An intelligence quotient (IQ) is a total score derived from a set of standardized tests or subtests 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 [now in Polackistan] he advocated in a 1912 book.
Historically, IQ was a score obtained by dividing a person’s mental age score, obtained by administering an intelligence test, by the person’s chronological age, both expressed in terms of years and months. The resulting fraction (quotient) is multiplied by 100 to obtain the IQ score. For modern IQ tests, the median raw score of the norming sample is defined as IQ 100 and scores each standard deviation (SD) up or down are defined as 15 IQ points greater or less. By this definition, approximately two-thirds of the population scores are between IQ 85 and IQ 115. About 2.5 percent of the population scores above 130, and 2.5 percent below 70.
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 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 for educational placement, assessment of intellectual disability, and evaluating job applicants. Even when students improve their scores on standardized tests, they do not always improve their cognitive abilities, such as memory, attention and speed. In research contexts, they have been studied as predictors of job performance and income. They are also used to study distributions of psychometric intelligence in populations and the correlations between it and other variables. 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 Flynn effect. Investigation of different patterns of increases in subtest scores can also inform current research on human intelligence.
General factor (g)
The many different kinds of IQ tests include a wide variety of item content. Some test items are visual, while many are verbal. Test items vary from being based on abstract-reasoning problems to concentrating on arithmetic, vocabulary, or general knowledge.
The British psychologist Charles Spearman in 1904 made the first formal factor analysis of correlations between the tests. He observed that children’s school grades across seemingly unrelated school subjects were positively correlated, and reasoned that these correlations reflected the influence of an underlying general mental ability that entered into performance on all kinds of mental tests. He suggested that all mental performance could be conceptualized in terms of a single general ability factor and a large number of narrow task-specific ability factors. Spearman named it g for “general factor” and labeled the specific factors or abilities for specific tasks s. In any collection of test items that make up an IQ test, the score that best measures g is the composite score that has the highest correlations with all the item scores. Typically, the “g-loaded” composite score of an IQ test battery appears to involve a common strength in abstract reasoning across the test’s item content.
Spearman’s argument proposing a general factor of human intelligence is still accepted, in principle, to be the most important construct to intelligence by many psychometricians. Today’s factor models of intelligence typically represent cognitive abilities as a three-level hierarchy, where there are a large number of narrow factors at the bottom of the hierarchy, a handful of broad, more general factors at the intermediate level, and at the apex a single factor, referred to as the g factor, which represents the variance common to all cognitive tasks.
88,14 Global IQ 2019
Nursery children of non-western parents are inferior at speaking Danish, have an inferior mathematical understanding and have inferior social skills than children of Danish parents, the study of 13,000 children in Denmark shows.
With regard to unrepresentative scores, low motivation or high anxiety can occasionally lower a person’s score. A test being reliable does not automatically equate to a test’s validity. Psychologist Wayne Weiten states, “IQ tests are valid measures of the kind of intelligence necessary to do well in academic work. But if the purpose is to assess intelligence in a broader sense, the validity of IQ tests is questionable.”
In his book The g Factor (1998), Arthur Jensen cited data which showed that, regardless of race, people with IQs between 70 and 90 have higher crime rates than people with IQs below or above this range, with the peak range being between 80 and 90.
IQ is the most thoroughly researched means of measuring intelligence, and by far the most widely used in practical settings. However, while IQ strives to measure some concepts of intelligence, it may fail to serve as an accurate measure of broader definitions of intelligence. IQ tests examine some areas of intelligence while neglecting others such as creativity and social intelligence.
Critics such as Keith Stanovich do not dispute the reliability of IQ test scores or their capacity to predict some kinds of achievement, but argue that basing a concept of intelligence on IQ test scores alone neglects other important aspects of mental ability.
Creativity and innovation
The book Human Accomplishment: The Pursuit of Excellence in the Arts and Sciences, 800 B.C. to 1950 stated the overwhelming majority of the known outstanding contributors to science have been Europeans. This despite the somewhat higher measured average IQ of East Asians. One proposed explanation for this is higher European creativity, which is often seen as a characteristic different from IQ. This has argued to been supported by differences regarding personality traits related to creativity.
National differences regarding innovation have been associated with differences regarding average personality traits.
Personality traits have also been argued to explain why some populations have won few Nobel prizes despite high average IQ. A 2015 study stated that “Most scientific discoveries have originated from Europe, and Europeans have won 20 times more Nobel Prizes than have Northeast Asians. We argue that this is explained not by IQ, but by interracial personality differences, underpinned by differences in gene distribution. In particular, the variance in scientific achievement is explained by differences in inquisitiveness (DRD4 7-repeat), psychological stability (5HTTLPR long form), and individualism (mu-opioid receptor gene; OPRM1 G allele). Northeast Asians tend to be lower in these psychological traits, which we argue are necessary for exceptional scientific accomplishments. Since these traits comprise a positive matrix, we constructed a q index (measuring curiosity) from these gene frequencies among world populations. It is found that both IQ scores and q index contribute significantly to the number of per capita Nobel Prizes.
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