IQ (Intelligence Quotient) is one of those topics that can keep conversation at a dinner party lively for hours. Everyone likes to speculate what the IQ of this and that famous person is, or a mutual friend, or even self. All have an opinion on the validity of IQ scores - but few people know the history of IQ tests.
Mankind has always been interested in the concept of intelligence, but serious research into it really only dates back to the nineteenth century when the British scientist, Sir Francis Galton, began looking into the relationship between heredity and human abilities. His work was later utilized by a Belgian statistician, Lambert Adolphe Jacques Quetelet. He was probably the first person to scientifically employ statistical methods in studying human characteristics. Part of his discovery from this work was the idea of normal distribution, which has an important role to play in IQ tests.
Many were now of the belief that intelligence could be measured, and this view arrived in the US, towards the end of the nineteenth century, brought by an American student of Galton, James McKeen Cattell.
Despite all the interest in measuring Man's intelligence, no one came up with a universally accepted way of so doing. Then in 1904, the French government asked renowned psychologist Alfred Binet to find a way to pick out those children who would struggle at school, with the intention of setting up special schools for them.
Binet and a colleague, Theodore Simon, began the task, and took into consideration a range of attributes that help children succeed with their education, such as attention, memory and problem-solving skills. Tests were devised which would measure these, and Paris children, in 1905, were asked to follow commands, copy patterns, name objects and also to put things in the correct order. Thus was the first IQ test devised. The data was used to define standards and norms. This first intelligence test became known as the Binet-Simon Scale.
The test aroused much interest around the world, including in the US. Here, Lewis Therman, a psychologist at Stanford University, used the Binet-Simon Scale on a sample of Americans and adapted the test to suit the US. This test became the standard test used in America, and is known as the Stanford-Binet Intelligence Scale and was first used in 1916. It is this scale that uses a single number, the IQ, to represent the score achieved in the test.
The next step in the development of tests to measure intelligence occurred when the military in the US needed to screen huge numbers of recruits quickly. Robert Yerkes developed two tests, the Army Alpha and Beta tests - the former written, the latter oral - to assist in assessing the best personnel for particular roles, such as leadership. The tests were introduced in 1917, and remained in use for many years after-wards, in a variety of scenarios outside the armed forces.
The last leg in the history of IQ tests lies with David Wechsler who introduced his Wechsler Adult Intelligence Scale (WAIS) in 1955, now on version WAIS-III. The key difference from Binet is Wchsler scores by comparing the test score to others in the same age group - Binet based his tests on chronological age. Doubtless IQ tests will see further revisions in the future.
