Is dyslexia a 'big, expensive myth' (Mills 2007)? Despite the popular acceptance of dyslexia as a type of learning disability, particularly as a persistent and significant form of reading difficulty, the debate surrounding its existence, definition, and diagnosis persists (Doyle 2003). For many years now, school systems around the world have developed and implemented strategies in order to address dyslexia because it affects a considerable percentage in the population. In the United Kingdom, one out of 10 people are considered dyslexic, 375,000 children (Hayes 2005) and in other studies, 5% of the children's population (Ramus 2003). Dyslexia is widely thought to be a deficit that can be overcome with proper learning interventions; some very prominent personalities have been said to succeed over dyslexia: Hans Christian Andersen and Nelson Rockefeller, for instance.
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Scientific and academic discourse on dyslexia, which is derived from the Greek words dys meaning difficult and lexia meaning reading, is plagued by a definitional crisis (Snowling 2000; Ingram, Pianu and Welsh 2007). Until now, there is still no consensus on the definition of dyslexia. Moreover, issues on categorisation also face the dyslexia community (Lyon, Shaywitz, and Shaywitz 2003). This is perhaps because poor reading is influenced by a myriad of factors: socio-economic disadvantage, poor diet, poor living conditions, and others. This paper centralises on the controversy on whether or not a) it is possible to differentiate 'dyslexics' from 'garden-variety poor readers' and b) it is useful to make such a differentiation. The issue of differentiation has significant implications and until now, psychologists and academic writers are still debating over it. Treating dyslexia as a distinct entity seems logically sound. In every class, there are students who do very poorly in reading but exhibit higher ability in other competencies. There are also those who do poorly in reading and in generally all other competencies. In terms of diagnosis, some claim that differentiating dyslexics from poor readers will enable educators to development the most suitable interventions. Nonetheless, the definitional crisis over dyslexia makes it a dilemma to make that diagnosis. Labelling someone as 'dyslexic' actually makes the assumption that existing literature and empirical data have generated more precise insight into what dyslexia is. The fact of the matter is experts have only agreed to disagree on the criteria by which dyslexia is diagnosed, including the types of intervention necessary to help children overcome their reading difficulties (Rice and Brooks 2004). The peril of differentiating 'dyslexics' and 'garden-variety poor readers' without any clear and conclusive parameters for diagnosis is that in the end, students with temporary reading difficulties may be branded dyslexics needlessly and students who are in genuine danger may not be getting the appropriate learning interventions they need.
Due to the unstable and inconsistent definitions of dyslexia, some academic writers have questioned whether the disorder really exists. Some people view dyslexia as a 'social and emotional construct' (Elliott 2005, p. 485) and politicians claim the impairment as a 'fictional malady' (Hayes 2005, p. 1) to suggest that dyslexia is an artificial disorder concocted by the school system to promote their interests or to hide weaknesses in language instruction. Some have even claimed that dyslexia has a class bias: that it is the middle-class way of covering up intellectual weakness. Despite these allegations, the dyslexia movement worldwide has gained wide acceptance and scientific endeavours, which although inconclusive have provided greater insight into how this impairment can be overcome by children and adults.
This paper explored recent literature on dyslexia, its definitions, causes, and critically discussed the issue of differentiation between dyslexics and garden-variety poor readers, how such a difference could be diagnosed, and its implications. The paper concludes that while there are proposed methods of evaluation, there remains no conclusive means of differentiating 'dyslexics' and 'garden-variety poor readers.'
1 Dyslexia: definitions and causes
1.1 The reading process
In order to critically examine dyslexia, models of the reading process need to be reviewed. There have been two predominant theoretical models to answer the questions: 'how do children read?' and 'how do they learn how to read?' (Harrison 2000, p. 35).
Kenneth Goodman (1970, as cited in Harrison 2000) explained that reading was a selective process which requires children to use minimal language cues but maximum contextual information. In what he calls the 'psycholinguistic guessing game,' Goodman argued that the objective of reading is not word or letter recognition but to make sense of it - the construction of meaning.
Recent studies have shown the fluent reading requires a fairly complete and rapid visual processing of text while hypothesising or guessing as Goodman (1970) suggested has a small role to play in word recognition. The most widely accepted model of reading among experts and psychologists is the 'interactive model' which states that the reading process is largely supportive of the bottom-up model as well as the input of top-down processes when required (Harrison 2000). This means that in order for individuals to read fluently, what occurs is automatic, rapid, and context-free word recognition having a fixation duration dependent on the relative word frequency of separate words.
