Dyslexia literally means the inability to master language. In practice, however, the term refers to people who have extreme difficulty acquiring the ability to read and spell. Specifically, people with dyslexia have trouble learning the code for written language. Difficulty in sounding out words and spelling words persists, despite effort on the part of teachers and the learner. The person with dyslexia demonstrates a number of characteristics associated with difficulty learning to read and write.
No generally accepted definition of dyslexia exists in the world! However, research findings over the past 25 years, in countries around the world, led to development of a descriptive definition that guides the work of the Tennessee Center for the Study and Treatment of Dyslexia. By describing what dyslexia is, the Center is able to assure accurate identification and focused treatment.
The Center for Dyslexia defines dyslexia as:
A language-based learning disorder that is biological in origin and primarily interferes with the acquisition of print literacy (reading, writing, and spelling). It is characterized by poor decoding and spelling abilities as well as deficits in phonological awareness and/or manipulation. These primary characteristics may co-occur with spoken language difficulties and deficits in short-term memory. Secondary characteristics may include poor reading comprehension (due to decoding and memory difficulties) and poor written expression as well as difficulty organizing information for study and retrieval.
(Sawyer, August 1993)
Dyslexia is found in families across the full range of socioeconomic backgrounds in society.
Only recently has a definition of dyslexia been adopted as a working definition by the National Institute for Child Health and Human Development:
"Dyslexia is a specific learning disability that is neurologicalin origin.It 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 phonological 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 growth of vocabulary and background knowledge.";
Adopted by the IDA Board of Directors, Nov. 12, 2002. This Definition is also used by the National Institute of Child Health and Human Development (NICHD).
The most common form of dyslexia is associated with the phonological core deficit referred to in the definitions above. People with this disability have extreme difficulty isolating and sequencing syllables and sounds in words. At the syllable level, this results in mixing up the order of syllables in a word or omitting a syllable -- saying or writing "intimate" for "imitate", "agate" for "applegate", "Willim for William", "intivation" for "invitation". At the sound (phoneme) level, the phonological core deficit results in extreme difficulty learning to pair letters of the alphabet with speech sounds (referred to as acquiring the alphabetic principle) and sequencing letters or sounds to produce words. For example, saying or writing "lello" for "yellow", writing "hlep" for "help", saying "patter" for "platter", writing "cooper" for "copper".