What is Dyslexia?

A lot of energy has gone into defining dyslexia over the last few years, and I'm sure the arguments aren't over yet. Here is the definition that the International Dyslexia Association (IDA) adopted in 1994. (Back then the IDA was still called The Orton Dyslexia Society.) I have copied it from "Toward a Definition of Dyslexia" by G. Reid Lyon in Annals of Dyslexia, Volume XLV, 1995, pp. 3-27. That article interprets the definition in some detail, and describes some of the controversies surrounding the issue.

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.

Of course, if you are trying to figure out whether somebody is dyslexic, a definition like the one above is not much help. You want a list of symptoms. You can find one on the Dyslexia Fact Sheet of the Learning Disabilities Association of America. There is another one on the IDA web site.

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Everything on this web site is the personal opinion of S. W. Davison. Any of it might be incorrect or out-of-date.