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Dyslexia is a learning disability that makes itself manifest primarily as a difficulty with written language, particularly with reading. It is separate and distinct from reading difficulties resulting from other causes, such as a non- neurological deficiency with vision or hearing, or from poor or inadequate reading instruction. [1] suggests that dyslexia results from differences in how the brain processes written and spoken language. Although dyslexia is thought to be the result of a neurological difference, it is not an intellectual disability. Dyslexia is diagnosed in people of all levels of intelligence. [2] Dyslexia is a learning difficulty which holds no simple definition; psychologists continue to have difficulties providing clear cut answers as to what it is or how it is actually caused.
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Dyslexia - Wikipedia, the free encyclopedia
4/30/09 8:52 AM
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Dyslexia
From Wikipedia, the free encyclopedia
Part of a series on
Dyslexia is a learning disability that makes itself manifest primarily as a
Dyslexia
difficulty with written language, particularly with reading. It is separate and
distinct from reading difficulties resulting from other causes, such as a non-
neurological deficiency with vision or hearing, or from poor or inadequate
and related disorders
reading instruction.[1] suggests that dyslexia results from differences in how the
Education · Neuropsychology
brain processes written and spoken language. Although dyslexia is thought to
RELATED CONDITIONS
be the result of a neurological difference, it is not an intellectual disability.
Acquired dyslexia · Alexia
Dyslexia is diagnosed in people of all levels of intelligence.[2] Dyslexia is a
Auditory Processing Disorder
Dyscalculia · Dysgraphia
learning difficulty which holds no simple definition; psychologists continue to
Dyslexia · Dyspraxia
have difficulties providing clear cut answers as to what it is or how it is
THEORIES
actually caused.
Double deficit · Magnocellular
Perceptual noise exclusion
Phonological deficit
RELATED TOPICS
Contents
IDEA · Literacy
Reading acquisition · Spelling
Recording for the Blind & Dyslexic
1 History
2 Subtypes of developmental dyslexia
LISTS
3 Variations and related conditions
Assessments · Fields
People · Publications
4 Cross-Cultural Incidence Rate Comparison
Topics
5 Scientific research
Fiction · Treatments
5.1 Theories of developmental dyslexia
5.1.1 Evolutionary hypothesis
5.1.2 Phonological hypothesis
5.1.3 Rapid auditory processing theory
5.1.4 Visual theory
5.1.5 Cerebellar theory
5.1.6 Magnocellular theory
5.1.7 Perceptual visual-noise exclusion hypothesis
5.2 Research using functional brain scan technology
5.3 Research also indicates
5.3.1 Genetic factors
5.3.2 Physiology
5.4 Effect of language orthography
6 Characteristics
6.1 Speech, hearing and listening
6.2 Reading and spelling
6.3 Writing and motor skills
6.4 Mathematical abilities
6.5 Adaptive attributes
7 Management
8 Facts and statistics
9 Legal and educational support issues
10 Controversy
10.1 The experience of Sudbury model of democratic education
schools
11 Dyslexia in literature, film, and television
12 See also
13 References
14 External links
14.1 Associations and Charities
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14.2 Historical
14.3 Research papers, articles and media
History
Identified by Oswald Berkhan in 1881, [3] the term 'dyslexia' was later coined in 1887 by Rudolf Berlin, an
ophthalmologist practicing in Stuttgart, Germany.[4] He used the term to refer to a case of a young boy who
had a severe impairment in learning to read and write in spite of showing typical intellectual and physical
abilities in all other respects.
In 1896, W. Pringle Morgan, a British physician, from Seaford, East Sussex, England published a description
of a reading-specific learning disorder in a report to the British Medical Journal titled "Congenital Word
Blindness". This described the case of a 14-year-old boy who had not yet learned to read, yet showed normal
intelligence and was generally adept at other activities typical of children of that age.[5]
During the 1890s and early 1900s, James Hinshelwood, a British ophthalmologist, published a series of
articles in medical journals describing similar cases of congenital word blindness, which he defined as "a
congenital defect occurring in children with otherwise normal and undamaged brains characterised by a
difficulty in learning to read." In his 1917 book Congenital Word Blindness, Hinshelwood asserted that the
primary disability was in visual memory for words and letters, and described symptoms including letter
reversals, and difficulties with spelling and reading comprehension.[6]
An early researcher in dyslexia was Samuel T. Orton, a neurologist who worked primarily with stroke victims.
