Research studies into dyslexia can be dated as far back as the late 19th century. However, it was not until fifty years ago that the term dyslexia came into use. Originating from the Greek words dys, meaning difficulty, and lexia, meaning words; dyslexia is a learning disability that affects the sufferer’s ability to read, write and spell. There are two main types of dyslexia: acquired and developmental dyslexia. Acquired dyslexia, also known as aphasia, is a direct result of injury to the brain.
A common cause of this type of injury is a stroke. In this instance, the blood flow to the brain is disrupted, leaving the person with language problems; including speech and word recognition. Developmental dyslexia is not as clear cut. There are three main thoughts on what the cause of developmental dyslexia could be. Firstly, is the idea that this form of dyslexia occurs even before birth; and that it is due to genetic inheritance. The work of B Hallgren would appear to substantiate this claim.
Hallgren reported that from a sample of 276 dyslexic cases, 88% of them had at least one relative who also experienced reading difficulties. He also looked at the developmental similarities between identical twins. Since identical twins are produced from the same zygote, both twins should have the same genetic makeup. Hallgren considered twelve pairs of identical twins; and found that both of the twins within the pair had the same learning difficulties. It has also been presented that hearing problem from an early age could lead to dyslexia.
When a young child repeatedly suffers from colds and throat infections, their ears can become temporarily blocked. This in turn can affect the brain’s ability to relate to the sounds it hears. The early ability to learn sounds and words is considered to be essential in the later development of language. Therefore, it is believed that if the child’s hearing impairment continues unnoticed, it is likely that the child will gain problems in processing auditory information; which may lead onto to dyslexia.
In 1978, Mattis found that 86% of the dyslexics he studied had a considerable difficulty in linking a spoken word to its written form; and concluded that a deficit in auditory language processing was a major factor in dyslexia. The latest theory is that developmental dyslexia is a result of abnormalities found in the cerebellum of the brain. A study in 2001 looked at the brain activity of six dyslexic and six non-dyslexic adults. Both groups were shown a sequence of right-handed finger movements.
Each person’s brain activity was monitored using positron emission tomography (PET) while they repeated the shown sequence; and were shown a new sequence to learn. The results of the study, led by Prof. Rod Nicholson, showed that there was a difference in the activity in the right cerebellum between the dyslexic and non-dyslexic adults. In fact, the adults with dyslexia showed less activity in this area than the adults without dyslexia. Gender and environment have been among other factors considered to have an effect.
The idea that dyslexia is more common in boys than in girls has been a long running one. From the results found from 19 different surveys between 1927 and 1968, M. Critchley concluded that boys were four times more likely to suffer from dyslexia than girls. A recent survey, by the British Dyslexia Association, has also shown that three times as many boys as girls receive extra tuition for their dyslexia. However, there has been no evidence to suggest that boys suffer from dyslexia any more severely than girls. There has also been no solid proof to imply that dyslexia is linked to the child’s environment.
In reality, dyslexia has been found to occur within all ranges of intellectual abilities; and has been proven to be independent of cultural and emotional stimuli. “On a visit to China I felt outside society. I couldn’t understand the written codes around me. Then I understood what it felt like to be severely dyslexic. ” – Liz Brooks, former Executive Director of the Dyslexia Institute U. K There is a preconception among many that dyslexia only affects the sufferer’s ability to read. It is true, that dyslexic children may be late in learning to read and are more likely to be slow readers.
However, many dyslexics can read well; and many people who are poor readers are not dyslexic. For a lot of older children and adults, reading will not necessarily be the major problem. A more common, continuing problem is writing and spelling. For example, a dyslexic person may leave letters out of words or put the letters round the wrong way: so that ‘b’ is used for’d’; ‘was’ becomes ‘saw’; and ‘gorgus’ is used to represent gorgeous. It is also possible that a sufferer may use complete mirror writing, in instances where they have no strong right or left handed dominance.
Other accompanying problems may include: difficulties in remembering and working with symbols, for example numerical calculation; difficulty in reading and writing words with several syllables, for example ‘philosophical’; and they may have a poor short-term memory , which in turn can result in difficulty recall letters, numbers and sequences. Some non-language indicators can be: poor concentration; having difficulty in differentiating between left and right; having problems repeating the order of the days and months; and having difficulty in tying shoe laces and ties.