Home > Encyclopedia of Psychology > Intelligence Quotient

A measurement of intelligence based on standardized test scores.

Although intelligence quotient (IQ) tests are still widely used in the United States, there has been increasing doubt voiced about their ability to measure the mental capacities that determine success in life. IQ testing has also been criticized for being biased with regard to race and gender. In modern times, the first scientist to test mental ability was Alfred Binet, a French psychologist who devised an intelligence test for children in 1905, based on the idea that intelligence could be expressed in terms of age. Binet created the concept of "mental age," according to which the test performance of a child of average intelligence would match his or her age, while a gifted child's performance would be on par with that of an older child, and a slow learner's...