IQ

For other uses, see IQ (disambiguation).

IQ, an abbreviation for "intelligence quotient", is a score derived from a set of standardized tests that were developed with the purpose of measuring a person's cognitive abilities ("intelligence") in relation to one's age group. It is expressed as a number normalized so that the average IQ in an age group is 100 — in other words an individual scoring 115 is above-average when compared to similarly aged people. It is usual, but not invariable, practice to standardise so that the standard deviation (σ) of scores is 15. Tests are designed so that the distribution of IQ scores is more-or-less Gaussian, that is to say that it follows the bell curve. Scores on a given test in a given population have tended to rise across time throughout the history of IQ testing (the Flynn effect), so that tests need repeated renormalisation if these standards are to be maintained.

Contents

Overview

IQ scores are generally taken as an objective measure of intelligence. Because intelligence is difficult to define, the definition "Intelligence is what the IQ test measures" has been seriously proposed.

Modern ability tests produce scores for different areas (e.g., language fluency, three-dimensional thinking, etc.), with the summary score calculated as a some general measure, whose significance is disputed. Significantly, individual subtest scores correlate highly: with one another, and over diverse tests.

While it might be argued that IQ tests encode their creator's beliefs about what constitutes intelligence, analyses of an individual's scores on a wide variety of tests will reveal that they all measure a single common factor and various factors that are specific to each test. This kind of analysis has led to the theory that underlying these disparate cognitive tasks is a single factor, termed the g factor, that represents the common-sense concept of intelligence.

Opponents argue that it is much more useful to know which are the strengths and weaknesses of a person than to know that he or she holds a measureable superlative on n percent of the populace in some "general intelligence" measure. Such opponents often cite the example of two people with the same overall IQ score but very different ability profiles. However, most people have highly balanced ability profiles. Differences in subscores are greatest among the most intelligent, which may lead them to this misconception.

Others argue that IQ testing is unnecessarily narrow and have proposed wider testing that covers emotional/social intelligence, creativity, artistic intelligence, etc. Proponents of this viewpoint often say "one's IQ is merely a measure of how good one is at doing IQ tests."

The modern field of intelligence testing began with the Stanford-Binet test. It is worth noting that Alfred Binet, who created the IQ test in 1904, was aiming to identify students who could benefit from extra help in school: his assumption was that lower IQ indicated the need for more teaching, not an inability to learn. Indeed, this interpretation is still held by modern experts. The term "intelligence quotient" comes from this test, in which each student's score was the quotient of his or her tested academic age with his or her actual age. Modern IQ tests do not calculate scores in this way, but the term IQ is still in common use.

(The following numbers apply to IQ scales with a standard deviation σ = 15.) Scores between 85 and 115 are considered average—so a person scoring 95 is simply average, not below-average. The "normal" range, or range between -2 and +2 standard deviations from the mean, is between 70 and 130. A score below 70 is an indicator of mental retardation, and a score above 130 is an indicator of intellectual giftedness.

Some writers say that such scores outside the range 55 to 145 are essentially meaningless because there have not been enough people tested in those ranges to make statistically sound statements. Moreover, at such extreme values, the normal distribution is a less accurate estimate of the IQ distribution.

Sex and IQ

Most IQ tests are designed so that the average IQs of males and females are equal. However, men tend to score higher in the parts of the test that cover spatial and quantitative abilities, and women generally score higher in the verbal sections. Some research has shown that the variance in mens' IQ scores is greater than the variance among womens', as seen in other cognitive test scores. This is why more men than women are found in both very high and very low scoring groups.

Race and IQ

The Bell Curve, published in 1994 by Richard Herrnstein and Charles Murray, created great controversy among the scientific community and the public by suggesting that the average IQ of races differ. They claim that the mean IQ scores of African Americans are one standard deviation (15 points) lower than those of European Americans, and they attribute between 40 - 80% to genetic factors. Critics publicly claimed that their evidence for a 'genetic' factor was exacerbated by the lack of account for some of the social factors believed to determine IQ, such as economic status, stress in environment, and access to education. As a result of the book's controversial claims, Murray received bomb threats and was denounced as a racist by a number of public figures, including Jesse Jackson. In contrast, the majority of intelligence researchers support the non-policy research conclusions made in the Bell Curve (see the Wall Street Journal: "Mainstream Science on Intelligence" below). The book also argues that East Asians and Jews generally have higher IQ than all other races.

