IQ
Definition and History
Intelligence quotient, or IQ, is a total score derived from several standardized tests designed to assess human intelligence. The abbreviation "IQ" was coined by the psychologist William Stern for the German term Intelligenzquotient, his term for a scoring method for intelligence tests at University of Breslau he advocated in a 1912 book.
Measurement of IQ
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.
IQ Tests
IQ tests are standardized to a median score of 100 and a standard deviation of 15. The Stanford-Binet and the Wechsler Adult Intelligence Scale (WAIS) are two of the most commonly used IQ tests.
IQ and Genetics
The heritability of IQ for adults is between 57% and 73% with some more-recent estimates as high as 80% and 86%. IQ goes from being weakly correlated with genetics, for children, to being strongly correlated with genetics for late teens and adults. The heritability of IQ increases with age and reaches an asymptote at 18–20 years of age and continues at that level well into adulthood.
IQ and Environment
Environmental factors play a role in the development of intelligence and can have significant effects on the IQ of individuals. Factors such as prenatal environment, nutrition, education, and social environment have all been found to influence IQ.
IQ and Society
IQ classifications were used to label individuals and predict their potential for success in society. However, such classifications are now considered controversial and often carry negative connotations. IQ tests are now predominantly used in educational and clinical settings.
Criticisms and Views on IQ
There are criticisms of IQ, primarily that it is an oversimplification of intelligence and does not fully account for different types of intelligence. Moreover, there are questions about the culture-fairness of IQ tests.