Alfred Binet, a French psychologist, collaborated with Théodore Simon to develop the first practical intelligence test in 1905, known as the Binet-Simon scale. This test, commissioned by the French government, assessed cognitive abilities like memory and problem-solving, and introduced the concept of “mental age” to gauge intellectual development compared to typical age norms.

Binet believed that intelligence was multifaceted and influenced by various factors, cautioning against using his test as a definitive measure of intelligence. His intent was to use the scale for educational guidance rather than as an absolute assessment.

After Binet’s death, his work was further developed in the U.S. by psychologist Lewis Terman, who created the Stanford-Binet Intelligence Scales. Terman’s version refined the calculation of Intelligence Quotient (IQ) and popularized IQ tests, establishing them as a standard tool in educational and psychological evaluations.