Shaywitz, Bennett A. Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut.
Shaywitz, Sally E. Yale University School of Medicine, New Haven, Connecticut.
Last reviewed:March 2021
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- Neurologic basis
- Risk factors
- Related Primary Literature
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Impairment of the ability to read. Developmental dyslexia, which is a learning disorder with a neurobiological basis, is characterized by unexpected difficulty in reading in children and adults who otherwise possess the intelligence and motivation considered necessary for accurate and fluent reading. Dyslexia is one of the most common problems affecting children and adults. For example, in the United States, the prevalence of dyslexia is estimated to range from 5% to 17% of school-age children (see illustration), with as many as 40% reading below grade level. It is the most common and most carefully studied of the learning disabilities, affecting at least 80% of all individuals identified as learning-disabled. Epidemiologic data indicate that dyslexia fits a dimensional model—within the population, reading ability occurs along a continuum, with reading disability representing the tail of a normal distribution. Further evidence based on sample surveys of randomly selected populations of children indicates that dyslexia affects boys and girls comparably. (The long-held belief that only boys suffer from dyslexia reflected bias in school-identified samples.) Dyslexia is a persistent, chronic condition that stays with the individual for a lifetime. It is both familial and heritable; about half of children who have a parent with dyslexia may have the disorder. See also: Cognition; Information processing (psychology); Intelligence; Learning; Linguistics; Neurobiology; Psycholinguistics
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