History of IQ Tests

Dr. Russell T. Warne

Sep 8, 2023

In the 19th century, several scientists worked on the problem of trying to measure intelligence. The most well known attempt was by Sir Francis Galton (1822-1911). In the 1880s, he set up a laboratory in London and took measurements of physical and sensory traits, including head circumference, reaction time, visual acuity, and grip strength. Galton believed that these variables would relate to social class, which he thought was a manifestation of intelligence. After years of collecting data, he found no relationship between the traits he measured and social class. With 21st century hindsight, we now know that some of those variables really have no relationship with intelligence (e.g., grip strength) and others do (e.g., reaction time), but that Galton’s methods were not sensitive enough to detect the relationship. It was still a noteworthy attempt.

Alfred Binet and the First Successful Intelligence Test

The first successful intelligence test was published by Alfred Binet and Theodore Simon in Paris in 1905. Binet had been conducting psychological research on cognitive development for years, and he was interested in intelligence and education. At the time, French society was having a debate about how to educate children with special needs. Binet and Simon created their test as part of their advocacy for special education classes to be housed in schools and not psychiatric facilities. An improved test was published in 1908 and a revision in 1911.

Lewis Terman and the Stanford-Binet

Binet and Simon’s intelligence test was very popular and was quickly translated into other languages, including German, Italian, and English. Americans embraced the tests and used them to evaluate children who were suspected of having special needs. Stanford University psychologist Lewis Terman went further. He expanded Binet and Simon’s test to cover a wider range of intelligence and examinee ages. Terman called the new test the Stanford-Binet and published it in 1916.

Army Alpha and Army Beta IQ tests

Shortly after the Stanford-Binet was published, Terman joined a committee chaired by the president of the American Psychological Association, Robert Yerkes. This committee had the goal of working with the United States Army to assist the military’s efforts in World War I. These psychologists created intelligence tests that could be used to identify men who would be good candidates for leadership positions (if they scored well on the test) or who would be best to release from military service (for scoring poorly). All intelligence tests until that point had been individually administered. But with the large number of men drafted into the army, individual testing was impractical. The committee’s solution was two tests that could be administered to large groups of people: the Army Alpha (for literate examinees) and the Army Beta (for men with low or no literacy).

The Army Alpha and Army Beta were wildly successful. Over 2 million tests were administered before the war ended. The tests were found to predict training success, correlate with military rank, and correlate with pre-war job prestige and education levels. Although the tests had no impact on the outcome of World War I, the Army Alpha and Army Beta proved that mass testing was possible and that IQ scores had relevance for adults outside of the schoolhouse.

Later IQ Tests

More innovations to IQ happened throughout the 20th century. David Wechsler created his series of Wechsler IQ tests from 1939 until his death in 1981, and modern versions of these tests are the most popular intelligence tests today. Wechsler introduced the deviation IQ score and a nonverbal IQ and a verbal IQ to provide nuance that is lost with an overall IQ score. Georg Rasch introduced a new scoring system called “item response theory” that improved many aspects of test items and scoring.

Computer-Administered IQ Tests

In the late 20th century, Q test creators were some of the first psychologists to realize the importance of personal computers. Computer-administered tests started appearing in the early 1980s, and by the turn of the millennium, they were common in education. The COVID-19 pandemic added demand for administering IQ tests via computers, and many traditional tests have adapted to teletherapy and telehealth settings.

The Reasoning and Intelligence Online Test (RIOT) is another major milestone in the history of IQ tests. The RIOT is the world’s first online IQ test that is designed to meet all of the relevant ethical and technical standards for psychological tests established by the American Educational Research Association, American Psychological Association, and the National Council on Measurement in Education. Its innovations are valuable, but would not have been possible without the breakthroughs and innovations of earlier scientists.

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