Dyslexia
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Dyslexia is a syndrome: a collection of associated characteristics that vary in degree and from person to person. These characteristics encompass not only distinctive clusters of problems but sometimes also distinctive talents. Professor Tim Miles comments that dyslexia is typically characterised by ‘an unusual balance of skills’.
The syndrome of dyslexia is now widely recognised as being a specific learning disability of neurological origin that does not imply low intelligence or poor educational potential, and which is independent of race and social background.
Although dyslexia seems to be more prevalent amongst males than females, the exact ratio is unknown: the most commonly quoted figures are between 3:1 and 5:1. The evidence suggests that in at least two-thirds of cases, dyslexia has a genetic cause, but in some cases birth difficulties may play an aetiological role.
Dyslexia may overlap with related conditions such as dyspraxia, attention deficit disorder (with or without hyperactivity) and dysphasia. In childhood, its effects can be mis-attributed to emotional or behavioural disorder. By adulthood, many dyslexics will have developed sophisticated compensating strategies that may mask their difficulties.
The majority of experts concur that about 4% of the population are affected to a significant extent. This figure is based on the incidence of pupils who have received normal schooling and who do not have significant emotional, social or medical aetiology, but whose literacy development by the end of the primary school is more than 2 years behind levels which would be expected on the basis of chronological age and intelligence. However, perhaps as many as a further 6% of the population may be more mildly affected (e.g. in spelling).
The neurological bases of dyslexia are now well established and reflected in current definitions of the condition. For example, the International Dyslexia Association (formerly the Orton Dyslexia Society) published the following definition of dyslexia:
“Dyslexia is a neurologically-based, often familial disorder which interferes with the acquisition of language. Varying in the degrees of severity, it is manifested by difficulties in receptive and expressive language, including phonological processing, in reading, writing, spelling, handwriting and sometimes arithmetic. Dyslexia is not the result of lack of motivation, sensory impairment, inadequate instructional or environmental opportunities, but may occur together with these conditions. Although dyslexia is lifelong, individuals with dyslexia frequently respond successfully to timely and appropriate intervention” (Orton Dyslexia Society, 1994).
The biology of dyslexia has been investigated in a range of studies that have confirmed a difference in brain anatomy, organisation and functioning. Research has also shown that the effects of dyslexia are due - at least, in part - to heritable influences. The latest brain imaging techniques, as well as encephalographic recording of the electrical activity of the brain, and even post-mortem examination, all reveal a range of functional and structural cerebral anomalies of persons with dyslexia.
Although it is a disability, dyslexia is not a ‘disease’ nor can it be ‘cured’. Indeed, the neurological differences found in dyslexia may confer advantages for some individuals (e.g. in visual or perceptual skills), which may to some extent explain the apparent paradox that some individuals who have problems with elementary skills such as reading and writing can nevertheless be highly gifted in other areas.
The deficit model of dyslexia is now steadily giving way to one in which dyslexia is increasingly recognised as a difference in cognition and learning.
The following cognitive characteristics of dyslexia have been widely noted in connection with dyslexia:
* A marked inefficiency in the working or short-term memory system
* Inadequate phonological processing abilities
* Difficulties with motor skills or co-ordination
* A range of problems connected with visual processing
Main educational effects of dyslexia
Reading and perceptual difficulties
These can include:
* early difficulties in acquiring phonic skills
* a high proportion of errors in oral reading
* difficulty in extracting the sense from written material without substantial rereading
* slow reading speed
* inaccurate reading, omission of words
* frequent loss of the place when reading
* an inability to skim through or scan over reading matter
* a high degree of distractibility when reading
* perceived distortion of text (words may seem to float off the page or run together)
* a visually irritating glare from white paper or white-boards
Writing problems
These can include:
* an intractable spelling problem, often concealed by the use of an automatic spell-checker
* confusion of small words such as which/with
* omission of words, especially when the writer is under pressure
* awkward handwriting and/or slow writing speed
* an unexpected difference between oral and written expression, with oral contributions being typically of a much higher quality than written accounts of the same subject matter in terms of structure, self expression and correct use of words.