Much of the research into the connection between genes and intelligence has focused on attempting to determine the relative roles of biological inheritance and social influence in developing intelligence. Such attempts have usually involved a combination of four methods: associations of parental intelligence with the intelligence of offspring, associations of the intelligence of siblings (brothers and sisters), comparisons of dizygotic (fraternal) twins and monozygotic (identical) twins, and adoption studies.
To the extent that mental qualities are inherited, one should expect blood relatives to share these qualities with each other more than with nonrelatives. In an article published in 1981 in the journal Science, T. J. Bouchard, Jr., and Matt McGue examined studies that looked at statistical relationships of intellectual abilities among family members. These studies did reveal strong associations between mental capacities of parents and children and strong associations among the mental capacities of siblings. Further, if genes are involved in establishing mental abilities, one should expect that the more genes related people share, the more similar they will be in intelligence. Studies have indicated that fraternal twins are only slightly more similar to each other than are nontwin siblings. Identical twins, developing from a single egg with identical genetic material, have even more in...
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The Problem of Defining and Measuring IntelligenceIntelligence testing (Genetics & Inherited Conditions)
Debates over genetic links to intelligence are complicated by the problem of precisely defining and accurately measuring intelligence. It may be that abilities to build houses, draw, play music, or understand complex mathematical procedures are inherited as well as learned. Which of these abilities, however, constitute intelligence? Because of this debate, some people, such as Harvard psychologist Howard Gardner, have argued that there is no single quality of intelligence but rather multiple forms of intelligence.
If there is no single ability that can be labeled “intelligence,” this means that one cannot measure intelligence or determine the extent to which general intellectual ability may be genetic in character. An intelligence quotient (IQ), the measure of intelligence most commonly used to study genetic links to intellectual ability, is based on the view that there is a great deal of overlap among various mental traits. Although a given individual may be skilled at music or writing and poor at mathematics, on average, people who are proficient in one area tend to be talented in other areas. Proponents of IQ measures argue that this overlap exists because there is a single, underlying, general intelligence that affects how people score on tests of various kinds of mental abilities. The opponents of IQ measures counter that even if one can speak of intelligence...
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Impact and Applications (Genetics & Inherited Conditions)
The passing of mental abilities from parents to children by genetic inheritance is a politically controversial issue because genetic theories of intelligence may be used to justify existing social inequalities. Social and economic inequalities among racial groups, for example, have been explained as differences among groups in inherited intelligence levels. During the nineteenth century, defenders of slavery claimed that black slaves were by nature less intelligent than the white people who held them in slavery. After World War I, the Princeton University psychologist C. C. Brigham concluded from results of army IQ tests that southern European immigrants had lower levels of inherited intelligence than native-born Americans and that blacks had even more limited intelligence. White supremacists and segregationists used Brigham’s results to justify limiting the access of blacks to higher education and other opportunities for advancement. In 1969, Berkeley psychologist Arthur R. Jensen touched off a storm of debate when he published an article that suggested that differences between black and white children in educational success were caused in part by genetic variations in mental ability.
Wealth and poverty, even within racial and ethnic groups, have been explained as consequences of inherited intelligence. Harvard psychologist Richard Herrnstein and social critic Charles Murray have argued that American society has...
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Further Reading (Genetics & Inherited Conditions)
Bock, Gregory R., Jamie A. Goode, and Kate Webb, eds. The Nature of Intelligence. New York: John Wiley and Sons, 2001. Presents the debate between evolutionary psychologists, who argue against general intelligence and for an intelligence that develops and evolves based on particular, extraspecies domains, and behavior geneticists, who believe general intelligence is fundamental and who focus their work on intraspecies differences. Illustrations, bibliography, and index.
Devlin, Bernie, et al. Intelligence, Genes, and Success: Scientists Respond to “The Bell Curve.” New York: Springer, 1997. Presents a scientific and statistical reinterpretation of The Bell Curve’s claims about the heritability of intelligence and about IQ and social success. Bibliography, index.
