Dyslexia: Evolution of a concept

Abstract

It was recognized at a relatively early stage of medical history that injury or disease of the brain in adult patients could cause a loss of a specific cognitive skill such as the ability to name objects or the ability to read. Indeed observations of this type were often employed as an argument in favor of localization of function in the brain. Thus specific anomia or "loss of memory for words" was clearly described in the 16th century and the syndrome of alexia without agraphia was identified in the 17th century. But neither physicians nor educators were as quick to recognize that children might also suffer from specific cognitive disabilities as a consequence of congenital or early acquired disease. It was only in 1853 that the Dublin otologist, William Wilde, published his observations on children who were "dumb, but not deaf," i.e., suffering from specific language disability. As we know, developmental dyslexia went unrecognized until the end of the 19th century when Morgan published his famous case report. As so often happens, once the attention of physicians was called to the condition, they immediately observed it in their practice and a steady stream of papers on dyslexia appeared in the English and German medical literature between 1900 and 1910. Somewhat later, clinical psychologists recognized dyslexia as a distinctive condition and attempted to relate its occurrence to more basic defects in visualization, auditory perception and associational processes. On the other hand, educators were less ready to accept the real existence of "congenital wordblindness" as a clinical entity.