History of IQ Tests

Intelligence tests feel like a modern invention, but the idea of measuring mental ability has roots going back more than a century. IQ tests grew out of a mix of scientific curiosity, educational needs, and, at times, controversial social policies.

Early Beginnings

In the late 19th century, psychologists began wondering how to measure differences in mental ability. Early efforts by researchers like Francis Galton focused on basic sensory tasks (reaction time, eyesight, etc.), assuming sharper senses meant higher intelligence. These attempts didn’t really work, but they set the stage for more serious tools.

Binet and the First Practical IQ Test

The first truly practical intelligence test was created in the early 1900s by French psychologist Alfred Binet. The French government wanted a way to identify children who needed extra help in school. Binet designed tasks involving memory, vocabulary, and problem solving, and introduced the idea of “mental age” — how a child’s performance compared to average children of the same age.

Later, German psychologist William Stern coined the term “IQ” (intelligence quotient), originally calculated as (mental age ÷ chronological age) × 100.

Mass Testing and the 20th Century

During World War I, the U.S. Army used group intelligence tests (the Army Alpha and Beta) to help classify soldiers. After the war, IQ testing spread quickly into schools, workplaces, and research. Tests like the Stanford–Binet and Wechsler scales became standard tools for psychologists.

At the same time, IQ tests were misused to justify racist and classist policies, including immigration limits and forced sterilization. This dark history is a major reason why modern psychologists emphasize careful, ethical use of testing.

Modern IQ Testing and Ongoing Debates

Today’s IQ tests are more sophisticated, measuring different aspects of thinking: verbal skills, working memory, processing speed, and visual–spatial reasoning. They are standardized on large, diverse samples and updated regularly to account for changing population averages.

Still, IQ tests are debated. Supporters see them as useful tools for identifying learning needs, researching cognition, and selecting for certain roles. Critics argue they can reflect cultural bias, miss important forms of intelligence (like creativity or social skills), and be misinterpreted as fixed “scores on a person’s worth.”

In short, IQ tests have evolved from crude experiments into powerful but imperfect tools. They can tell us something real about certain mental abilities — but never the whole story of a person’s potential.