Intelligence quotient

Lore & Background

He hypothesized a correlation between intelligence and physical traits such as reflexes and head size, but was unable to show any such correlation and abandoned this research. French psychologist Alfred Binet and psychiatrist Théodore Simon had more success in 1905, publishing the Binet–Simon Intelligence test, which focused on verbal abilities and was intended to identify 'mental retardation' in school children. The score on their scale revealed a child's mental age.

Reader's Guide

The concept of IQ has had significant impact on education, military selection, and employment. During World War I, the U.S. Army used mental tests developed by Robert Yerkes, Terman, and Goddard to evaluate and assign recruits, leading to the first mass-produced written tests of intelligence. These tests generated controversy and public debate, and their results are considered dubious and controversial, having rested on contested assumptions about heritability and innate intelligence. Historically, many proponents of IQ testing have been eugenicists who used pseudoscience to push ideas of racial hierarchy, but such ideas have been rejected by a strong consensus of mainstream science. The heritability of IQ has been studied for nearly a century, with ongoing debate over the significance of heritability estimates and mechanisms of inheritance. The Flynn effect shows that raw scores on IQ tests have been rising at an average rate of three IQ points per decade since the early 20th century.

Did You Know?

• The Binet–Simon Intelligence test was intended to identify 'mental retardation' in school children, in contradistinction to claims that these children were 'sick' and should be removed to asylums.
• Raw scores on IQ tests have been rising at an average rate of three IQ points per decade since the early 20th century, a phenomenon called the Flynn effect.