In 1925 Orton met a boy who could not read and who exhibited symptoms similar to stroke victims who had
lost the ability to read. Orton began studying reading difficulties and determined that there was a syndrome
unrelated to brain damage that made learning to read difficult. Orton called the condition strephosymbolia
(meaning 'twisted signs') to describe his theory that individuals with dyslexia had difficulty associating the
visual forms of words with their spoken forms.[7] Orton observed that reading deficits in dyslexia did not
seem to stem from strictly visual deficits.[8] He believed the condition was caused by the failure to establish
hemispheric dominance in the brain.[9] He also observed that the children he worked with were
disproportionately left- or mixed-handed, although this finding has been difficult to replicate.[10] Orton's
hypothesis concerning hemispheric specialization was borne out by post-mortem studies in the 1980s and
1990s establishing that the left planum temporale, a brain area associated with language processing, is
physically larger than the corresponding right area in the brains of non-dyslexic subjects, but that these brain
areas are symmetrical or slightly larger on the right for dyslexic subjects.[11] FMRI imaging studies of
children and young adults reported in 2003 provide further support, demonstrating that increases in age and
reading level are associated with a suppression of right hemispheric activity.[12] [13]
Influenced by the kinesthetic work of Helen Keller and Grace Fernald, and looking for a way to teach reading
using both left and right brain functions,[14] Orton later worked with psychologist and educator Anna
Gillingham to develop an educational intervention that pioneered the use of simultaneous multisensory
instruction. The Orton-Gillingham approach to remedial reading instruction is still widely used and forms the
basis of many reading intervention programs. [15]
In contrast, Dearborn, Gates, Bennet and Blau considered a faulty guidance of the seeing mechanism to be the
cause. The data collected in 1931 by Tinker and Goodenough (The J.Educ. Psych.)(26) seemed to support this
thesis. They sought to discover if a conflict between spontaneous orientation of the scanning action of the eyes
from right to left and training aimed at the acquisition of an opposite direction would allow an interpretation
of the facts observed in the dyslexic disorder and especially of the ability to mirror-read. To this end the
authors asked four adults to read a text reflected in a mirror for ten minutes a day for five months. In all
subjects, the words were not perceived in their globality but required a meticulous analysis of the letters and
syllables. They also demonstrated total or partial inversions even sometimes affecting the order of the words in
a sentence. They revealed a curious impression of not just horizontal but also vertical inversions. These are
errors that exist amongst dyslexics and they suffer from the aggravating circumstance inherent in all learning.
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errors that exist amongst dyslexics and they suffer from the aggravating circumstance inherent in all learning.
What remained to be demonstrated was that there exists a preference amongst dyslexics, without sensory
deficiency, or mental retardation, or any backwardness in speech or language, towards scanning with the eyes
from right to left. Proof of this was provided in a work conducted under Clement Launay in 1949 (thesis G.
Mahec Paris 1951). In adult subjects the reading of a series of 66 tiny lower-case letters, 5 mm high, spaced
5 mm apart, first from left to right and then from right to left was more easily and quickly done in the left to
right direction. For former dyslexic children, a substantial number read a series of 42 letters with equal speed
in both directions and some (10%) read better from right to left than from left to right. The phenomenon is
clearly linked to the dynamics of sight as it disappears when the space between letters is increased,
transforming the reading into spelling. This experience also explains the ability to mirror-read. This reading
test can also be used to diagnose serious cases of dyslexia.
In the 1970s, a new hypothesis, based in part on Orton's theories, emerged that dyslexia stems from a deficit in
phonological processing or difficulty in recognizing that spoken words are formed by discrete phonemes (for
example, that the word CAT comes from the sounds [k], [æ], and [t]). As a result, affected individuals have
difficulty associating these sounds with the visual letters that make up written words. Key studies of the
phonological deficit hypothesis include the finding that the strongest predictor of reading success in school age
children is phonological awareness,[16] and that phonological awareness instruction can improve decoding
skills for children with reading difficulties.[17]
The advent of neuroimaging techniques to study brain structure and function enhanced the research in the
1980s and 1990s. Since then, interest in the neurologically based causes has persisted. Current models of the
relation between the brain and dyslexia generally focus on some form of defective or delayed brain maturation.