Arthur Jensen was one of the earliest researchers to propose that the IQ gap between blacks and whites is best explained by a hypothesis that attributes at least some of the cause to genetic factors. His 1969 paper in "Harvard Education Review" also stated that compensatory education was not very effective and that "genetic differences were more important than cultural or socioeconomic differences in explaining individual differences in IQ within the white population."

Many compilations of average IQ by country place East Asian countries at the top of such lists. Some argue that this is in part attributed to some IQ tests' inherent bias towards testing spatial reasoning. They argue that pictographic languages like Chinese or Japanese develop spatial reasoning better than Roman languages prevalent in Europe and America. The same reasoning has been used to explain why students from Asia-Pacific countries (eg Singapore, South Korea) tend to score better than average in tests of mathematics. Some argue that the East Asian advantage can also be explained by more rigorous education programs. Opponents of these interpretations point out that people of East Asian descent who are born and educated in the United States and primarily speak English score better on average on IQ tests than their white peers.

Opposition to IQ testing

Many scientists disagree with the practice of psychometrics in general. In The Mismeasure of Man, Professor Stephen Jay Gould strongly disputes the basis of psychometrics as a form of scientific racism, objecting that it is:

...the abstraction of intelligence as a single entity, its location within the brain, its quantification as one number for each individual, and the use of these numbers to rank people in a single series of worthiness, invariably to find that oppressed and disadvantaged groups--races, classes, or sexes--are innately inferior and deserve their status. (pp. 24-25).

Later editions of the book include a refutation of The Bell Curve.

While public discourse on IQ testing is generally inflammatory, IQ tests are used ubiquitously in research and education. In general, there is a disparity between the public perception of IQ testing and the opinion of intelligence researchers.

Some proponents of IQ have pointed to a number of studies showing a fairly close correlation between IQ and various life outcomes, particularly income. Research in Scotland (http://news.bbc.co.uk/hi/english/health/newsid_1260000/1260794.stm) has shown that a 15-point lower IQ meant people had a fifth less chance of seeing their 76th birthday, while those with a 30-point disadvantage were 37% less likely than those with a higher IQ to live that long. Research by Charles Murray on siblings (http://www.eugenics.net/papers/murray.html) has shown that there is a strong correlation between IQ and earned income. The controversial study IQ and the Wealth of Nations claims to show that the wealth of a nation correlates closely to its IQ score.

SAT

A study found that SAT was a de facto IQ test and SAT scores could be used in lieu of IQ scores for the purpose of psychological investigations. Mensa, a high IQ society, accepts individuals who scored at the 98th percentile, or 1300+ on tests scored prior to 30 September 1974, and 1250+ on tests scored after that date through 31 January 1994. After the test was recentered in 1995, Mensa decided that the SAT was no longer an IQ test and does not accept SAT scores of 1300+ (renormed 98th percentile) from 1995 onward for admission. However, tables to correlate (both historical and modern) SAT scores to IQ do exist, and can be found here. (http://members.shaw.ca/delajara/GREIQ.html)

Online IQ tests

Although such tests have become wildly popular with the explosion of the Internet in recent years, there is great reason to believe that these IQ tests are highly inaccurate in their estimation of one's IQ. For example, by inputting random answers on one particular IQ test, an IQ of roughly 80 is obtained. Comparing results among a large set of people shows a common factor—most scores are above 110. Most of these websites attempt to sell certificates showing test results. It is therefore recommended not to take online IQ tests as a true judge of one's IQ.

See also

External links


da:Intelligenskvotient de:Intelligenzquotient fr:Quotient intellectuel ja:知能指数 nl:Intelligentiequotiënt pl:Iloraz_inteligencji fi:Älykkyysosamäärä sv:IQ

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