Estimates of Learning Disabilities - Research Proposal Example

Learning Disabilities 2008 Learning Disabilities The term ‘learning disability’ was first defined in 1967 by the National Advisory Committee on Handicapped Children (NACHC). It refers to a group of neurobiological disorders that negatively affect numerous functional and academic skills required for successful academic performance. There are many different estimates of learning disabilities incidence among US children with great variance (1% to 30%) between them (Lerner, 2000). In 1987, the Interagency Committee on Learning Disabilities reported that 5% to 10% of the overall population might be the most reasonable incidence of LD (ICLD, 197); similarly the U.S. Department of Education (1994) estimated that at least 4% of school-aged children received special education services for LD. And finally, one of the most recent estimates reported that 7.7% of children had LD (Lethbridge-Çejku, & Vickerie, 2001) The common definition provided by the National Joint Committee on Learning Disabilities (NJCLD) identifies the key aspects of LD: “a heterogeneous group of disorders manifested by significant difficulties in the acquisition and use of listening, speaking, reading, writing, reasoning or mathematical abilities. These disorders are intrinsic to the individual and presumed to be due to Central Nervous System Dysfunction. Even though a learning disability may occur concomitantly with other handicapping conditions (e.g. sensory impairment, mental retardation, social and emotional disturbance) or environmental influences (e.g. cultural differences, insufficient/inappropriate instruction, psychogenic factors) it is not the direct result of those conditions or influences” (NJCLD, 2001, p.27). The NJCLD describes four broad categories of LDs based on the separate stages of information processing that play important role in the process of learning. This four-component model was established by the late 1960s and has been widely used up to date: 1) Input: this category of LD relates to visual and auditory perception. Visual perception disability results in a variety of difficulties in recognizing the shape and position of visually perceived objects. Reversed or rotated letters, distinguishing background objects from significant forms, and poor perception of distance and depth are the most common problems. Auditory perception disability causes problems in distinguishing minor differences in sounds which leads to confusion of words, difficulties in keeping up with the flow of conversation, etc. 2) Integration: this category of LD relates to inner cognitive operations which include interpretation, categorization, and sequencing of information and/or relating it to previous learning. Difficulties with sequencing normally results in reversing the order of letters in words, inability to use various units of a memorized sequence correctly and other. Interpretation problems lead to inability to correctly infer meaning, confusion of different meanings of the same word used in different contexts, inability to generalize, etc. And finally, categorization problems result in inability to organize information in a proper way. 3) Storage: this category of LD relates to short-term and/or long-term memory, particularly the inability to store information. 4) Output: this category of LD relates to both verbal and non-verbal aspects of output. Verbal disabilities typically involve the phenomenon of so-called ‘demand language’. Demand language is observed in situations when the circumstances for conversation are created not by the person, but by someone else: in this case a person with verbal disabilities experiences difficulties in finding answers, understanding questions, and finding the right words. Non-verbal disabilities involve problems with motor reactions: difficulties with writing are normally observed in this case (NJCLD, 2004). Deficits within any of these broad categories manifest in a number of specific LD. Reading disability is considered to be the most widespread amongst all learning disabilities: approximately 70%-80% of all LD population (Lerner, 2000). The term ‘dyslexia’ is normally used to define reading disability. Writing disability is another type of LD that involves impairment of written language such as poor handwriting, bad spelling, wrong organization of ideas, etc. The umbrella term ‘dysgraphia’ is often applied to describe this type of LD. Math disability involves serious problems with learning even the basic mathematical concepts, problems with memorizing math facts, difficulties in organizing numbers, etc (Fleischner, & Garnett, 1980). Nonverbal learning disabilities manifest in motor ineptness, bad visual-spatial skills, and poor organizational skills (Lerner, 2000). As the most widespread LD, dyslexia provides a good example of how LDs are diagnosed, treated, and what consequences they may have. Dyslexia is a specific disorder or learning disability which refers to an “...unexpected difficulty in reading in children and adults who otherwise possess the intelligence, motivation, and schooling considered necessary for accurate and fluent reading” (Shaywitz, 1998: 307). The most common types of dyslexia identified in the literature are developmental dyslexia (also termed ‘specific reading retardation’) and acquired dyslexia (also termed ‘deep dyslexia’). Acquired dyslexia is commonly associated with extensive damage of the left hemisphere or the occipital and temporal lobes, and is often termed ‘alexia’, ‘word blindness’, ‘text blindness’ or ‘visual aphasia’ (Critchley, 1970). Acquired dyslexia is characterized by the occurrence of semantic errors in reading aloud. The damage that can potentially lead to acquired dyslexia occurs in different areas of brain and its severity may differ too. Therefore, symptoms of acquired dyslexia may significantly differ in each particular case. Developmental dyslexia is defined as a ‘...specific and significant impairment in reading abilities, unexplainable by any kind of deficit in general intelligence, learning opportunity, general motivation or sensory acuity’ (Critchley, 1970; World Health Organization, 1993). This disorder is commonly associated with such conditions as problems in oral language acquisition (dysphasia), impairments of writing abilities (dysgraphia and