In 1905, Alfred Binet was asked, by the French government, to create a test destined to measure
children’s intelligence in the hope of evaluating their cognitive disabilities. Its purpose was to
avoid sending those youngsters to an asylum by establishing if they were merely slow as
opposed to insane: The Binet-Simon test2.
A few years later, in 1912, a German psychologist named William Stern4 invented the term
Intelligence Quotient3 or I.Q. in short. It represented the ratio between a child’s mental age and
his or her real age for comparison purposes.
Then, in 1916, Alfred Binet inspired Lewis Terman, a psychologist from the Stanford Graduate
School of Education, to create the first intelligence scale along with his Stanford-Binet11 test.
In 1939 the calculating method was changed, namely by David Wechsler5, an American
psychologist, to a relative score15 comparing itself to other test-taker’s score, of the same age
group, in the same country. He thought intelligence was constituted of several elements which
could be measured by several large subtests representing a particular aspect of cognitive ability6.
His tests, each aimed at one age group, are still the most famous and widely used ones in the
world (WPPSI, WISC, and WAIS243).
To him, intelligence was the faculty to be logical, reach one’s goals, and be in control of one’s
life outcomes.7
Wechsler’s tests, in the USA, rival with James McKeen Cattell’s8 who was the first American
psychology professor, and author for the Science Journal. He eventually designed his own test,
based on a wider scale than Wechsler’s.