This paper describes and discusses acquired and developmental dyslexia. Topics covered include neurological and etiological bases as well as remediative and instructional strategies.
Dyslexia: History, Definition, Relation to Normal Reading
Richardson (1992) has noted that much of the foundational work on dyslexia came from studies conducted in the first half of the century by physicians on people with diverse forms of brain damage. Originally dyslexia was considered to be a type of aphasia. However, Richardson states that it was also referred to as "word blindness" defined as the inability to interpret written or printed language despite normal vision. Richardson further reports that while the dyslexic condition had been postulated for years as related to brain defect or damage, it was not until 1979 that physical evidence of abnormal cell structure within the brain was actually found.
Kamhi (1992) has noted that the study of dyslexia has been "plagued" by definitional inadequacy. However, he notes that most researchers and educators agree that the condition is best defined as a developmental language disorder involving a life-long, possibly genetic, difficulty processing phonological information.
This difficulty involves encoding, retrieving, and using phonological codes in memory, as well as deficits in phonological awareness and speech production. A prominent characteristic of the disorder is spoken and written language deficiency. What distinguishes this definition from earlier definitions is that it focuses on the condition as a learning problem and does not assume the problem to be specific to reading.
Relation to Normal Reading Processes
As defined in the public schools, reading involves a set of sequenced skills that can be divided into three phases: (1) the development of readiness skills (e.g. left-to-right sequencing, visual and auditory discrimination skills, and memory skills); (2) word recogni...