More recently, genetic research has provided increasing evidence supporting a genetic origin of dyslexia [18].
Researchers are searching for a link between the neurological and genetic findings, and the reading disorder.
There are many previous and current theories of dyslexia, but one that has much support from research is that,
whatever the biological cause, dyslexia is a matter of reduced phonogical awareness, the ability to analyze and
link the units of spoken and written languages. [19].
Subtypes of developmental dyslexia
Studies by Castles and Coltheart suggest that developmental dyslexia includes at least two prevalent and
distinct varieties or subtypes of dyslexia. Subtypes include surface dyslexia and phonological dyslexia.
Understanding these subtypes is useful in diagnosing learning patterns and developing approaches for
overcoming impairments that may be visual perception impairments or speech discrimination deficits. These
subtypes are based on differing patterns of underlying symptoms, as supported by a finding using large-scale
data from comparative studies of reading patterns in dyslexic and normal readers [20]. In the study by Castles
and Coltheart, 56 dyslexic boys and 56 non-dyslexic boys as a control group were tested. During the test, the
boys read aloud words and non-words that were presented to them. The researchers found that surface
dyslexics (subjects who have poor lexical skills, or can’t make out irregular words well) had a mean difference
of 14.4 words between reading regular words versus irregular words, however, the mean difference in subjects
with phonological dyslexia (subjects who can’t use sub lexical skills, or can’t make out non-words) was only
7.75 words which was comparable to the control group [20]. The majority of their subjects showed signs of
phonological dyslexia. Twenty-nine subjects showed that their non-word reading skills were poorer than their
irregular word reading skills. However, sixteen subjects showed the opposite where their irregular word
reading skills were poorer than their non-word reading skills and were called surface dyslexics [20].
Surface dyslexia
Surface dyslexia is characterized by subjects who can read known words but who have trouble reading words
that are irregular [21]. Surface dyslexia is the outcome of an individual who cannot function using the lexical
procedure for reading out loud. The lexical procedure includes sounding out a word through the use of a past
word already known [20]. In Castles and Coltheart’s study, both control and dyslexic subjects were shown a
card with a word that is irregular or that isn’t pronounced as it looks. Fifteen of the 51 dyslexics were below
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card with a word that is irregular or that isn’t pronounced as it looks. Fifteen of the 51 dyslexics were below
the confidence limit set by the control subjects on ability to read irregular words. These subjects were then
called surface dyslexics [22].
Phonological dyslexia
Phonological dyslexia is characterized by subjects who can read aloud both regular and irregular words but
have difficulties with non-words and with connecting sounds to symbols, or with sounding out words [20].
Phonological processing tasks predict reading accuracy and comprehension. This subtype is the most
predominant form of dyslexia [21]. In Castles and Coltheart’s study, they had 56 dyslexic boys and 56 non-
dyslexic boys read words and non-words given to them. The majority of the boys, 55%, showed a
phonological dyslexic pattern [20].In Castles and Coltheart’s study, dyslexic subjects and control subjects were
asked to read non-words listed on a card, 17 out of 51 cases of dyslexics were below the confidence limit in
non-word reading, which was derived by the control group of subjects their own age. These phonological
dyslexics have a lower non-word reading level than expected by reviewing their irregular word reading level
[22]. Phonological dyslexia is the outcome of a subject who cannot function using the sub lexical
(pronunciations are constructed from smaller orthographic components) procedure for reading out loud [20] .In
Castles and Coltheart’s study, dyslexic and control subjects read words off a note card; the researchers found
that while reading irregular words, the dyslexic subjects scored comparable to the control subjects because sub
lexical skills were not involved in this test [20].
Double deficit dyslexia
Researchers have identified a deficit related to “naming speed”, which relates to the ability of students to
rapidly verbalize the names of symbols such as letters and numbers when tested [23]. In their study, Wolf and
Bowers tested out naming speed by having their subjects name a symbol as quickly as possible when shown on
a flash card. Difficulties in naming speed exist in conjunction with a phonological deficit, is characterized as
double deficit dyslexia. Many parents who are dyslexic will have children who are dyslexic as well.[23].
