The psychometric approach to intelligence emphasizes people’s performance on standardized aptitude tests. Aptitude tests predict people’s future ability to acquire skills or knowledge. Achievement tests, on the other hand, measure skills and knowledge that people have already learned.
Intelligence tests can be given individually or to groups of people. The best-known individual intelligence tests are the Binet-Simon scale, the Stanford-Binet Intelligence Scale, and the Wechsler Adult Intelligence Scale.
Alfred Binet and his colleague Theodore Simon devised this general test of mental ability in 1905, and it was revised in 1908 and 1911. The test yielded scores in terms of mental age. Mental age is the chronological age that typically corresponds to a particular level of performance.
Example: A ten-year-old child whose score indicates a mental age of twelve performed like a typical twelve-year-old.
In 1916, Lewis Terman and his colleagues at Stanford University created the Stanford-Binet Intelligence Scale by expanding and revising the Binet-Simon scale. The Stanford-Binet yielded scores in terms of intelligence quotients. The intelligence quotient (IQ) is the mental age divided by the chronological age and multiplied by 100. IQ scores allowed children of different ages to be compared.
Example: A ten-year-old whose performance resembles that of a typical twelve-year-old has an IQ of 120 (12 divided by 10 times 100).