misspelling), poor mathematical abilities (dyscalculia), insufficient motor coordination (dyspraxia), postural stability and dexterity, temporal orientation (`dyschronia), visuospatial abilities (developmental right-hemisphere syndrome), and attention abilities (hyperactivity and attention deficit disorder) (Habib, 2000). The development of reading abilities normally follows the acquisition of spoken language during the earliest stages of life. The existing evidences suggest that conversion of the written word image into its phonological equivalent in the brain is a critical component of the fluent reading ability. Consequently, failure to develop such association between letter and sound is commonly and reasonably believed to be the major characteristic of developmental dyslexia (Bradley and Bryant, 1983). However, this view is only one alternative in explaining the origins of dyslexia: similarly to autism and other childhood disorders, etiology of dyslexia is also not fully clear. Some family studies suggest that dyslexia may have strong biological (genetic) underpinning because it often runs in families (Elbert et. al., 2000). There are at least four major theories of developmental dyslexia: the phonological theory, the temporal auditory processing theory, the magnocellular theory, and the automaticity theory. Each of these perspectives relies on a solid body of empirical data, while some of them are mutually complementary. However, it is practically impossible that all the four approaches might be equally and simultaneously time in one and the same case: the growing body of empirical data suggests that many types of deficits associated with dyslexia are not present in the whole population of dyslexics. Therefore, developmental dyslexia is likely to be adequately explained only from a highly flexible perspective involving multiple theories (Ramus et. al., 2003). The most commonly used treatment strategy for dyslexia relies on educational tutoring. This treatment approach is based on the assumption that dyslexia is a non-curable disorder caused by specific information processing and the only acceptable alternative for dyslexics is to learn coping strategies specially designed for each of the numerous problems associated with the disorder (reading, spelling, memory and comprehension speed, etc). Though dyslexia is recognized as a non-preventable and non-curable disorder, further research into this disorder is likely to have essential implications for treatment. However, attempts to reveal the causes of dyslexia (e.g. specific genes) seem less important than full understanding and accurate localization of the brain areas that function abnormally in dyslexic children. Areas of the brain involved in language and reading activities function abnormally in dyslexic children – this notion underlies the existing intervention strategies in the U.K. However, the most recent research involving Chinese children demonstrates that the root cause of dyslexia may be culturally determined. Dyslexic children in China are likely to have problems with other areas of brain than English-speaking children because Chinese language is symbol-based while English language is letter-based (Slok, Perfetti, Jin & Tan, 2004). This finding has one highly important implication for treatment: a strategy proved highly effective in one cultural environment will not necessarily prove similarly effective in a different cultural setting because different areas of the brain should be stimulated to successfully treat dyslexic children in different environments. Besides, cultural determination of the root cause for dyslexia challenges the established notion of the exclusively biological basis for this disorder. Further research into the nature of other learning disorder is likely to help better distinguish between the cognitive mechanisms and brain areas involved in each specific LD and other confusingly similar disorders (e.g. auditory processing disorder, verbal dyspraxia, dyscalculia, cluttering, etc). This will exclude the possibility of the right treatment delivered to wrong patients and will probably lead to development of new effective approaches that would selectively target the specific cognitive, auditory, neurological, or visual problems underlying the disorder. References Bradley, L. & Bryant, P. E. (1983). Categorizing sounds and learning to read: A causal connection. Nature, 301, 419-421. Critchley, M. (1970). The dyslexic child. 2nd ed. London: Heinemann Medical. Elbert JC, et al. (2000). Genetic influences on behavior and development. In CE Walker, MC Roberts, eds., Handbook of Clinical Child Psychology, 3rd ed., New York: John Wiley and Son, pp. 207–244. Fleischner, J., & Garnett, K. (1980). Arithmetic learning disabilities: A literature review (Research Review Series Volume 4). New York: Teachers College, Columbia University Research Institute for the Study of Learning Disabilities Habib, M. (2000). The neurological basis of developmental dyslexia. An overview and working hypothesis. Brain, 123, 2373-2399 Interagency Committee on Learning Disabilities. (1987). Learning disabilities: A report to the US Congress. Bethesda, MD: National Institutes of Health. Lerner, Janet W. (2000). Learning disabilities: theories, diagnosis, and teaching strategies. Boston: Houghton Mifflin. Lethbridge-Çejku M, Vickerie J. (2001). Summary health statistics for U.S. adults: National Health Interview Survey, 1999. National Center for Health Statistics. Vital Health Stat 10(225) National Joint Committee on Learning Disabilities (2001). “Learning disabilities: Issues on definition-revised”, in Collective perspectives on issues affecting learning disabilities, Austin, TX: Pro-Ed, pp. 27-32. National Joint Committee on Learning Disabilities (2004). Reading and Learning Disabilities, 4th Edition. Briefing Paper [available online at http://old.nichcy.org/pubs/factshe/fs17txt.htm] Ramus, F., Rosen, S., Dakin, S. C., Day, B. L., Castellote, J. M., White, S., & Frith, U. (2003). Theories of developmental dyslexia: Insights from a multiple case study of dyslexic adults. Brain, 126, pp. 841-865. Shaywitz, S. E. (1998). Dyslexia. New England Journal of Medicine, 338, pp. 307–12. Slok W. T, Perfetti C. A., Jin Z. & Tan L. H. (2004). Biological abnormality of impaired reading is constrained by culture. Nature, 431, pp.71 - 76. Read More