From Wikipedia, the free encyclopedia - View original article
An example of one kind of IQ test item, modeled after items in the Raven's Progressive Matrices test.
An example of one kind of IQ test item, modeled after items in the Raven
From Wikipedia, the free encyclopedia - View original article
An example of one kind of IQ test item, modeled after items in the Raven's Progressive Matrices test.
An example of one kind of IQ test item, modeled after items in the Raven's Progressive Matrices test.
|Abilities, traits and constructs|
|Models and theories|
|Fields of study|
An intelligence quotient, or IQ, is a score derived from one of several standardized tests designed to assess intelligence. The abbreviation "IQ" comes from the German term Intelligenz-Quotient, originally coined by psychologist William Stern. When modern IQ tests are devised, the mean (average) score within an age group is set to 100 and the standard deviation (SD) almost always to 15, although this was not always so historically. Thus, the intention is that approximately 95% of the population scores within two SDs of the mean, i.e. has an IQ between 70 and 130.
IQ scores have been shown to be associated with such factors as morbidity and mortality, parental social status, and, to a substantial degree, biological parental IQ. While the heritability of IQ has been investigated for nearly a century, there is still debate about the significance of heritability estimates and the mechanisms of inheritance.
IQ scores are used as predictors of educational achievement, special needs, job performance and income. They are also used to study IQ distributions in populations and the correlations between IQ and other variables. The average IQ scores for many populations have been rising at an average rate of three points per decade since the early 20th century, a phenomenon called the Flynn effect. It is disputed whether these changes in scores reflect real changes in intellectual abilities.
The first large-scale mental test may have been the imperial examination system in China. Modern mental testing began in France in the 19th century. It contributed to separating mental retardation from mental illness and reducing the neglect, torture, and ridicule heaped on both groups.
Englishman Francis Galton coined the terms psychometrics and eugenics, and developed a method for measuring intelligence based on nonverbal sensory-motor tests. It was initially popular, but was abandoned after the discovery that it had no relationship to outcomes such as college grades.
French psychologist Alfred Binet, together with psychologists Victor Henri and Théodore Simon, after about 15 years of development, published the Binet-Simon test in 1905, which focused on verbal abilities. It was intended to identify mental retardation in school children. The score on the Binet-Simon scale would reveal the child's mental age. For example, a six-year-old child who passed all the tasks usually passed by six-year-olds—but nothing beyond—would have a mental age that exactly matched his chronological age, 6.0. (Fancher, 1985). In Binet's view, there were limitations with the scale and he stressed what he saw as the remarkable diversity of intelligence and the subsequent need to study it using qualitative, as opposed to quantitative, measures (White, 2000). American psychologist Henry H. Goddard published a translation of it in 1910. The eugenics movement in the USA seized on it as a means to give them credibility in diagnosing mental retardation, and thousands of American women, most of them poor African Americans, were forcibly sterilized based on their scores on IQ tests, often without their consent or knowledge. American psychologist Lewis Terman at Stanford University revised the Binet-Simon scale, which resulted in the Stanford-Binet Intelligence Scales (1916). It became the most popular test in the United States for decades.
The many different kinds of IQ tests use a wide variety of methods. Some tests are visual, some are verbal, some tests only use abstract-reasoning problems, and some tests concentrate on arithmetic, spatial imagery, reading, vocabulary, memory or general knowledge. The psychologist Charles Spearman in 1904 made the first formal factor analysis of correlations between the tests. He found a single common factor explained the positive correlations among tests. This is an argument still accepted in principle by many psychometricians. Spearman named it g for "general factor" and labelled the smaller, specific factors or abilities for specific areas s. In any collection of IQ tests, by definition the test that best measures g is the one that has the highest correlations with all the others. Most of these g-loaded tests typically involve some form of abstract reasoning. Therefore, Spearman and others have regarded g as the (perhaps genetically determined) real essence of intelligence. This is still a common but not universally accepted view. Other factor analyses of the data, with different results, are possible. Some psychometricians regard g as a statistical artifact. One of the best measures of g is Raven's Progressive Matrices which is a test of visual reasoning.
During World War I, a way was needed to evaluate and assign recruits. This led to the rapid development of several mental tests. The testing generated controversy and much public debate. Nonverbal or "performance" tests were developed for those who could not speak English or were suspected of malingering. After the war, positive pub