Fish, Jefferson M., ed. Race and Intelligence: Separating Science from Myth. Mahwah, N.J.: Lawrence Erlbaum, 2002. An interdisciplinary collection disputing race as a biological category, arguing that there is no general or single intelligence and that cognitive ability is shaped through education. Bibliography, index.
Fraser, Steven, ed. The “Bell Curve” Wars: Race, Intelligence, and the Future of America. New York: Basic Books, 1995. Scholars from a variety of disciplines and backgrounds provide a brief, critical response to the book by Herrnstein and Murray. Bibliography.
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Web Sites of Interest (Genetics & Inherited Conditions)
Great Ideas in Personality, Intelligence. http://www.personalityresearch.org/intelligence.html. G. Scott Acton, a psychology professor at the Rochester Institute of Technology, compiled this Web site dealing with scientific research programs in human personality. The site includes a page describing various theories of intelligence and links to additional resources.
Human Intelligence. http://www.indiana.edu/~intell/index.shtml. This site, sponsored by Indiana University, features biographies of people who have influenced the development of intelligence theory and testing, along with articles examining current controversies related to human intelligence.
Scientific American. “The General Intelligence Factor.”. http://www.psych.utoronto.ca/users/reingold/courses/intelligence/cache/1198gottfred.html. In this online magazine article, Linda S. Gottfredson, professor of education and codirector of the Delaware-Johns Hopkins Project for the Study of Intelligence and Society, argues that a single factor for intelligence, called g, can be measured with IQ tests and can predict success in life.
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Introduction (Psychology and Mental Health)
The idea that human beings differ in their capacity to adapt to their environments, to learn from experience, to exercise various skills, and in general to succeed at various endeavors has existed since ancient times. Intelligence is the attribute most often singled out as responsible for successful adaptations. Up to the end of the nineteenth century, notions about what constitutes intelligence and how differences in intelligence arise were mostly speculative. In the late nineteenth century, several trends converged to bring about an event that would change the way in which intelligence was seen and dramatically influence the way it would be studied. That event, which occurred in 1905, was the publication of the first useful instrument for measuring intelligence, the Binet-Simon scale, which was developed in France by Alfred Binet and Théodore Simon.
Although the development of intelligence tests was a great technological accomplishment, it occurred, in a sense, somewhat prematurely, before much scientific attention had been paid to the concept of intelligence. This circumstance tied the issue of defining intelligence and a large part of the research into its nature and origins to the limitations of the tests that had been devised. In fact, the working definition of intelligence that many psychologists have used either explicitly or implicitly in their scientific and applied pursuits is the one expressed by Edwin Boring in...
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Changing Definitions (Psychology and Mental Health)
Boring’s semifacetious definition of intelligence may be the best known and most criticized one, but it is only one among many that have been offered. Most experts in the field have defined the concept at least once in their careers. Two of the most frequently cited and influential definitions are the ones provided by Binet himself and by David Wechsler, author of a series of “second-generation” individual intelligence tests that overtook the Binet scales in terms of the frequency with which they are used. Binet believed that the essential activities of intelligence are to judge well, to comprehend well, and to reason well. He stated that intelligent thought is characterized by direction, knowing what to do and how to do it; by adaptation, the capacity to monitor one’s strategies for attaining a desired end; and by criticism, the power to evaluate and control one’s behavior. In 1975, almost sixty-five years after Binet’s death, Wechsler defined intelligence, not dissimilarly, as the global capacity of the individual to act purposefully, to think rationally, and to deal effectively with the environment.
In addition to the testing experts (psychometricians), developmental, learning, and cognitive psychologists, among others, are also vitally interested in the concept of intelligence. Specialists in each of these subfields emphasize different aspects of it in their definitions and research.
