Definition

Dyslexia is an unexpected impairment in reading and spelling despite a normal intellect.

Description

Dyslexia was first described by Hinshelwood in 1896. Orton originally hypothesized that dyslexia results from a dysfunction in visual memory and visual perception due to a delayment in maturation. Most dyslexics also display poor writing ability. Dyslexia is a classical primary reading disorder and should be differentiated from secondary disorders such as mental retardation, educational or environmental deprivation, or physical/organic diseases. The disorder results as a combination of genetic and environmental causes, which can induce variations in the behavioral, cognitive, and physiological measures related to reading disability. Dyslexia was previously called congenital word blindness. Dyslexia is a reading...