Variations and related conditions
Dyslexia is a learning disability. It has many underlying causes that are believed to be a brain-based condition
that influences the ability to read written language. It is identified in individuals who fail to learn to read in the
absence of a verbal or nonverbal intellectual impairment, sensory deficit (e.g., a visual deficit or hearing loss),
pervasive developmental deficit or a frank neurological impairment.
The following conditions may also be contributory or overlapping factors, or underlying cause of the dyslexic
symptoms as they can lead to difficulty reading:
Auditory processing disorder is a condition that affects the ability to encode auditory information. It
can lead to problems with auditory working memory and auditory sequencing. Many dyslexics have
auditory processing problems including history of auditory reversals. Auditory processing disorder is
recognized as one of the major causes of dyslexia.
Cluttering is a speech fluency disorder involving both the rate and rhythm of speech, and resulting in
impaired speech intelligibility. Speech is erratic and dysrhythmic, consisting of rapid and jerky spurts
that usually involve faulty phrasing. The personality of the clutterer bears striking resemblance to the
personalities of those with learning disabilities.[24]
Dyspraxia is a neurological condition characterized by a marked difficulty in carrying out routine tasks
involving balance, fine-motor control, and kinesthetic coordination. Problems with short term memory
and organization are typical of dyspraxics. This is most common in dyslexics who also have attention
deficit disorder.
Verbal dyspraxia is a neurological condition characterized by marked difficulty in the use of speech
sounds, which is the result of an immaturity in the speech production area of the brain.
Dysgraphia is a disorder which expresses itself primarily during writing or typing, although in some
cases it may also affect eye-hand coordination in such direction or sequence oriented processes as tying
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knots or carrying out a repetitive task. Dysgraphia is distinct from Dyspraxia in that the person may
have the word to be written or the proper order of steps in mind clearly, but carries the sequence out in
the wrong order.
Dyscalculia is a neurological condition characterized by a problem with learning fundamentals and one
or more of the basic numerical skills. Often people with this condition can understand very complex
mathematical concepts and principles but have difficulty processing formulas and even basic addition
and subtraction.
Scotopic sensitivity syndrome, also known as Irlen Syndrome, is a term used to describe sensitivity to
certain wavelengths of light which interfere with proper visual processing. See also Orthoscopics and
asfedia.
High Functioning Speech Disorder Language is defined as the understanding and use of words and
sentences to convey specific thoughts or meaning in connected speech. Higher-level language abilities
include a person’s ability to conceptualise, manipulate and judge the content and meaning of language.
These skills allow a person to discuss, think and talk about language as an object that can be analysed.
The ability to use these skills requires an underlying understanding of all of the meaningful linguistic units in
language e.g. phonology, syntax, semantics, morphology and pragmatics.
High-level language difficulties, such as High Functioning Speech Disorder, can often affect a person's ability
to summarise information, make inferences, glean the main idea or predict outcomes from language. Quite
often a person can seem quite rigid or concrete in their understanding or use of language, and often lack the
flexibility required to understand humour, sarcasm, multiple meanings or non-literal meanings in language.
A person may have problems in the following areas: • Understanding or using ambiguity. • Understanding or
using humour and sarcasm. • Using a variety of sentence forms to convey the same meaning. • Judging the
appropriateness of words or language units. • Recognising language as a set of individual meaningful units. •
Judging the correct use of grammar. • Segmenting language i.e. or words into sounds and sentences into
words. • Summarising meaning and content either receptively or expressively • Not keeping up with his/hers
peers either academically or socially.
The form of disability may be confused with autistic characteristics or with Asperger’s Syndrome, especially if
social relationships are difficult to make or maintain, or if responses do not appear immediately related to the
question of the context.
Cross-Cultural Incidence Rate Comparison
Catherine McBride-Chang is a researcher in this area.
Scientific research
Theories of developmental dyslexia
The following theories should not be viewed as competing, but viewed as theories trying to explain the
underlying causes of a similar set of symptoms from a variety of research perspectives and background.
