The Binet-Simon Scale, the first test of intelligence, was developed in France by Alfred Binet and Theodore Simon for testing children. Originally issued in 1908, it consisted of 30 tests arranged in order of increasing difficulty. From the average scores of children, Binet developed the concept of mental age.

The best-known Binet adaptation, created by Stanford University’s L. M. Terman in 1916, is the Stanford-Binet Intelligence Scale. Terman introduced the term intelligence quotient (IQ), which is a numerical value given to scores on an intelligence test (a score of 100 corresponds to average intelligence).

The Stanford-Binet is designed to measure skills in four areas: verbal reasoning, abstract/visual reasoning, quantitative reasoning, and short-term memory.

The Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) was developed by David Wechsler especially for adults. The test measures both verbal and performance abilities. Wechsler also created the Wechsler Intelligence Scale for Children-Third Edition (WISC-III), which is meant to be used with school-aged children. It measures verbal and performance abilities separately, though it also yields an overall IQ score.

Group tests aim to overcome the problems of time and expense associated with individual tests and to eliminate bias on the part of the examiner. However, in a group setting the examiner is less likely to notice whether an individual test taker is tired, ill, or confused by the directions. Emotionally disturbed children and people who have less experience taking tests usually do better on individual tests than on group tests.

Some intelligence tests may discriminate against members of certain cultural or ethnic groups. Performance tests are intelligence tests that do not involve language, so they can be useful for testing people who lack a strong command of English. The Seguin Form Board, the Porteus Maze, and the Bayley Scale of Infant Development are performance tests.

Culture-fair tests are designed to eliminate cultural bias by minimizing skills and values that vary from one culture to another. The Goodenough-Harris Drawing Test and the Progressive Matrices are examples of culture-fair tests.