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History of IQ Tests

Technically speaking, the first IQ test was developed by French psychologist, Alfred Binet in 1905. His test has provided the base for all modern IQ tests that are widely used today. However, the interest of scientists and psychologists in intelligence dates back to thousands of years.

Though a number of small studies over intelligence were carried out from time to time, it was in 1859 when concrete experiments and studies over the concept of IQ started after the publishing of Charles Darwin's "The Origin of Species". Fascinated by Darwin's theory, Sir Francis Galton, a British scientist, tried to discover the relationship between heredity and human ability.

In those times, it was believed that the human race had a small number of geniuses and idiots, while the vast majority was intelligent people. Whatever someone achieved in life depended on their hard work and will-power. Galton was not convinced. He believed that mental traits were based on physical factors. His idea on intelligence was in turn influenced by the work of a Belgian statistician named Lambert Adolphe Jacques Quetelet.

Quetelet had applied statistical methods to the study of human characteristics and had discovered the concept of normal distribution. He discovered the "tendency for the bulk population to fall somewhere between the two extremes, with numbers dropping sharply at either extreme. If plotted on a chart, these values assumed a shape roughly like that of a bell."

Galton published his ideas on "hereditary intelligence" in his book Hereditary Genius. This was the first scientific investigation into the concept of intelligence. In the 1890s, James McKeen Cattell, an American student of Galton, brought the idea of intelligence testing to America. The test was popular for a brief period but failed to hold on to its popularity as scoring well on this test was never an indicator of a student doing well in his academics.

It was then that Alfred Binet came into picture. Binet was passionate about testing and measuring human capabilities. He tried to understand 'intelligence' through intense trial-and-error testing methods. He worked with two groups of students - average & mentally handicapped. Binet discovered that there were certain tasks that average students could handle but the handicapped students could not. Binet then calculated the normal abilities for students at each age and pinpointed how many years a student's mental age was above or below the normal.

The Paris educational authorities came across Binet's work and were largely impressed by it. In 1904, the French government commissioned him to find a method by which they could differentiate between intellectually normal and inferior children. Binet conducted the test on Paris school children and created a standard based on his data. For example, if 80 percent of 9-year-olds could pass a particular test, then success on the test represented the intelligence level of a 9-year-old.

This led to the development of the Binet Scale, also known as the Simon-Binet Scale in recognition of Theophile Simon who assisted Binet in his work. They devised a formula and calculated the IQ based upon their formula:

IQ = Mental Age/Chronological Age X 100

This Simon-Binet test proved to be highly effective in categorizing the children into various groups based upon their IQ scores. Thus, we can say that the IQ test was finally born in 1905!

However, the history of IQ test doesn't end here as the term IQ or "intelligence quotient" was not born yet. We had just got the test but not the name.

The idea that a test could actually determine a child's "mental age" became enormously popular and eminent scientists and psychologists started studying it. In 1912, a German psychologist Wilhelm Stern noticed an interesting thing. He observed that even though the gap between mental age and chronological age widened as a child mature, the ratio between them remained constant. Therefore, a 10-year-old scoring like an 11-year-old (110) would not be as intelligent as a 5-year-old scoring like a 6-year-old (120).

In Stern's Binet test scoring system, an average IQ score was 100. Any score above 100 was above average, while any score below 100 was below average. American psychologist Lewis Terman revised this test into a more compatible one suited for people of all age groups. Terman changed the concept of a mental age in Stern's Binet test scoring system into a standardized IQ score. He was the first person to coin the term intelligence quotient. Thus, the term IQ was also born.

Terman's first standardized test was published in 1916 and was called as the Stanford-Binet Intelligence Scale. It was enthusiastically accepted in America and in that same year, it was administered to a prisoner on trial for murder. The prisoner fared so poorly in the test that the Wyoming jury acquitted him on grounds of poor mental condition.

The greatest spurt in the usage IQ tests came in 1917 when America entered World War I. The U.S. Army, faced with the dilemma of sorting huge numbers of draftees into various Army positions, made a committee of seven leading psychologists including Terman to devise a mass intelligence test. Terman had a student named Arthur Otis who had already developed a 'group testing' method. His materials were adopted by the committee and a trial run was conducted on 4,00O men. By the beginning of 1919, nearly two million American men had taken the Army intelligence tests.

Thereafter, many companies adopted testing programs and intelligence tests came into wide practice. The post World War I era witnessed IQ tests being a part of the schooling system in the country. The concept of intelligence continued to evolve and in 1983, a psychologist Howard Gardner made another breakthrough in the field of IQ tests. Gardner defined seven distinct intelligences and his concept of multiple intelligences broadened the idea of "intelligence" from a mathematical and verbal understanding.

To sum up, I can just say that the history of IQ testing continues to the modern day.