Evolutionary hypothesis
This theory posits that reading is an unnatural act, and carried out by humans for an exceedingly brief period
in our evolutionary history (Dalby, 1986). It has been less than a hundred years that most western societies
promoted reading by the mass population and therefore the forces that shape our behavior have been weak.
Many areas of the world still do not have access to reading for the majority of the population. There is no
evidence that "pathology" underlies dyslexia but much evidence for cerebral variation or differences. It is these
essential differences that are taxed with the artificial task of reading. [25] The native reading hypothesis of
dyslexia is another evolutionary theory which argues that because spoken language is naturally learned in the
first few years of development, similarly, written language is best learned at the same early age. It suggests that
many forms of dyslexia are therefore, to some extent, a result of introducing reading too late in
neurodevelopment. This means that the typically late reading of dyslexics might sometimes be the cause of
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neurodevelopment. This means that the typically late reading of dyslexics might sometimes be the cause of
dyslexia, rather than the other way around, and many cases of dyslexia might be prevented by the earlier
introduction of reading instruction.[26]
Phonological hypothesis
The phonological hypothesis postulates that dyslexics have a specific impairment in the representation, storage
and/or retrieval of speech sounds. It explains dyslexics' reading impairment on the basis that learning to read
an alphabetic system requires learning the grapheme/phoneme correspondence, i.e. the correspondence
between letters and constituent sounds of speech. If these sounds are poorly represented, stored or retrieved,
the learning of grapheme/phoneme correspondences, the foundation of reading by phonic methods for
alphabetic systems, will be affected accordingly.[27]
Rapid auditory processing theory
The rapid auditory processing theory is an alternative to the phonological deficit theory, which specifies that
the primary deficit lies in the perception of short or rapidly varying sounds. Support for this theory arises from
evidence that dyslexics show poor performance on a number of auditory tasks, including frequency
discrimination and temporal order judgment. Backward masking tasks, in particular, demonstrate a 100-fold
(40 dB) difference in sensitivity between normals and dyslexics. [28] Abnormal neurophysiological responses
to various auditory stimuli have also been demonstrated. The failure to correctly represent short sounds and
fast transitions would cause further difficulties in particular when such acoustic events are the cues to
phonemic contrasts, as in /ba/ versus /da/. There is also evidence that dyslexics may have poorer categorical
perception of certain contrasts.[27]
Visual theory
The visual theory (Lovegrove et al., 1980; Livingstone et al., 1991; Stein and Walsh, 1997) reflects another
long standing tradition in the study of dyslexia, that of considering it as a visual impairment giving rise to
difficulties with the processing of letters and words on a page of text. This may take the form of unstable
binocular fixations, poor vergence, or increased visual crowding. The visual theory does not exclude a
phonological deficit, but emphasizes a visual contribution to reading problems, at least in some dyslexic
individuals. At the biological level, the proposed etiology of the visual dysfunction is based on the division of
the visual system into two distinct pathways that have different roles and properties: the magnocellular and
parvocellular pathways. The theory postulates that the magnocellular pathway is selectively disrupted in certain
dyslexic individuals, leading to deficiencies in visual processing, and, via the posterior parietal cortex, to
abnormal binocular control and visuospatial attention. Evidence for magnocellular dysfunction comes from
anatomical studies showing abnormalities of the magnocellular layers of the lateral geniculate nucleus
(Livingstone et al., 1991), psychophysical studies showing decreased sensitivity in the magnocellular range,
i.e. low spatial frequencies and high temporal frequencies in dyslexics, and brain imaging studies.[27]
Cerebellar theory
Yet another view is represented by the automaticity/cerebellar theory of dyslexia. Here the biological claim is
that the dyslexic's cerebellum is mildly dysfunctional and that a number of cognitive difficulties ensue. First,
the cerebellum plays a role in motor control and therefore in speech articulation. It is postulated that retarded
or dysfunctional articulation would lead to deficient phonological representations. Secondly, the cerebellum
plays a role in the automatization of overlearned tasks, such as driving, typing and reading. A weak capacity to
automatize would affect, among other things, the learning of grapheme-to-phoneme correspondences. Support
