Advances in Intelligence Testing

Alfred Binet was an unlikely contributor to the history of mental retardation, in that he neither held a degree in psychology nor was he a medical doctor. Binet earned a degree in law in 1878, but took a great interest in psychology after finishing school. He educated himself on the subject of psychology, and his fascination with hypnosis led to an interest in development and intelligence.

In 1894, Binet was given the position of Director of the Sorbonne's Laboratory of Experimental Psychology after working there for only three years. He supervised a student named Theodore Simon, who was working towards his doctorate. The two collaborated on a test that measured a child's typical abilities during different stages of development. The resulting test (the first intelligence test) came to be known as the Binet-Simon scale.

Lewis M. Terman standardized the Simon-Binet Scale using a large American sample to represent the norm. Terman was a graduate of Clark University, receiving his Ph.D. in 1905. He was interested in the study of intelligence and explored individual variations of intellectual functioning. He used a multi-test approach to make a distinction between different levels and types of intelligence. Terman happened to be employed by Stanford University. There, he worked with a team of graduate students who helped him gather information with the goal of revising the Binet-Simon scale. The final revision was published in 1916. The phrase 'intelligence quotient' first appears in this revision, measuring the ratio between mental and chronological age. The intelligence quotient (or IQ) was based on Binet's concept of "mental level."

Terman's revision of the Binet-Simon scale was renamed the Stanford-Binet. This test was the most frequently used measurement of intelligence up until the time the family of Wechsler Intelligence Scales emerged in the 1940s.

Henry Herbert Goddard was another psychologist who worked with the Binet intelligence test. He translated the Binet scale into English in 1908, and distributed the test throughout the United States. He worked as the Director of Research at Vineland Training School for Feeble-Minded Girls and Boys in the state of New Jersey. This facility was the first in the United States to establish a laboratory dedicated to the study of mental retardation. Goddard was instrumental in making the use of IQ tests an important part of the diagnosis of mental retardation.

In 1910, Goddard introduced a system of classifying individuals based on their intelligence quotient, the same measure used in Terman's revision of the Binet-Simon Scale, which was not published until 1916. Goddard used the term moron for the mildly retarded, imbecile for the severely retarded, and idiot for those who had profound mental retardation.

Goddard was a promoter of eugenics with regard to mental retardation. He was very concerned with preventing mentally retarded individuals from breeding. He thought that segregating the population of mentally retarded individuals from regular society was a workable method for achieving this goal (in place of compulsory sterilization). He apparently did think that compulsory sterilization would solve society's problem of mental retardation once and for all, however, which is in fact an untrue proposition. He understood that the idea of sterilization would not gain acceptance in U.S. society.

Although used extensively throughout the early part of the twentieth century, the Binet tests and variations (including the Stanford-Binet) are less commonly administered today. Instead, a set of intelligence tests originally developed by psychologist David Wechsler has taken their place. Primary among the Wechsler tests are the Wechsler Adult Intelligence Scale (WAIS), Wechsler Intelligence Scale for Children (WISC), and the Wechsler Preschool and Primary Scale of Intelligence (WPPSI). Wechsler is responsible for introducing the idea of an IQ score with a standardized mean of 100 and fixed standard deviation of 15. He also introduced the idea that intelligence (as measured by IQ tests) can be divided into verbal and performance/spatial components, each yielding a separate domain-specific IQ score.