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This paper elaborates on the components of a working definition of developmental dyslexia. It follows the general format of a paper by Lyon published in Annals of Dyslexia in 1995, which elaborated on a working definition proposed in 1994 (Lyon, 1995). The current definition agreed on by the work group updates and expands on the working definition from 1994.
In addition to the authors, members of the working group of the International Dyslexia Association included Susan Brady, Hugh Catts, Emerson Dickman, Guinevere Eden, Jack Fletcher, Jeffrey Gilger, Robin Morris, Harley Tomey, and Thomas Viall.
CURRENT DEFINITION-2003
Dyslexia is a specific learning disability that is neurobiological in 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.
WORKING DEFINITION FROM 1994
Dyslexia is one of several distinct learning disabilities. It is a specific language-based disorder of constitutional origin characterized by difficulties in single word decoding, usually reflecting insufficient phonological processing. These difficulties in single word decoding are often unexpected in relation to age and other cognitive and academic abilities; they are not the result of generalized developmental disability or sensory impairment. Dyslexia is manifest by variable difficulty with different forms of language, often including, in addition to problems with reading, a conspicuous problem with acquiring proficiency in writing and spelling.
Dyslexia is a specific learning disability. This opening sentence identifies dyslexia as a specific learning disability in contrast to the more general term learning disabilities (LD). While the general LD category encompasses a wide range of disorders in listening, speaking, reading, writing, and mathematics (USOE, 1977), we continue to recommend (Fletcher et al., 2002; Lyon, 1995) that the field should discontinue the use of the broad term learning disabilities when discussing reading disabilities, and should instead discuss specific disabilities defined in terms of coherent and operational domains. From an epidemiologic perspective, reading disabilities affect at least 80 percent of the LD population and thus constitute...