History of IQ Testing

Modern intelligence testing developed over more than a century. The meaning of “IQ” changed along the way: early tests focused on identifying children who needed educational support, age-ratio formulas later popularized the term intelligence quotient, and modern clinical tests use standardized norms and multiple cognitive tasks.

1905: Binet and Simon

Alfred Binet and Théodore Simon published an early practical intelligence scale in France. Their goal was to identify children who might need additional help in school. The tasks sampled abilities such as comprehension, judgment, reasoning, memory and attention.

William Stern and the IQ concept

William Stern proposed an intelligence quotient based on the relationship between mental age and chronological age. The term “IQ” survived even after professional scoring methods moved away from the simple age-ratio formula.

Stanford–Binet

The Binet–Simon tradition was adapted and standardized in the United States, becoming the influential Stanford–Binet family of intelligence scales.

David Wechsler and the WAIS

David Wechsler developed a different family of intelligence scales. Modern versions use multiple subtests and index scores. The current U.S. adult edition, WAIS-5, was published in 2024.

Online tests are different. FreeIQTest.info is an informal IQ-style reasoning quiz. It is not a clinical assessment and is not affiliated with or equivalent to the WAIS, Stanford–Binet or another professionally standardized test.