What is IQ?

French psychologists Alfred Binet and Théodore Simon created the first practical intelligence test in 1905 to identify children who needed extra help at school. German psychologist William Stern introduced the term intelligence quotient in 1912. Modern tests are scaled so the population average is 100 with a standard deviation of 15, meaning about 68 percent of people score between 85 and 115 and only about 2 percent score above 130. Average raw scores rose by roughly three points per decade through the 20th century, a trend known as the Flynn effect. IQ predicts some outcomes like school performance, but it does not measure creativity, emotional intelligence or every kind of talent.