- David Wechsler (1896–1981) was an American psychologist who worked at Bellevue Hospital in New York.
- Earlier tests divided mental age by actual age to get an IQ ratio, which broke down for adults whose abilities plateau.
- The Wechsler Adult Intelligence Scale (WAIS) and the Wechsler Intelligence Scale for Children (WISC) are the modern descendants of his work.
- He measured several distinct abilities, such as verbal comprehension and perceptual reasoning, rather than reporting a single number alone.
Who was David Wechsler?
David Wechsler (1896–1981) was an American psychologist who worked at Bellevue Hospital in New York. Dissatisfied with existing tests built for children, he designed a battery suited to adults. His Wechsler-Bellevue scale of 1939 grew into the most widely used intelligence tests in the world.
What is the deviation IQ?
Earlier tests divided mental age by actual age to get an IQ ratio, which broke down for adults whose abilities plateau. Wechsler replaced this with the deviation IQ, scoring each person against the average for their own age group. By definition the average is set to 100, with a standard spread, so a score shows how far someone falls above or below typical performance.
What are the WAIS and WISC?
The Wechsler Adult Intelligence Scale (WAIS) and the Wechsler Intelligence Scale for Children (WISC) are the modern descendants of his work. Both are periodically revised and restandardized to stay current. They are administered one-on-one by trained professionals and remain clinical standards worldwide.
Why did Wechsler's approach win out?
He measured several distinct abilities, such as verbal comprehension and perceptual reasoning, rather than reporting a single number alone. This profile gave clinicians richer, more practical information. The deviation IQ also made scores comparable across ages, which is why nearly all modern tests now use it.