dyslexia (dĬslĕk´sēə), 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.