for the cerebellar theory comes from evidence of poor performance of dyslexics in a large number of motor
tasks, in dual tasks demonstrating impaired automatization of balance, and in time estimation, a non-motor
cerebellar task. Brain imaging studies have also shown anatomical, metabolic and activation differences in the
cerebellum of dyslexics.[27]
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Magnocellular theory
There is a unifying theory that attempts to integrate all the findings mentioned above. A generalization of the
visual theory, the magnocellular theory postulates that the magnocellular dysfunction is not restricted to the
visual pathways but is generalized to all modalities (visual and auditory as well as tactile). Furthermore, as the
cerebellum receives massive input from various magnocellular systems in the brain, it is also predicted to be
affected by the general magnocellular defect (Stein et al., 2001). Through a single biological cause, this theory
therefore manages to account for all known manifestations of dyslexia: visual, auditory, tactile, motor and,
consequently, phonological. Beyond the evidence pertaining to each of the theories described previously,
evidence specifically relevant to the magnocellular theory includes magnocellular abnormalities in the medial
as well as the lateral geniculate nucleus of dyslexics' brains, poor performance of dyslexics in the tactile
domain, and the co-occurrence of visual and auditory problems in certain dyslexics.[27]
Perceptual visual-noise exclusion hypothesis
The concept of a perceptual noise exclusion (Visual-Noise) deficit is an emerging hypothesis, supported by
research showing that dyslexic subjects experience difficulty in performing visual tasks such as motion
detection in the presence of perceptual distractions, but do not show the same impairment when the distracting
factors are removed in an experimental setting.[29] The researchers have analogized their findings concerning
visual discrimination tasks to findings in other research related to auditory discrimination tasks. They assert
that dyslexic symptoms arise because of an impaired ability to filter out both visual and auditory distractions,
and to categorize information so as to distinguish the important sensory data from the irrelevant.[30]
Research using functional brain scan technology
A University of Hong Kong study argues that dyslexia affects different structural parts of children's brains
depending on the language which the children read.[31] The study focused on comparing children that were
raised reading English and children raised reading Chinese. Using MRI technology researchers found that the
children reading English used a different part of the brain than those reading Chinese. Researchers were
surprised by this discovery and hope that the findings will help lead them to any neurobiological cause for
dyslexia.[31]
Research also indicates
Genetic factors
A familial component to reading disorders was identified in the 1950s, and twin studies beginning in the early
1980s onward suggest that reading ability and disability is a heritable trait. Molecular studies have since linked
several forms of dyslexia to genetic markers.[32] [33] [34].
Genetic research in families and twins with dyslexia have identified over nine chromosome regions as being
associated with susceptibility to dyslexia. As is common in complex genetics, several of studies have not yet
been replicated. [35]
However, several candidate genes have been identified, including at the two regions first related to dyslexia:
DCDC2 [36] and KIAA0319 on chromosome 6, and DYX1C1 on chromosome 15.
Physiology
Modern neuroimaging techniques such as functional Magnetic Resonance Imaging (fMRI) and Positron
Emission Tomography (PET) have produced clear evidence of structural differences in the brains of children
with reading difficulties. It has been found that people with dyslexia have a deficit in parts of the left
hemisphere of the brain involved in reading, which includes the inferior frontal gyrus, inferior parietal lobule,
and middle and ventral temporal cortex.[37] [38]
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Scientific studies of brains donated to medical research have revealed that there are anatomical differences in
two parts of the dyslexic brain: the cerebral cortex and the thalamus. In 1979 Albert Galaburda of Harvard
Medical School noticed anatomical differences in the language center in a dyslexic brain, showing
microscopic differences known as ectopias and microgyria. Both affect the typical six-layer structure of the
cortex. An ectopia is a collection of neurons that have pushed up from the lower layers of the cortex into the
outermost one. A microgyrus is an area of cortex that includes only four layers instead of six. These
differences affect connectivity and functionality of the cortex in critical areas related to auditory processing
and visual processing, which seems consistent with the hypothesis that dyslexia stems from a phonological
awareness deficit.