Stanovich (1980) attempted to incorporate what is known about skilled and unskilled reading into the interactive-compensatory model. A key concept of this model of reading is that 'a process at any level can compensate for deficiencies at any other level' (p. 36). Stanovich's model was a response to both bottom-up models and top-down models which had their own problems. One of the problems for the top-down model is that for many texts, the reader has littlele knowledge of the topic and cannot generate predictions. While the top-down models may explain beginning reading, with slow rates of word recognition, they do not accurately describe skilled reading behavior. Stanovich (1980) argued that good readers recognised words rapidly because their recognition was automatic. It was poor readers, by contrast, who needed to make the greatest use of context in order to facilitate word recognition, and they did so at the expense of needing to devote extra time to this part of the processes. The obvious implication of this model is that accurate, rapid word recognition is really important in fluent reading.
1.2 Defining Dyslexia
Dyslexia is difficult to define. Although there have been several definitions introduced since its inception, experts have relied on identifying exclusionary and inclusionary characteristics to define who has dyslexia (Rice and Brooks 2004). Fletcher and Lyon (2008) offered three primary reasons why dyslexia is hard to define. First, dyslexia is 'unobservable construct' meaning that attempts to measure it are imperfect and people suffering from the disorder cannot objectively report it. Second, dyslexia is 'dimensional,' meaning that there are varying degrees to which individuals may experience difficulty, from minor, severe, and even in-between. Third, what characteristics to include and what to exclude have been a site for great disagreement among practitioners and psychologists. Nevertheless, common points in several definitions can be seen are elaborated in this paper.
A specific learning disability
Defining dyslexia as one disorder among a whole umbrella of learning disabilities (LD) has been criticised (Shaywitz, Morris and Shaywitz 2003; Snowling 2000). Studies have shown that among all learning disabilities, reading disability is the most prevalent, affecting 80% of people diagnosed with learning disabilities. In the past, LD encompassed a broad selection of difficulties experienced by children and adults in several competencies: reading, listening, writing, mathematics, and speaking. Dyslexia is now defined as a 'specific learning disability' (Shaywitz, Morris, and Shaywitz 2003, p. 2).
Some definitions on dyslexia describe the different areas impaired. The British Association of Dyslexia (2010) defines dyslexia as 'a specific learning difficulty which mainly affects the development of literacy and language related skills' wherein difficulties may experienced in rapid naming, working memory, phonological processing, processing speed, and other skills. The definition also elaborates that dyslexia may occur among people who are of normal or average intelligence. Shaywitz, Morris, and Shaywitz (2003) explained that among the indicators of dyslexia may be poor spelling, inaccurate word recognition, and poor decoding abilities. The National Centre for Learning Disabilities treats dyslexia as a 'language processing disorder' which may impair reading, writing, spelling, and speaking.
Dyslexia Scotland (2010) defined dyslexia as a specific leaning difficulty affecting almost 10% of the population. Dyslexics are said to experience difficulty in reading, spelling, writing, and mathematics. It explained that dyslexia occurs as a consequence of poor short-term memory; hence, dyslexics do poorly in learning abilities because they are unable to maintain the sequencing of numbers, words, or simple instructions.
The Miles Dyslexia Centre (2010) defined dyslexia 'as a combination of abilities and difficulties which affect the learning process in one or more of reading, spelling, writing and sometimes numeracy/language' (n.p.). Dyslexics have weaknesses in the following areas: memory, processing speed, short-term memory, visual perception, auditory perception, spoken language, and motor skills. Nevertheless, their definition of dyslexia also reiterates that in place of such weaknesses, dyslexics are gifted with creative or oral skills and that the impairment occurs regardless of socioeconomic or linguistic background.
In addition, the National Strategy for Improving Adult Literacy and Numeracy Skills point out that dyslexia is the result of poor phonological processing and poor short-term memory. Hence, dyslexics often struggle with following instructions, copying notes from the board, and difficulty in reading (Department for Education and Skills 2004).
The Dyslexia Institute (2002) also outlined some of the shortcomings of dyslexic individuals, such as: 1) difficulty in processing real-time information due to poor short-term memory or working memory, 2) problems in the phonological process which make them struggle in associating letters to sounds, and 3) problems in visual processing.
