controls during the randomly-ordered reaction time blocks. However, the former failed to show the reaction time reduction that the latter group showed during the repeated sequences” (Stoodley, Harrison, and Stein, 2006, pp.795-798).

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