Studies of both autopsied brains and living brains using neuroimaging techniques have shown that the brains
of dyslexic children are symmetrical, unlike the asymmetrical brains of non-dyslexic readers who had larger
left hemispheres.[39]
Scientists do not claim that all people with dyslexia have these structural brain differences. However, the
studies are evidence that some children's reading problems are brain based. The challenge for researchers is to
determine how these structural differences affect reading acquisition. [40]
Effect of language orthography
Some studies have concluded that speakers of languages whose orthography has a highly consistent
correspondence between letter and sound (e.g., Italian) suffer less from the effects of dyslexia than speakers of
languages where the letter-sound correspondence is less consistent (e.g. English and French).[41]
In one of these studies, reported in Seymour et al.,[42] the word-reading accuracy of first-grade children of
different European languages was measured. English children had an accuracy of just 40%, whereas among
children of most other European languages accuracy was about 95%, with French and Danish children
somewhere in the middle at about 75%; Danish and French are known to have an irregular pronunciation.
However, this does not mean that dyslexia is caused by orthography: instead, Ziegler et al.[43] claim that the
dyslexia suffered by German or Italian dyslexics is of the same kind as the one suffered by the English ones,
supporting the theory that the origin of dyslexia is biological. In a study by Paulescu et al. (Science, 2001)
English, French, and Italian dyslexics were found to have the same brain function signature when studied with
functional magnetic resonance imaging (fMRI), a signature that differed from non-dyslexic readers. However,
dyslexia has more pronounced effects on orthographically difficult languages, e.g., dyslexics have more
difficulty in English than Italian. Modern theories of some forms of dyslexia uses orthography to test a
hypothesis of psychological causation
Characteristics
Formal diagnosis of dyslexia is made by a qualified professional, such as a neurologist or an educational
psychologist. Evaluation generally includes testing of reading ability together with measures of underlying
skills such as tests of rapid naming, to evaluate short term memory and sequencing skills, and nonword reading
to evaluate phonological coding skills. Evaluation will usually also include an IQ test to establish a profile of
learning strengths and weaknesses. However, the use of a "discrepancy" between full scale IQ and reading
level as a factor in diagnosis has been discredited by recent research.[44] It often includes interdisciplinary
testing to exclude other possible causes for reading difficulties, such as a more generalized cognitive
impairment or physical causes such as problems with vision or hearing.
Recent advances in neuroimaging and genetics provide evidence that could potentially help identify children
with dyslexia before they learn to read in the future. However, such tests have not yet been developed and
more research is needed before such testing could be considered reliable.
Speech, hearing and listening
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Speech delays may be an early warning sign of dyslexia. Many dyslexics may have problems processing and
decoding auditory input prior to reproducing their own version of speech. Early stuttering or cluttering can
also be warning signs of dyslexia.
Many dyslexics also can have problems with speaking clearly. They can mix up sounds in multi-syllabic
words (ex: aminal for animal, bisghetti for spaghetti, hekalopter for helicopter, hangaberg for hamburger,
ageen for magazine, etc.) They can also have problems speaking in full sentences. They can have trouble
correctly articulating Rs and Ls as well as Ms and Ns. They often have "immature" speech. They may still be
saying "wed and gween" instead of "red and green" in second or third grade. Many dyslexics might have
speech therapy in special education. They may have fast speech, cluttered speech, or hesitant speech. [45] [46]
Reading requires the sounding out of words. Therefore, it makes sense that children with speech problems can
end up having reading problems later. Many have problems with speech due to problems with auditory
processing disorder issues.
Many dyslexics have problems with phonemic awareness. Phonemes are the smallest units in spoken language.
The Auditory related underlying causes of dyslexia may be partially remediated by auditory therapy or speech
therapy, which help with phonemic awareness. This may help to make sense of phonics which may help with
phonological awareness, which is needed to sound out words.
Many acquire auditory processing disorder as an underlying cause of dyslexia from glue ear, otitis media.
Some shared symptoms of the speech/hearing deficits and dyslexia:
1. Confusion with before/after, right/left, and so on
2. Difficulty learning the alphabet
3. Difficulty with word retrieval or naming problems
4. Difficulty identifying or generating rhyming words, or counting syllables in words (phonological
awareness)
5. Difficulty with hearing and manipulating sounds in words (phonemic awareness)
6. Difficulty distinguishing different sounds in words (auditory discrimination)
7. Difficulty in learning the sounds of letters
8. Difficulty associating individual words with their correct meanings
9. Difficulty with time keeping and concept of time
10. Confusion with combinations of words
11. Due to fear of speaking incorrectly, some children become withdrawn and shy or become bullies out of
their inability to understand the social cues in their environment
12. Difficulty in organization skills
The identification of these factors results from the study of patterns across many clinical observations of
dyslexic children. In the UK, Thomas Richard Miles was important in such work and his observations led him
to develop the Bangor Dyslexia Diagnostic Test. [47]
Reading and spelling
Spelling errors — Because of difficulty learning letter-sound correspondences, individuals with dyslexia
might tend to misspell words, or leave vowels out of words.
