IQ, or intelligence quotient, is a measure of intelligence that schools, children's homes, and other child-saving institutions have used since the 1910s to assess the intelligence of children for various diagnostic purposes. Welcomed and reviled in different social and political contexts in the twentieth century, especially in the United States, because its deployment has influenced the life chances of millions of children, the IQ and the tests that produce it had modest beginnings. French psychologist ALFRED BINET devised the first test of intelligence for school children in 1908 and 1911. He understood that intellectual capacity increased as children matured; his age scale, which he obtained as a norm of right over wrong answers about everyday artifacts and information for each year of childhood, was based on the Gaussian bell-shaped curve. The result gave the child's "mental age." If the child was three years old and her or his mental age was normal for a three year old, then the child was normal because his or her chronological and mental ages were the same. If the child's mental age was "higher" than her or his chronological age, then the child was advanced, or had a higher than normal IQ. If the situation were reversed, then the child was behind or retarded, with a lower than normal IQ for his or her age. There were several tests for each age, and Binet expressed scores as mental ages. His great insight was that mental age existed apart from, but was related to, chronological age. William Stern, of Hamburg University, devised the notion of the intelligence quotient–soon dubbed the IQ – by dividing the child's mental age by her or his chronological age. Thus a child of ten with a mental age of twelve would have an IQ of 120. One with a chronological age of five and a mental age of four would have an IQ of only 80, and so on.
The American psychologist Lewis M. Terman, of Stanford University, "Americanized" the Binet test, and Stern's notion of the IQ, in the 1910s. He standardized the Binet test on many small town, middle-class California school children of northwestern European, Protestant extraction, so that the norms for each age were synchronized with cultural knowledge best understood by such children–and their relatives, peers, and neighbors. In transforming Binet's test into the Stanford-Binet measuring scale of intelligence, or, more simply, the Stanford-Binet, Terman insisted that the test measured innate intelligence in individuals and in groups, and this assumption was not widely or seriously questioned by mainstream academic psychologists until the 1960s. The Stanford-Binet became the model for subsequent IQ tests and tests of intelligence, in the United States for the next generation, thus influencing the lives of many children in America and abroad. From the 1920s to the 1960s, the IQ reigned supreme in education and social welfare institutions. Although it is true that in the 1920s there was a furious, if short-lived, controversy among social scientists over whether such tests constituted legitimate scientific measures of the "average IQ" of specific ethnic and racial groups in the population, only an ignored handful of researchers questioned whether an individual's IQ was innate at birth and stable thereafter.
After the 1960s, various constituencies and interest groups raised critical questions about IQ testing. Champions of civil rights and feminism claimed that defenders of segregation and institutionalized racism had used so-called average racial IQ scores to keep minorities and females from good schools, jobs, and neighborhoods. Some psychologists claimed that intelligence was too complex a phenomenon to be reduced to a simple ratio; most post–World War II tests, based on a model developed by the psychologist David Wechsler, argued that intelligence was the consequence of multiple factors and processes. Researchers in early childhood education insisted in the 1960s that IQs of preschool age children could and did respond to environmental stimuli and pressures by at least as much as the gap between many racial minorities and the white majority. As in the 1920s, a nature versus nurture debate took place over the next several decades without a definite conclusion. After World War II, most institutions, such as schools and child-saving organizations, tended to interpret IQ scores as mere indicators, to be used with many other indices to understand a child and her or his potentiality.
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