A neurobiological dysfunction
Many definitions focus on the neurobiological origins of dyslexia (Shaywitz, Morris, and Shaywitz 2003; Nicolson and Fawcett 2005). Dyslexia is seen not as a consequence of impaired vision or poor intelligence, but as a neurological disorder which has caused brains of individuals to interpret and process information in a different manner (National Centre for Learning Disabilities 2007). The National Institute of Health (2008) also viewed dyslexia as 'a problem with the brain's ability to recognise and process symbols' which may affect children's capacity to separate sounds in spoken words or in rhyming - skills which are fundamental in the reading process.
The National Institute of Neurological Disorders and Stroke (NINDS 2010) indicates that dyslexics experience difficulties with writing, phonological processing and rapid visual-verbal responding. It defined dyslexia as 'a brain-based type of learning disability that specifically impairs a person's ability to read. These individuals typically read at levels significantly lower than expected of them despite having normal intelligence' (NINDS 2010, n.p.). While the effects of dyslexia vary, the most common characteristics among dyslexics are said to include phonological processing, spelling, and rapid verbal-visual response. Dyslexia is also heritable and recent studies have pointed to genes which make individuals predisposed to the learning disorder.
A phonological deficit
Secondary to the biological basis of dyslexia is that it is the consequence of a phonological deficit.
The phonological deficit hypothesis originated from Pringle Morgan, considered to be the father of dyslexia (Snowling 2001). According to this hypothesis, reading entails the segmentation of texts into the smallest units of language called graphemes. Graphemes are then converted to phonemes which then become then complete sound of a word. For this to take place, the reader needs to assemble and address the phonology of a word. Dyslexics have difficulty in phonemic representations and phonemic recall due to poor short-term memory and other weaknesses in brain mapping.
The International Dyslexia Association (IDA 2008) describes dyslexia a language-based type of learning disorder. Dyslexics experience difficulty in developing fluent single-word decoding skills. Furthermore, Fletcher et al. (2002, as cited in Rice and Brooks 2004) supported the notion that dyslexia indicates a problem with phonological processing. Accordingly, children who suffer from dyslexia are identified when they appear a deficit in the skills of words recognition which is associated with rapid naming and phonological memory.
In addition, Snowling (2001) considered the importance of phonological processing as one of the etiology of dyslexia. Therefore, this definition focuses on the issues with word-decoding more than reading comprehension, which are controversial and critical point to distinguish between children who have specific difficulties in reading and those who have more problems and weaknesses in language. Finally, this definition is clear by clarifying that dyslexia includes some difficulties in spelling and other writing skills. Snowling (2001) attributes dyslexia to weaknesses in language that affect the development of reading and spelling with dyslexic people. The phenomenon of weakness in language do not affect the reading directly, but also affect the development of the spoken language, which is the basic foundation for learning to read. Snowling (2009) then defined dyslexia as:
A specific form of language impairment that affects the way in which the brain encodes the phonological features of spoken words. The core deficit is in phonological processing and stems from poorly specified phonological representations. Dyslexia specifically affects the development of reading and spelling skills but its effects can be modified through development leading to a variety of behavioural manifestations (pp. 213-214).
This definition stresses the importance of focusing on the ability to read text not only accurately, but also rapidly and with the importance of proper expression. The acute shortage in the development of fluent reading is characteristic of dyslexia, which continues into adulthood, even if accuracy evolved. Therefore, the importance of reading fluently must be encouraged dyslexic children who read accurately but not fluently will pass unnoticed.
Fletcher et.al. (2002, as cited in Rice and Brooks 2004) agreed that most students with dyslexia frequently encounter problems in reading comprehension because of the difficulties in the accuracy and fluency of word recognition. They may also suffer from these problems even if the skills of the accuracy and fluency were improved because of weaknesses in vocabulary as well as in language abilities.
One of the most popular and widely-used definition dates back to 1928 and developed by The World Federation of Neurology: 'A disorder manifested by difficulty learning to read, despite conventional instruction, adequate intelligence and sociocultural opportunity. It is dependent upon fundamental cognitive disabilities which are frequently constitutional in origin' (as cited in Gustafson and Samuelsson 1999, p. 127).