Letter order - Dyslexics may also reverse the order of two letters especially when the final, incorrect,
word looks similar to the intended word (e.g., spelling "dose" instead of "does").
Letter addition/subtraction - Dyslexics may perceive a word with letters added, subtracted, or repeated.
This can lead to confusion between two words containing most of the same letters.
Highly phoneticized spelling - Dyslexics also commonly spell words inconsistently, but in a highly
phonetic form such as writing "shud" for "should". Dyslexic individuals also typically have difficulty
distinguishing among homophones such as "their" and "there".
Vocabulary - Having a small written vocabulary, even if they have a large spoken vocabulary.
Writing and motor skills
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Because of literacy problems, an individual with dyslexia may have difficulty with handwriting. This can
involve slower writing speed than average, poor handwriting characterised by irregularly formed letters, or
inability to write straight on a blank paper with no guideline.
Some studies have also reported gross motor difficulties in dyslexia, including motor skills disorder. This
difficulty is indicated by clumsiness and poor coordination. The relationship between motor skills and reading
difficulties is poorly understood but could be linked to the role of the cerebellum and inner ear in the
development of reading and motor abilities.[48]
Mathematical abilities
Dyslexia should not be confused with dyscalculia, a learning disability marked by severe difficulties with
mathematics. Individuals with dyslexia can be gifted in mathematics while having poor reading skills.
However, in spite of this they might have difficulty with word problems (i.e., descriptive mathematics,
engineering, or physics problems that rely on written text rather than numbers or formulas). Individuals with
dyslexia may also have difficulty remembering mathematical facts, such as multiplication tables, learning the
sequence of steps when performing calculations, such as long division, and other mathematics which involve
remembering the order in which numbers appear. This may be exhibited by having a slow response in
mathematical drills and difficulty with word problems.
Adaptive attributes
A study has found that entrepreneurs are five times more likely to be dyslexic than average citizens[49]. There
also exists a movement concerning the idea that dyslexia can be a natural neurological variation and a useful
set of traits when dealing with large and complex bodies of information. This was first described and promoted
in Thomas G. West's 1991 book, In the Mind's Eye: Visual Thinkers, Gifted People with Dyslexia and Other
Learning Difficulties, Computer Images and the Ironies of Creativity
.
Management
See also: Dyslexia treatment
There is no cure for dyslexia, but dyslexic individuals can learn to read and write with appropriate education
or treatment. There is wide research evidence indicating that specialized phonics instruction can help
remediate the reading deficits. The fundamental aim is to make children aware of correspondences between
graphemes and phonemes, and to relate these to reading and spelling. It has been found that training, that is
also focused towards visual language and orthographic issues, yields longer-lasting gains than mere oral
phonological training.[19]
Teachers are also using audiobooks as a way of teaching textbooks in an engaging way to those with dyslexia.
In the UK, one of the biggest charities is Listening Books, offering members a streaming service over the
internet. www.listening-books.org.uk An Australian company, ReadHowYouWant is working to make all
published books available in audiobook form[50].
Accessible publishing, the method by which charities and companies work to provide books and textbooks in a
variety of formats and fonts suitable for all readers, has long been focused on developing formats to improve
dyslexia by use of word patterns, phonic symbols, highlighting mirrored letters (such as b and d), and
increasing the font size as words move along[51].
Effective training is given by teachers at school or kindergarten. Meta-analysis evaluating the effects of
phonological awareness instruction has shown that word reading skills of all children, those with a risk for
reading problems as well as those developing typically, improved their reading in systematic phonics
instruction, a method that encourages a word to be recognised through the building of its constituent sounds.
Basic phonemic awareness instruction did not, however, improve spelling in disabled readers.[52] None of the
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