dyslexia, in psychology, a developmental disability in reading or spelling, generally becoming evident in early schooling. To a dyslexic, letters and words may appear reversed, e.g., d seen as b or was seen as saw. Many dyslexics never learn to read or write effectively, although they tend to show above average intelligence in other areas. With the aid of computerized brain scans such as positron emission tomography (PET), recent studies have offered strong evidence that dyslexia is located in the brain. Damage to the brain can cause a reading disability similar to dyslexia, known as acquired dyslexia or alexia.

Chronic neurological disorder causing inability or great difficulty in learning to read or spell, despite normal intelligence. It inhibits recognition and processing of graphic symbols, particularly those pertaining to language. Symptoms, including very poor reading skills, reversed word and letter sequences, and illegible handwriting, usually become evident in the early school years. With early recognition and specialized approaches to teaching reading, most dyslexics can learn to read. Anomalies have recently been found in reading-related pathways in the brains of dyslexic persons.

Learn more about dyslexia with a free trial on Britannica.com.