This definition is the basis of what is known as the discrepancy-based view of dyslexia (Fletcher et al. 2007). This definition assumes dyslexia as an 'unexpected' difficulty in reading. By 'unexpected,' dyslexia is taken to occur as a reading disorder in a child or an adult who despite having all the various factors crucial to developing fluent reading (motivation, intelligence, good instruction) still struggles with reading (Shaywitz 1998). More challenging has been the question of how to operationalise the unexpected nature of dyslexia. This has been achieved by allowing a certain amount of discrepancy between a child's level of intelligence (evaluated through an IQ test) and reading ability. Some schools use the absolute discrepancy involving 1 to 1.5 standard deviations across scores while others use the regression-based model of ascertaining the correlation between reading achievement and IQ.
The discrepancy-based definition of dyslexia provides the basis for the categorisation of 'dyslexics' with 'garden-variety poor readers'. Genuine dyslexics are those who despite having average intelligence struggle with reading while 'poor readers' are those who struggle with reading because of intellectual weakness and other demographic and sociocultural factors.
The phonological deficit is considered as the cognitive basis to dyslexia (Snowling 2001; Vellutino et al. 2004). Nonetheless, this deficit is also viewed as secondary only to other deficits such auditory temporal processing deficits (Tallal 1980) or low-level visual deficit induced by inhibitions in the magnocellular system (Livingstone, Rosen, Drislane, and Galaburda 1991).
1.3 Visual Processing in Dyslexia
The most dominant etiological explanation for dyslexia had been that it was phonological deficit and not the result of problems in visual functioning or processing. However, in the 1980s, several researchers undertook systematic studies and found that many dyslexic readers experienced visual deficits. For instance, Getman (1985, as cited in Ramus 2003) attributed problems in visual tracking to oculomotor deficiencies as well as a supposed deficit in the transient visual system. This theory has been discredited by several controlled experiments but the hypothesised effect of the transient visual system gained empirical interest.
While proponents of theories attributing dyslexia to visual deficits do not exclude other explanations, the relationship between dyslexia and problems in visual processing has spurred academic interest in the subject. The main theory behind such systematic reports indicates that dyslexia is caused by a deficit in the transient system or the magnocellular system in the visual pathway.
The magnocellular-deficit theory explains that two parallel systems lead the visual pathway from the eyes to the visual cortex: the magno- (large) and parvo- (small) cellular systems. The larger system consisting of large cells possesses high conduction velocity as well as sensitivity to rapid movement and stimulus changes. The smaller system is sensitive to fine spatial details and color. Dyslexia occurs among people which have magnocellular systems that have reduced sensitivity (Lovegrove, Garzia, and Nicholson 1990). The magnocellular system indirectly influences the parvocellular system by pressuring the latter in the course of the reading process. As one reads, there occurs a series of fixations followed by saccades or short rapid eye movements. The magnocellular deficit theory proposes that the larger system is stimulated by the saccades and the parvocellular system by the fixations. Dyslexia occurs when there is inhibition in the magnocellular system, consequently suppressing activity in the parvocellular system.
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While a number of psychologists and writers have accepted the magnocellular deficit theory, there have also been counterproductive results. For instance, in a review of contrast sensitivity studies which support the magnocellular deficit theory, Skottun (2000) found the studies which are consistent with the theory are outnumbered by studies that disprove it. An explanation behind the conflicting results is the lack of definite parameters to diagnose dyslexia. One author has alleged that the confirmability of the magnocellular deficit theory is confined to only one subtype of dyslexics (Borsting et al. 1996, as cited in Skottun 2000).
1.4 Auditory Processing in Dyslexia
Another alternative explanation to dyslexia does not discount the deficit as phonological in nature but sees it more as one that stems from an auditory deficit in 'temporal processing.' This theory is based on Tallal (1980) who proposed that children who are poor readers have difficulty processing brief or rapidly changing acoustic events whether used in speech or not. Hence, children find it difficult to judge the temporal order of nonspeech tones presented but stop-consonant-vowel syllables as well. This deficit interferes with their overall speech perception which is crucial to normal development of language, in turn, a fundamental requirement in reading.
