How Different Definitions and Contrasting Theories Trying to Explain the Causes of Dyslexia - Essay Example

Explain how different definitions and contrasting theories trying to explain the causes of dyslexia Dyslexia, according to Utah Frith, is a concept that lacks any one single and agreeable definition. In this respect, “if we seek to explain to an outsider what dyslexia is, our answer will take different forms” (Frith, 1997: 7). Therefore, the appropriate definition of dyslexia is purely dependent on why we think a person wants to know what dyslexia is. This is because; the need to know what dyslexia is, is motivated by different concerns. One of the definitions of dyslexia that has been put across defines dyslexia as “a discrepancy between reading ability and intelligence in children receiving adequate reading instructions” (Lawrence, 2009:12). However, the above definition simply describes dyslexia as a purely behavioural disorder, which then leaves the question as to the causes of the reading failure, if there were no associated cognitive or biological aspects. Nevertheless, in an attempt to arrive at a closer definition of dyslexia, and in trying to ensure the definition incorporates all the major aspects of the disorder, dyslexia can be defined as a neural-developmental disorder that has a biological origin and behavioural signs that do extend far beyond the normal problems with written language (Frith, 1999:192). The above two definitions contrast in the sense that one implies dyslexia as a behavioural disorder, while the second definition introduces both the biological and the cognitive aspects into the definition. However, even with the definition of dyslexia carrying the cognitive and the biological dimensions, it has still been found to be unsatisfactory, with new researches and studies evolving with different definitions of the term. Despite all the complexity associated with dyslexia and its real definition, one framework, the “causal modelling framework” that was developed by Utah Frith, tries to offer an elaborate structure through which the disorder can be fully understood (Frith,1997:9). Frith’s causal modelling framework Frith’s framework for explaining dyslexia has been summarized to simply state that dyslexia is a developmental disorder, which has a biological origin that causes cognitive deficiencies in reading and writing, which are then manifested in a certain pattern of behavioural signs (Frith,1997:7). According to this framework, dyslexia as a learning disorder can be explained in three dimensions, namely the biological, cognitive and behavioural dimensions. The behavioural aspect of dyslexia is associated with the observation difficulties. Thus, problems such as difficulties to read and write, as well as poor performance in spelling and reading tests are some of the observational aspects of dyslexia, which are categorized as behavioural (Frith,1997:7). However, these behavioural problems that are identifiable in dyslexia must have certain underlying causes. This is because; the behavioural problems with reading and writing are consistent, meaning that they must be caused by other underlying factors. It is the underlying factors that cause the problems in reading and writing for persons suffering from the disorder that constitutes the cognitive dimension, which then means that a problem has been inferred in the normal working component of the brain, for example emotional factors (Griffiths&Frith, 2002:14). This then leads to the biological dimension of the disorder. This dimension combines the observable behavioural problem in reading and writing with the inferred problem of the normal working component of the brain, to derive facts such as genetic or environmental factors associated with the brain that can contribute to these difficulties (Reid, 2009:27). Frith argues that dyslexia is a condition with a genetic stipulation owing, to the fact that brain abnormality always affects areas that subserve phonological processing, thus leading to difficulties in learning to read (Frith,1997:8). Nevertheless, the role of the environment should not be undermined, owing to the fact that the environment interacts with the biological factors to impair the direct causal relationship that could exist between the biological and the behavioural aspects of dyslexia. Thus, it is the environmental factors that could be internal to the brain or external to it, which cause an intermediate level referred to as the cognitive dimension that mediates between the biological level (brain deformity) and the behavioural level (reading and writing problems). Consequently, based on the environmental factors that learners are exposed to, the dyslexia problem can manifest differently in different individuals (Stein & Glickstein, 1992:972). It is this argument of the Frith framework that leads to the evaluation of two different causal theories, and assess their explanation of the factors causing dyslexia. The phonological-deficit theory According to the phonological-deficit theory, the occurrence of dyslexia is as a result of the direct impairment in the ability to process, represent, store and retrieve speech sounds (Paulesu, et al., 