Intelligence tests have a history stretching back to the early 20th century, deeply intertwined with the history of psychology, education, immigration policy, and eugenics. Understanding this history is essential for interpreting what IQ tests measure — and what they miss.
Alfred Binet, a French psychologist, created the first practical intelligence test in 1905, commissioned by the French government to identify children who needed special educational assistance. Binet himself warned explicitly that his test measured current performance, not fixed or innate intelligence.
American psychologist Henry Goddard translated Binet's test into English and used it to test immigrants at Ellis Island — controversially concluding that large percentages of Jewish, Hungarian, Italian, and Russian immigrants were 'feebleminded.' These results were used to support restrictive immigration laws in the 1920s.
Lewis Terman at Stanford revised the test as the Stanford-Binet IQ test in 1916, introducing the concept of Intelligence Quotient (IQ) as mental age divided by chronological age, multiplied by 100. The test was used extensively to assign military roles in World War I.
Modern IQ testing has been refined considerably, but debates continue about what intelligence tests measure, whether intelligence is a single trait or multiple, and whether tests are culturally biased. The Flynn Effect — the documented rise in average IQ scores across the 20th century — challenges simple genetic interpretations.
Frequently Asked Questions
Who invented the IQ test?
Alfred Binet created the first practical intelligence test in 1905 in France. The concept of the IQ score was formalized by Lewis Terman at Stanford in 1916 with the Stanford-Binet test.
What does IQ actually measure?
IQ tests measure performance on specific cognitive tasks including pattern recognition, verbal reasoning, working memory, and processing speed. They correlate with academic achievement and some life outcomes, but they capture only part of what we intuitively mean by 'intelligence.'
