Intelligence quotient

An intelligence quotient (IQ) is a total score derived from a set of <a href="/facts/Standardized_test/PkunTjfB">standardized tests</a> or subtests designed to assess <a href="/facts/Human_intelligence/vgHXwLNL">human intelligence</a>. Originally, IQ was a score obtained by dividing a person's <a href="/facts/Mental_age/Hj3pwBNA">mental age</a> score, obtained by administering an intelligence test, by the person's chronological age, both expressed in terms of years and months. The resulting fraction (<a href="/facts/Quotient/JekSq1Ko">quotient</a>) was multiplied by 100 to obtain the IQ score. For modern IQ tests, the <a href="/facts/Test_score/UBfGC72r">raw score</a> is <a href="/facts/Data_transformation_(statistics)/6wqoUa66">transformed</a> to a <a href="/facts/Normal_distribution/UapjjPyQ">normal distribution</a> with mean 100 and <a href="/facts/Standard_deviation/qSug9BRl">standard deviation</a> 15. This results in approximately two-thirds of the population scoring between IQ 85 and IQ 115 and about 2 percent each <a href="/facts/Intellectual_giftedness/4MdSLo9d">above 130</a> and <a href="/facts/Intellectual_disability/IuuYXdT1">below 70</a>.
Historically, many proponents of IQ testing have been <a href="/facts/Eugenics/e7w6aSUV">eugenicists</a> who used <a href="/facts/Pseudoscience/kdNzoLeS">pseudoscience</a> to push now-debunked views of <a href="/facts/Scientific_racism/Ug4j9v93">racial hierarchy</a> in order to justify <a href="/facts/Racial_segregation/c7QArpIR">segregation</a> and oppose <a href="/facts/Immigration/8vNxfBhT">immigration</a>. Such views are now rejected by a strong consensus of mainstream science, though fringe figures continue to promote them in <a href="/facts/Pseudo-scholarship/NK46gUNw">pseudo-scholarship</a> and popular culture. IQ scores have also been used for educational placement, <a href="/facts/IQ_classification/IfKDNaBt">assessment of intellectual ability</a>, and evaluating job applicants.
Scores from intelligence tests are estimates of intelligence. Unlike, for example, distance and mass, a concrete measure of intelligence cannot be achieved given the abstract nature of the concept of "intelligence". IQ scores have been shown to be associated with such factors as <a href="/facts/Human_nutrition/GntDW6oo">nutrition</a>, parental <a href="/facts/Socioeconomic_status/5rVhvE8b">socioeconomic status</a>, <a href="/facts/Disease/55eeQlGL">morbidity</a> and <a href="/facts/Mortality_rate/s4gmxyFV">mortality</a>, parental <a href="/facts/Social_status/X5j4NvxM">social status</a>, and <a href="/facts/Prenatal_and_perinatal_psychology/6zl5v2zU">perinatal environment</a>. While the <a href="/facts/Heritability_of_IQ/3PAa75ra">heritability of IQ</a> has been investigated for nearly a century, there is still substantial debate about the significance of heritability estimates and the mechanisms of inheritance. 
Raw scores on IQ tests for many populations have been rising at an average rate that scales to three IQ points per decade since the early 20th century, a phenomenon called the <a href="/facts/Flynn_effect/RJTsaoDb">Flynn effect</a>.

Intelligence quotient open-in-new

Intelligence quotient