1996:143). According to this theory, the learning of speech requires that there is a direct correspondence between letters and their respective sounds. Therefore, when sounds are poorly represented, stored or retrieved, then there will result a corresponding problem with the foundation for reading the alphabet systems (Snowling, 2000:41). In this respect, the phonological-deficit theory postulates that there exists a direct and straightforward linkage between the cognitive deficits of the dyslexia learning disorder and the behavioural problems that are manifested in the learners (Galaburda, Menard & Rosen, 1994:13). The explanation of the biological aspect of the dyslexia disorder under this theory is that; there is an underlying congenital dysfunction in the left-hemisphere of the brain that entails phonological representations, which then affects their representation, storage and/or retrieval (Snowling, 2000:47). In this respect, the phonological-deficit theory holds that the cognitive deficit that is associated with dyslexia is specific to phonology, and to no other aspect of the reading or learning problems. The existence of the phonological deficit is an area that has not been disputed even by the critics of this theory. The major strength associated with phonological-deficit theory is the fact that; persons suffering from dyslexia perform particularly very poorly in the areas requiring phonological awareness (Snowling, 2000:21). Learners suffering from dyslexia experience a major problem in the manipulation of the speech sounds as well as in their conscious segmentations. Additionally, the other major strength associated with the anatomical and the brain imaging studies that have been undertaken in this area, is that they have provided evidence that is supportive of the left brain hemisphere dysfunction, as being the basis of the phonological deficits (Paulesu, et al., 1996:144). However, the major weakness that is associated with the phonological-deficit theory is that persons suffering from dyslexia have exhibited slow automatic naming evidence, while also manifesting poor verbal short-term memory (Snowling, 2000:27). The short-term verbal memory is the one responsible for enabling the pronunciation of the sounds of the words, since it allows for the blending of the sounds and the words together, when a person is reading the words for the first time (Paulesu, et al., 1996:144).These cognitive problems are indicative of the existence of more basic and fundamental phonological deficits, which are not merely a matter of deficiency in representation, storage and retrieval, but more of a problem with the quality of the representation, storage and/or retrieval (Galaburda, Menard & Rosen, 1994:10). This is because; the short-term verbal memory also causes the long-term verbal memory in individuals suffering from dyslexia, such that such persons will have a problem of remembering the names of persons they have met and interacted with before. The other major weakness that is associated with the phonological-deficit theory is that it relates dyslexia to phonological deficit only, while the other characteristics exhibited by persons suffering from dyslexia have indicated a range of other motor and sensory learning difficulties, which are not specifically phonological (Snowling, 2000:33). In this respect, the phonological-deficit theory is weak in that it has only managed to discuss one aspect of a more extended disorder. Cerebellar impairment theory The cerebellar impairment theory holds that dyslexia is caused by an impairment that occurs in the cerebellum part of the brain, and since the cerebellum is required for timing the motor controls, its impairment leads to the inability to create a consistent timed-eye movement that is necessary for reading (Brown et al., 2001:782). Additionally, the Cerebellar impairment theory holds that cerebellar is responsible for the fluid interpretation of speech into sounds (Nicolson & Fawcett, 1995:43). Thus the impairment of the cerebellum also causes the phonological processing deficits, which in turn cause the problem of coordination between the words and the speech sounds. The Cerebellar impairment theory is founded on the premise that the cerebellar is the part of a brain that helps in the process of acquiring new skills, and then converting the acquired skills into an automated system (Rae, et al, 1998:49). The best example of the role of the cerebellar is its usefulness in helping the articulation of speech, through the automation of the motor and cognitive skills. The other role of the cerebellar is in the creation of both the motor and perceptual timing, such that it provides for the consistency of following the perception of the words with the pronunciation of the sounds of the words (Nicolson & Fawcett, 1995:44). Therefore, the Cerebellar impairment theory argues that individuals suffering from dyslexia have a mildly dysfunctional cerebellum, which is therefore responsible for the cognitive reading and writing difficulties that ensue for the dyslexics (Brown et al., 2001:782). The phonological difficulties experienced by the persons suffering from this disorder are caused by dysfunctional speech