Dyslexia or developmental reading disorder is known as a reading disability and is characterized by difficulties in word recognition. The World Federation of Neurology defines dyslexia as "a disorder manifested by difficulty in learning to read despite conventional instruction, adequate intelligence and sociocultural opportunity". The National Institute of Neurological Disorders defines dyslexia as "...a brain-based type of learning disability that specifically impairs a person's ability to read". The condition occurs when there is a problem in parts of the brain that aid in the interpretation of language. Dyslexics are often reluctant and slow readers, and spelling presents a special challenge for them. The "acid test" for dyslexia is a "non-words" reading test or a list of "made up" words that cannot be "guessed at." In the same way, a "non-word" spelling test (a measure of phonological awareness) is a useful tool to identify dyslexia. The idea behind "non-word" tests is that the person being tested must rely on his/her phonological processing skills in order to read or spell words. They cannot rely on prior knowledge of words as some dyslexics have excellent visual memory and often resort to memorizing word shapes to get through their reading and spelling tests. Those with dyslexia can have a range of IQs and as such, the reliance of an IQ achievement discrepancy in the diagnosis of dyslexia is not recommended.
What are the signs of dyslexia?
General problems associated with dyslexia
Early symptoms that correlate with a dyslexia diagnosis include a delay in speech, letter reversal or mirror writing and being distracted by background noise. A common misconception about dyslexia is that all dyslexics write backwards or move letters around when reading; in fact, this occurs in only a very small percentage of dyslexics. The problems displayed by individuals with dyslexia often involve difficulties in acquiring and using language; reading and writing letters may be in the wrong order but are just one manifestation and will not occur in all cases. Other problems experienced by dyslexics are:
Learning to speak
Organizing written and spoken language
Learning letters and their sounds
Memorizing number facts
Learning a foreign language
Correctly doing math operations
Not all students who have difficulties with these skills are dyslexic. Formal testing is the only way to confirm a diagnosis of suspected dyslexia. Several learning disabilities may occur with dyslexia, but it is not clear whether these disabilities are related to the underlying causes of dyslexia or completely separate.
Resources for medical professionals
Researchers have been trying to identify the biological basis of dyslexia since it was first described by Oswald Berkhan in 1881. The term dyslexia was coined in 1887 by Rudolf Berlin. Theories of etiology have evolved with each new generation of researchers and recent theories tend to enhance one or more of the older theories as understanding of the nature of dyslexia evolves.