High intelligence is, in psychometric categories, an intelligence quotient (IQ) of 130 or higher; more generally, a superior ability to receive and retain information, and apply it to new situations through a process of logical reasoning and problem solving.
The English word intelligence comes from the Latin verb intelligere, which means “to perceive or recognize” and “to understand or comprehend.” High intelligence is also called intellectual giftedness.
Humans have long recognized that people differ in their mental abilities in degree as well as type; as stated in the 1996 report by the American Psychological Association on the nature of intelligence: “Individuals differ from one another in their ability to understand complex ideas, to adapt effectively to the environment, to learn from experience, to engage in various forms of reasoning, to overcome obstacles by taking thought.” This recognition, however, did not become a subject of systematic scientific inquiry until the end of the eighteenth century, when the discovery of the so-called Wild Boy of Aveyron (c.1788–1828), a French feral child, led to research about the relationship between education and human intelligence. In the nineteenth century, Charles Darwin's (1809–1882) theory of evolution and the studies of his half-cousin Francis Galton (1822–1911) regarding the hereditary component of human intelligence encouraged more specific studies of high intelligence and other exceptional gifts, such as musical or artistic talent. Although Galton studied the statistical distribution of mathematics scores of officer candidates in the British army and is considered the founder of psychometry, he did not devise an intelligence test as the term is now understood.
The first practical test for measuring differences in intelligence was invented by two French psychologists, Alfred Binet (1857–1911) and The´ odore Simon (1872–1961). The Binet-Simon Intelligence Scales, published in 1905, set the standard for contemporary measures of intelligence in that they arranged test items in order of difficulty and took into account the differences in intellectual ability of children of different ages. In the United States, the first psychologist to use Binet and Simon's work in studying intellectually gifted children was Lewis Terman (1877–1956), best known for his revision of the Stanford-Binet IQ Test and for his longitudinal study of children with high intelligence, the Genetic Studies of Genius (also called the Terman Study of the Gifted).
As of 2015, Wechsler classifications for IQ scores were as follows:
One aspect of high intelligence that is often not understood is that at the upper reaches of the IQ distribution—persons who are 3 or 4 SDs above average—exceptional abilities tend to be much more specialized. A highly intelligent person with an IQ of 130 is usually about equally competent on all the subtests of an IQ test, whereas a person with an IQ of 160 (4 SDs above average) may be extremely competent at linguistic tasks but less competent in mathematics—or the reverse. Another way of describing this phenomenon is that the concept of general intelligence breaks down around IQ 130. It is generally recognized that standard IQ tests are useful chiefly in identifying whether a child has high intelligence rather than in distinguishing among levels of exceptional intelligence; the Wechsler tests have a score ceiling of 160.
Heredity has been understood to be a significant factor in high intelligence since Galton's day. When the mapping of the human genome was completed in 2003, a number of geneticists began to search for specific genes associated with intelligence. No single gene had emerged as uniquely important; molecular biologists considered intelligence in humans to be polygenic, or influenced by a number of different genes. Another finding is that the heritability of intelligence increases with age, from about 20% in infancy to 80% in late adulthood.
One aspect of heredity that has attracted attention is the significance of birth order. Within a given family, eldest or only children tend to score higher on IQ tests than later-born siblings. Psychologists disagree about the significance of these findings or the reasons for them; one suggestion is that the first-born or only child receives the parents’ undivided attention for a period of time and that firstborns or only children are exposed to adult language skills earlier in life. Another explanation is that parents are more likely to devote a larger portion of their financial resources to the education of firstborn children.
In the United States, the influence of environment on high intelligence is a politically sensitive issue because of discrepancies among various racial and ethnic groups in the proportion of their populations identified as gifted. Factors that are known to affect group differences include nutrition, length of schooling, educational interventions, and family environments as well as cultural differences among groups. Some ethnic groups prize intellectual achievement while others emphasize athletic ability or physical strength. Some families urge their children to excel while others discourage gifted members from surpassing other family members.
Another complication is gender roles. Most IQ tests are constructed to eliminate sex differences. While the influence of sex hormones on high intelligence is debated—there is some evidence that males perform at higher levels in mathematics and females excel in linguistic skills—there is little dispute that gender stereotypes in the surrounding culture can hamper both males and females in using their intelligence. Boys may find themselves stigmatized as geeks or nerds while gifted girls may be labeled as unfeminine or unattractive.
Persons with high intelligence must live among other people; that is, interact with others in school and the larger society as well as develop as individuals. There is a large body of literature on the difficulties persons of high intelligence may encounter in the course of growing up. Difficulties of gifted children in social adjustment range from shyness and a preference for solitude to heightened emotional sensitivity to teasing to problems understanding why other children are not as quick or knowledgeable as they are. One reason for these difficulties is that intellectual development in gifted children outpaces physical and social development, and parents and teachers must recognize these different rates of development in order to avoid misdiagnosing the gifted child as having a mood or personality disorder.
Although highly intelligent persons are often stereotyped as psychologically maladjusted or prone to mental disorders, there is no evidence that they are more likely to commit suicide, have nervous breakdowns, or develop psychoses. Terman's studies of gifted children indicated that most people of high intelligence develop above-average social skills by the time they are adults.
High intelligence is a major social as well as personal issue because it is an increasingly important factor in the educational and occupational future of these children. Although Binet and Simon devised their test in order to identify and help children who were slow learners, Terman regarded intelligence testing as a tool for classifying children and putting them on the vocational track most appropriate to their abilities. This use of intelligence measurement as a social sorting mechanism has had a number of consequences in the United States, especially increasing parents’ anxiety about their children's test scores.
One consequence of psychologists’ interest in identifying children with high intelligence was the eugenics movement of the nineteenth and early twentieth centuries. The recognition that high intelligence has a genetic component led Galton, Terman, Thorndike, and other psychologists involved in intelligence testing to become ardent proponents of eugenics. The negative political consequences of the eugenics movement, from the forced sterilization of those considered unfit in the United States to their euthanasia in Nazi Germany, is another reason for many people's concern that identification of the highly intelligent leads to devaluation of less gifted others.
Another consequence of intelligence testing has been the emergence of a so-called cognitive elite— that is, a class of highly intelligent and well-educated people who are increasingly separated from the mass of the U.S. population by their tendency to marry only among themselves, enter a relatively small number of occupations, and live in neighborhoods that set them apart physically from people of lesser cognitive abilities. The potential consequences of the stratification of U.S. society on the basis of intelligence have provoked intense debate among psychologists as well as political scientists since the early 2000s.
See also Eugenics ; Terman, Lewis; Savant syndrome .
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