articulations on the part of the cerebellar, which would in turn cause the poor phonological representations. The major strength associated with the Cerebellar impairment theory is that research evidence has shown that people suffering from dyslexia do not only suffer from the reading and writing difficulties, but that they also suffer from a range of other impaired motor tasks, such as typing and driving (Rochelle & Talcott, 2006:1159). The other major strength that is in support of the Cerebellar impairment theory is that persons suffering from dyslexia have been discovered to demonstrate a high level of impaired automization of balance, when performing dual tasks (Brown et al., 2001:783). Another strength associated with the Cerebellar impairment theory is the fact that persons suffering from dyslexia have also been discovered to suffer from the problem of time-estimation, which is a non-motor cerebellar task (Rochelle & Talcott, 2006:1163). Finally, the Cerebellar impairment theory has been supported by the major strength that; brain imaging studies have shown evidence to the effect that people suffering from dyslexia have metabolic and anatomical activation differences, which are associated with the dysfunctional cerebellar part of the brain (Rae, et al.,1998:51). Nevertheless, the major weakness associated with the Cerebellar impairment theory is that the theory has not been able to show how the loss of co-ordination among the motor pathways in the cerebellar part of the brain occurs, such that there are some dysfunctional aspects of the cerebellar, while the rest of it is performing normally (Nicolson & Fawcett, 1995:46). Additionally, another weakness associated with this theory is that it has not been able to define exactly which part of the cerebellar is affected by the impairment, such that it has only asserted that there must be a certain dysfunctional part of the cerebellar (Brown et al., 2001:784). The implications for a ‘diagnosis’ The implication for diagnosis of dyslexia is that there needs to be closer attention to the motor and sensory responses of the potential dyslexics, beyond the learning problems associated with difficulties in reading and writing (Deponio, et al., 2000:33). This is because; the underlying problems of dyslexia are more brain-related according to both the Cerebellar impairment theory and the phonological-deficit theory, such that the disorder will manifest in different other ways. For example, the implication of the phonological-deficit theory for diagnosis is that; paying closer attention to the reading and speech sound pronunciation, as well as paying closer attention to the speech articulation of a person, are necessary to determine the likelihood of the person suffering from dyslexia (Snowling, 2000:32). On the other hand, the implications of Cerebellar impairment theory on the diagnosis of dyslexia is that; in addition to paying attention to the phonological characteristics manifested by a learner, there is a need to go further and assess the dual-task performance traits of the learner. This is owing to the fact that the manifestation of the lack of balance in the automization of the dual tasks may pint to the likelihood of suffering from dyslexia (Rochelle & Talcott, 2006:1161). Additionally, the Cerebellar impairment theory has the diagnosis implication of requiring the continuous assessment of the performance of the over-learned tasks such as typing and time-estimation, which are non-motorized tasks that can enable the detection of the likelihood of a person suffering from dyslexia (Rae, et al.,1998:55). References Brown W.E., et al. (2001). Preliminary evidence of widespread morphological variations of the brain in dyslexia. Neurology 56, 781–3. Deponio, P. et al. (2000) An audit of the processes involved in identifying and assessing bilingual learners suspected of being dyslexic: a Scottish study. Dyslexia: An International Journal of Research and Practice 6(1): 29–41. Galaburda A.M, Menard M.T. & Rosen G.D. (1994). Evidence for aberrant auditory anatomy in developmental dyslexia. Proc Natl Acad Sci 91, 10–13. Griffiths, S. &Frith, U. (2002) Evidence for an articulatory awareness deficit in adult dyslexics. Dyslexia 8: 14–21. Lawrence, D. (2009) Understanding Dyslexia. Maidenhead: Open University Press. Nicolson R.I. & Fawcett A.J. (1995). Time estimation deficits in developmental dyslexia: evidence of cerebellar involvement. Proc R Soc Lond B Biol Sci 259, 43–7. Paulesu, E., et al. (1996). Is developmental dyslexia a disconnection syndrome? Evidence from PET scanning. Brain 119, 143–57. Rae, C., et al. (1998). Metabolic abnormalities in developmental dyslexia detected by 1H magnetic resonance spectroscopy. Dev Neuropsychol 351, 49–52. Reid, G. (2009) Dyslexia: A Practitioner’s Handbook. 4thedn. Chichester: Wiley-Blackwell. Rochelle, K., & Talcott, J. (2006). Impaired balance in developmental dyslexia? A meta-analysis of the contending evidence. Journal of Child Psychology & Psychiatry, 47(11), 1159-66. Stein, J. & Glickstein, M. (1992) Role of the cerebellum in visual guidance of movement. Psychological Review 72(4): 968–1017. Snowling M. J. (2000). Dyslexia. 2nd ed. Oxford: Blackwell. Read More