Tallal and colleagues arrived at this hypothesis after studying children with language impairments. When presented with high and low tones at long (400ms) and short (50 ms) interstimulus intervals (ISIs), the children were found unable to make temporal order judgments (TOJ). Tallal (1980) found that compared to normal readers, dyslexics performed poorly when presented long ISIs. From this observation, Tallal made an inference that dyslexics have a 'non-linguistic deficit in temporal resolution of rapidly changing auditory stimuli' which impairs speech perception. Tallal also inferred that this deficit underlies the phonological problem.
Studies which replicated Tallal's work had mixed findings. Reed (1989, as cited in Ramus 2003) found that when using stop consonants and tones, dyslexics performed poorly compared to normals in making TOJs but performed equally with normals when presented with steady state vowels. Other studies lent support and contradiction to Tallal's hypothesis. For instance, Mody, Studdert-Kennedy, and Brady (1997) concluded that dyslexics suffered from speech discrimination deficits rather than TOJs.
In sum, evidence suggesting a direct link of temporal processing deficit to dyslexia has not been established. The auditory disorders that are observed in individuals with dyslexia are not particularly 'rapid' or 'temporal' in nature. These disorders are restricted to a subset of the dyslexic population, and have little influence on the development of phonology and reading. It therefore seems that the phonological deficit that is characteristic of dyslexia can arise in the absence of any auditory disorder, with the most severe auditory impairments nevertheless acting as aggravating factors (Ramus 2003).
2. Does dyslexia exist?
There is also some debate on whether it is meaningful to speak of dyslexia as a distinct disorder in relation to other individuals classified as poor readers. If it can be proven that there is no significant difference among individuals diagnosed with dyslexia and your average or garden-variety poor reader, then it would make sense to question whether to study dyslexia at all.
2.1 Difference between 'dyslexics' and 'garden-variety poor readers'
Gough and Tumner (1986, as cited in Siegel 1992) introduced the concept of the garden-variety poor readers in order to separate dyslexics from poor readers found to be poor in language, listening, verbal knowledge, decoding skills or pronunciation language. The authors differentiated dyslexics from the poor readers by diagnosing them as low in decoding skills but not long in listening.
Behind this differentiation is the definition of reading disability based on an aptitude-achievement discrepancy (Stanovich 1991). There were children who were observed to be poor readers but perform well in other skills. On the other hand, there were poor readers who perform poorly in intellectual skills. This discrepancy criterion made the key assumption that: poor readers with a high aptitude (based on IQ test scores) were neurologically and cognitively different from poor readers with a low IQ. Hence, clinically, the term 'dyslexic' came to mean only children with significant discrepancy in reading ability and intelligence.
The discrepancy criterion is the basis of legal statutes governing special education practice in the U.S. and elsewhere. Academically, research definitions of dyslexia use this criterion widely. Dyslexia is officially diagnosed using the discrepancy criterion in the ICD-10 Classification of Mental and Behavioural Disorders (World Health Organisation 1993), and to the Diagnostic and Statistical Manual of Mental Disorders-IV [DSM-IV]. Before a child or adult is diagnosed as 'dyslexic,' his or her reading achievement must be considerably lower than what is expected of him or her by age and IQ score. Valtin (2010) concludes that using this criterion, dyslexia is then defined as 'a medical, eetiological concept of specific reading impairment in children of normal intelligence, due to genetic or neuropsychological deficits'(p. 3) while normal reading disability occurs in children tested as having subnormal intelligence.
The operationalisation of the discrepancy concept has been critiqued as a 'reification' of something that has not been substantiated empirically (Stanovich 1994). The basic assumption is that a child or adult's intellectual capacity is the norm for determining reading underachievement. Hence, the degree of discrepancy of reading ability from IQ was judged as meaningful, 'in the almost total absence of empirical evidence' (Stanovich 1994, p. 581). Children with reading disabilities were categorised as RD-D or reading-disabled with IQ discrepancy (dyslexics) and RD-N (reading-disabled without IQ discrepancy (poor readers).
Supporters of the discrepancy criterion argue that differentiation among poor readers assists in determining which learning interventions suit groups of reading-disabled children. Because dyslexics suffer from reading disorders without showing measurable signs of intellectual weakness, their needs are different from those who read poorly because of low IQ, socioeconomic disadvantage, health problems, and others. There are many however who question its usefulness in diagnosis because dyslexics and garden-variety poor readers experience the same weaknesses in spelling and reading (Valtin 2010). Moreover, the task of differentiating children with reading disorders into dyslexics and garden-variety poor readers is a largely arbitrary one (Rice and Brooks 2004) because it may be diagnosed under one method but not in another. Because there is no clear-cut definition of dyslexia, it has been considered a 'construct' to refer to descriptive characteristics and not due to any cognitive dysfunctions (Rice and Brooks 2004).
