IQ testing has become a global shorthand for measuring intelligence, but few people know where it came from, how it evolved, or why it became so widely used. From classrooms to military recruitment to job screening, IQ tests have had a major influence on society — for better and worse. Here’s a brief look at the surprising history behind the concept of “intelligence quotient.”
The Origins: France in the Early 1900s
The first modern IQ test was created in 1905 by Alfred Binet and Théodore Simon, two French psychologists. The French government wanted a way to identify schoolchildren who needed extra help. Binet’s test focused on practical, age-appropriate tasks — not abstract ideas of genius. His goal wasn’t to label kids, but to help them learn more effectively.
Interestingly, Binet warned against using the test to permanently rank children. He believed intelligence was flexible and could develop over time — a view often ignored in later years.
The Birth of the IQ Score
In 1912, German psychologist William Stern introduced the idea of a “quotient.” He proposed measuring a child’s “mental age” and dividing it by their actual age. The formula looked like this:
IQ = (Mental Age ÷ Chronological Age) × 100
So if a 10-year-old performed like a 12-year-old, their IQ would be 120. This formula worked reasonably well for children but fell apart for adults, where mental development levels off.
The U.S. Military and Mass Testing
During World War I, psychologist Lewis Terman (at Stanford University) adapted Binet’s work and created the Stanford-Binet Intelligence Scale — one of the first versions used widely in the U.S. The military used it to sort recruits into roles. This was the first time IQ testing was done at scale, and it helped cement the idea that intelligence could be measured with a single number.
Unfortunately, this era also saw the rise of eugenics, and IQ testing was weaponized to support biased ideas about race, immigration, and social class. Low scores were often misunderstood or misused to deny rights or opportunities.
From Academia to Everyday Use
Throughout the 20th century, IQ testing evolved into more sophisticated tools like the Wechsler Adult Intelligence Scale (WAIS) and the Raven’s Progressive Matrices, which removed verbal and cultural bias as much as possible. These tests began to assess more aspects of intelligence, such as working memory, processing speed, and abstract reasoning.
Schools began using IQ tests to place students in gifted programs or special education. Employers, psychologists, and even governments sometimes used them in hiring or policy decisions.
Controversy and Criticism
IQ testing has never been without debate. Critics argue that it:
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Overemphasizes a narrow definition of intelligence
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Reinforces social and cultural bias
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Fails to account for creativity, emotional intelligence, or motivation
Supporters counter that, when used properly, IQ tests can predict academic performance and certain job-related skills — but they agree that misuse is a serious problem.
Where We Are Now
Today, IQ tests are still used, but with more caution and context. Modern psychologists stress that intelligence is multifaceted, and a single number can’t capture everything about a person’s abilities or potential.
Online IQ tests have exploded in popularity, but most are unofficial and unreliable compared to clinically administered tests.