A general term for a number of disorders relating to problems with —primarily— the written language. There are different types of dyslexia with different causes. Clinical (treatment) experience shows that it is wrong to 'wait and see' with dyslexia in a child. If nothing is done to treat it, slowness in learning to read can soon become a serious reading disability.
Dyslexia was first pinpointed in 1887. The term was used for people whose language skills were considerably lower than expected considering their intelligence. Research has shown that dyslexia has a neurological cause. Even though there are numerous variations and causes, dyslexia often entails an inability to interpret visual or auditory information adequately. The brain has various ways of compensating this to some extent (or, with mild dyslexia, fully) by applying other brain functions. This will depend on the severity of the disorder. On average, a dyslexic person uses 10 times more brain capacity when processing language-related information than a normal person. Stimulation and training of the brain at an early age can result in improved compensation. Dyslexia mainly affects reading proficiency, spelling and vocabulary, but can also affect hearing, speech, writing and handwriting.
Dyslexia proves largely to be family-related. Moreover, family members of dyslectics often have other language problems. Dyslexia is more common among boys than girls and there are strong indications that it is hereditary. The probability of a boy being dyslexic can be as high as 50% if his father is too. The percentage with girls is a little lower. Results of large-scale studies involving twins suggest that the feeling for speech sounds, measured by testing rhyming skills, correlates with phonological reading skills.
Dyslexia is a development disorder affecting people of all ages, but symptoms vary with age. Studies involving children with a hereditary risk of dyslexia have reported difficulties with speech production and grammatical development at the age of 30 months, followed by slower vocabulary acquisition during pre-school years, culminating in delayed phonological development and alphabet knowledge in young schoolchildren. Epidemiological studies make frequent reference to parents reporting delayed speech and language among children with reading difficulties.
The most comprehensive picture of dyslexia can be obtained from school-going children. Although speech perception is intact in most cases, dyslexic children have problems thinking about the sound structure of spoken words. Phonological problems of this type make it difficult to learn how to relate sounds to the letters of printed words. Most dyslexic children have problems with a phonetic approach to reading, and when spelling they cannot reproduce the sound structure of words. Although dyslexic children overcome many of their problems, they have subtle (slight) problems with phonological awareness and reading and writing proficiency during adulthood. Functional brain research is helping us to understand why: when dyslexic adults are asked whether words rhyme or they have to perform verbal, short-term memory tasks, it transpires that they only use part of the brain area that would normally be involved. That may well mean that their phonological problems are the result of a weak link between the language areas at the anterior and posterior parts of the left cerebral hemisphere.
Although the term 'dyslexia' is currently under discussion, there are very strong indications that unexpected reading difficulties among children are caused by language deficiencies in the phonological area. Children with reading difficulties often have a variety of psychosomatic problems: headaches and difficulties in seeing are common. A detailed description of the case and the family background can uncover dyslexia problems. Routine assessment of pre-school children can easily discover how familiar they are with nursery rhymes and letters.