American psychologist and inventor of several widely used intelligence tests (intelligence test) for adults and children.

Wechsler studied at the City College of New York and Columbia University, receiving his doctorate in 1925. He began a long association with Bellevue Psychiatric Hospital in New York City, serving as chief psychologist from 1932 to 1967. In 1939 he produced a battery of intelligence tests known as the Wechsler-Bellevue Intelligence Scale. The original battery was geared specifically to the measurement of adult intelligence, for clinical use. He rejected the idea that there is an ideal mental age against which individual performance can be measured, and he defined normal intelligence as the mean test score for all members of an age group; the mean could then be represented by 100 on a standard scale. The Wechsler-Bellevue test quickly became the most widely used adult intelligence test in the United States, and in 1942 Wechsler issued his first revision. The Wechsler Intelligence Scale for Children was published in 1949 and updated in 1974. In 1955 Wechsler developed yet another adult intelligence test, the Wechsler Adult Intelligence Scale (WAIS), with the same structure as his earlier scale but standardized with a different population, including 10 percent nonwhites to reflect the U.S. population. (The earlier test had been standardized for an all-white population.) He contributed to the revision of the WAIS in 1981, shortly before his death. The last of his intelligence tests, the Wechsler Preschool and Primary Scale of Intelligence, was issued in 1967 as an adaptation of the children's scale for use with very young children. His intelligence tests continue to be updated for contemporary use.