David Wechsler

Wechsler studied at the City College of New York and Columbia University, where he obtained his MA in 1917, Ph.D. in 1925 under Robert S. Woodworth. He was psychologist to Camp Logan of US Army, Texas in 1917, and was sent by the army to University of London where he worked with the psychologist Charles Spearman (1863-1945) and the mathematician Karl Pearson (1857-1936).He subsequently began a long lasting affiliation with the Bellevue Psychiatric Hospital in New York where he was chief psychologist from 1932 to 1967. During the years 1922 to 1925 he was clinical psychologist at Bureau of Child Guidance, New York. He was acting secretary to the Psychological Corporation 1925 to 1927, and had private practice as a clinical psychologist (1927-1932). From 1933 to 1967 he was clinical professor, Medical College, New York University.

Work
During World War I, Wechsler was assigned to assist Edwin Garrigues Boring (1886-1968) in testing army recruits. His observations on the inadequacies of the Army Alpha Tests brought him to the conclusion that academically defined "intelligence" was in no way applicable to "real life" situations. These tests are designed to measure abilities of conscripts from wildly differing backgrounds and assign them to military jobs best suited to their abilities.

He realized that an adequate definition of intelligence must be broader and have validity. Wechsler considered Spearman's two-factor theory of 'g' and many s's to be simplistic. He understood intelligence to be more of an effect, rather than a cause.

In 1938 Wechsler developed a ”battery” of intelligence tests known as the Wechsler-Bellevue Intelligence Scale. The original battery was specially aimed at the measurement of the intelligence of adults for clinical purposes. He denied the idea that there is a mental age against which the capacity of man can be measured, and he defined intelligence as the aggregate, or global capacity to act purposefully, to think rationally, and to deal effectively with his environment which included the idea that intelligence is not a single capacity but a multifaceted aggregate. To Wechsler, normal intelligence is the average test score for members of a defined group. The number 100 on a standard scale should then represent the average.

The Wechsler-Bellevue test soon became the most widely used intelligence test in the USA. He revised the test in 1942, and published the Wechsler Intelligence Scale for Children in 1949. This was updated in 1974. In 1955 he developed another intelligence test for adults, the Wechsler Adult Intelligence Scale (WAIS), with the same structure as his previous scale, but standardised against different population groups, including 10 non-white, to mirror the population as a whole. The former test had been standardised for an all white population. WAIS was revised in 1981, shortly before Wechsler’s death. Wechsler’s last intelligence test, Wechsler Preschool and Primary Scale of Intelligence, was published in 1967 as an adaptation of the children’s scale intended for very young children.

• The Range of Human Capacities. 1935.
• The Measurement of Adult Intelligence. 1939.
• WISC. 1949.
• WAIS. 1955.
• The Measurement and Appraisal of Adult Intelligence. 1958.
• C. Spearman:
  General Intelligence, Objectively Determined and Measured. 1904.