Dyslexia is the most common learning disability. It is defined by the International Dyslexia Association as: a specific learning disability that is neurological in origin. Dyslexia is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities.
These difficulties typically result from a deficit in the phonologic component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede the growth of vocabulary and background knowledge.
Someone with dyslexia has trouble reading and writing even though he or she has the intelligence and motivation needed to learn to read. Although people with dyslexia have trouble understanding words they read, they usually can understand the same words when they are read aloud by another person.
Researchers don't know exactly what causes dyslexia, but they think a problem during development may affect the way the brain processes information. They also believe that genetics (inheritance) plays a part. Although a gene for dyslexia has not been found, dyslexia does tend to run in families. Dyslexia is not caused by a physical disability, such as vision or hearing problems. Many people with dyslexia have average or above average intelligence. Basically, the brains of people with dyslexia have a hard time receiving, organizing, remembering or using information.
In the United States, approximately 5% to 10% of the population probably has some sort of dyslexia.