2.2 Diagnosing differences between 'dyslexics' and 'garden-variety poor readers'
It is also relevant to review existing literature and empirical data to conclude that it is scientifically possible to distinguish which children are dyslexics and which are garden-variety poor readers. While some findings have pointed to noticeable differences between dyslexics and poor readers, they are mixed and cannot be considered unequivocal evidence to suggest differences in both groups.
Rice and Brooks (2004) listed several studies that suggested moderate differences in the performance of dyslexic and poor readers on a few reading-related tests but these differences are overrun with similarities in performance of the same groups in tests measuring reading-related characteristics such as reversal errors in alphabet, digital sequencing errors, spelling of sight vocabulary, phonemic segmentation, and pseudoword reading. Moreover, studies (Fawcett et al 2001, Jorm et al 1986, as cited in Rice and Brooks 2004) have also found that garden-variety readers had lower scores than dyslexics in the areas of rhyme task, memory span, segmentation, and pseudoword repetition.
Badian (1994) conducted an experimental study to secure support for the treatment of dyslexia as a separate entity by proving that dyslexics and garden-variety poor readers differ significantly in cognitive skills which are reading-related. Using 110 children subjects grouped into three - dyslexic, garden-variety poor readers, and good readers, Badian (1994) found that it is empirically sound to differentiate dyslexics from garden-variety poor readers. While nonword reading and phonological awareness among dyslexic and garden-variety poor readers were both low in comparison to good readers, the study found that dyslexics had unique weaknesses in phonological coding of graphic stimuli and automatic visual recognition, consistent to Stanovich's phonological-core variable-difference model of dyslexia.
Aaron (1989) also found differences between dyslexics and non-dyslexic poor readers in an experimental study on reading comprehension but not on word reading. Using two groups of primary-level poor readers, one group diagnosed as dyslexics (normal IQ scores) and the other as NSRD (nonspecific reading-disabled) or those having below normal IQ scores. The dyslexics were inferior than other two groups in terms of spelling and decoding, were more context-dependent when it came to word recognition, and did the worst on inferential comprehension.
Ellis, McDougall, and Monk (1996) had somewhat contradicting results with Aaron (1989). Using four groups - dyslexics (mean IQ 118), normal readers (mean IQ 107), and garden-variety poor readers (mean IQ 80), and precocious readers (mean IQ 126) - the study measured reading accuracy as a measure of reading ability. They concluded that dyslexics and garden-variety poor readers had insignificant differences in decoding skills, consistent with Siegel's (1992) claim and Stanovich's (1994) assertion. Moreover, unlike Aaron's (1989) earlier finding, the poor readers obtained lower scores on comprehension of text and listening comprehension compared to dyslexics.
The lack of scientific rigour in some of the psychometric tests and research on differentiation has also been criticised. Two control groups are required to undergo such experiments. Controlling for confounding variables in the tests is also difficult. Researchers need to take note of demographic and psychometric measures to establish validity of the findings (Chiappe et al. 2001, as cited in Rice and Brooks 2004). While Aaron (1989) and Badian (1994) gathering encouraging results that support differentiation, they also accepted several methodological issues with their experiments. First, the definitions were not uniformly used. There were considerable age differences in the sample of normal readers and garden-variety poor readers as well as the type of experimental design used.
2.3 Relationship of intelligence and dyslexia
The discrepancy-based criterion in diagnosing dyslexics is largely because of a few prominent and highly gifted dyslexics known in history. Hence, dyslexia has come to be known as a disorder afflicting individuals who are otherwise intelligent but have difficulty reading. However, as Siegel (1992) explains, there is absolutely no scientific data suggesting that only intelligent people have dyslexia or that people considered of low intelligence cannot suffer from dyslexia.
The reason why level of intelligence is used to isolate individuals having reading programs is that the IQ score is the best measure of someone's intellectual capacity. Hence, people with a high IQ can be said to have greater intellectual capacity than those who have lower IQ. In the context of the reading-disabled, a dyslexic is someone who cannot perform up to their maximum potential because of neurobiological or genetic factors. Intelligence scores also
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