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Factor Analysis (Psychology and Mental Health)
The lack of a universally accepted definition has not deterred continuous theorizing and research on the concept of intelligence. The central issue that has dominated theoretical models of intelligence is the question of whether it is a single, global ability or a collection of specialized abilities. This debate, started in England by Charles Spearman, is based on research that uses the correlations among various measures of abilities and, in particular, the method of factor analysis, which was also pioneered by Spearman. As early as 1904, Spearman, having examined the patterns of correlation coefficients among tests of sensory discrimination and estimates of intelligence, proposed that all mental functions are the result of a single general factor, which he later designated g. Spearman equated g with the ability to grasp and apply relations. He also allowed for the fact that most tasks require unique abilities, and he named those s, or specific, factors. According to Spearman, to the extent that performance on tasks was positively correlated, the correlation was attributable to the presence of g, whereas the presence of specific factors tended to lower the correlation between measures of performance on different tasks.
By 1927, Spearman had modified his theory to allow for the existence of an intermediate class of factors, known as group factors, which were neither as universal as...
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Organizational Models (Psychology and Mental Health)
As the search for distinct intellectual factors progressed, their number multiplied, and so did the number of models devised to organize them. One type of scheme, used by Cyril Burt, Philip E. Vernon, and others, is a hierarchical arrangement of factors. In these models, Spearman’s g factor is placed at the top of a pyramid and the specific factors are placed at the bottom; in between, there are one or more levels of group factors selected in terms of their breadth and arranged according to their interrelationships with the more general factors above them and the more specific factors below them.
In Vernon’s scheme, for example, the ability to change a tire might be classified as a specific factor at the base of the pyramid, located underneath an intermediate group factor labeled mechanical information, which in turn would be under one of the two major group factors identified by Vernon as the main subdivisions under g—namely, the practical-mechanical factor. The hierarchical scheme for organizing mental abilities is a useful device that is endorsed by many psychologists on both sides of the Atlantic. It recognizes that very few tasks are so simple as to require a single skill for successful performance, that many intellectual functions share some common elements, and that some abilities play a more pivotal role than others in the performance of culturally valued activities.
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Competence and Self-Management (Psychology and Mental Health)
Contemporary theorists in the area of intelligence have tried to avoid the reliance on factor analysis and existing tests that have limited traditional research and have tried different approaches to the subject. For example, Howard Gardner, in his 1983 book Frames of Mind: The Theory of Multiple Intelligences, starts with the premises that the essence of intelligence is competence and that there are several distinct areas in which human beings can demonstrate competence. Based on a wide-ranging review of evidence from many scientific fields and sources, Gardner designated seven areas of competence as separate and relatively independent “intelligences.” In his 1993 work Multiple Intelligences, Gardner revised his theory to include an eighth type of intelligence. This set of attributes comprises verbal, mathematical, spatial, bodily/ kinesthetic, musical, interpersonal, intrapersonal, and naturalist skills.
Another theory is the one proposed by Robert Sternberg in his 1985 book Beyond IQ: A Triarchic Theory of Human Intelligence. Sternberg defines intelligence, broadly, as mental self-management and stresses the “real-world,” in addition to the academic, aspects of the concept. He believes that intelligent behavior consists of purposively adapting to, selecting, and shaping one’s environment and that both culture and personality play significant roles in such behavior....
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Intelligence and Environment (Psychology and Mental Health)
Theories of intelligence are still grappling with the issues of defining its nature and composition. Generally, newer theories do not represent radical departures from the past. They do, however, emphasize examining intelligence in relation to the variety of environments in which people actually live rather than to only academic or laboratory environments. Moreover, many investigators, especially those in cognitive psychology, are more interested in breaking down and replicating the steps involved in information processing and problem solving than they are in enumerating factors or settling on a single definition of intelligence. These trends hold the promise of moving the work in the field in the direction of devising new ways to teach people to understand, evaluate, and deal with their environments more intelligently instead of simply measuring how well they do on intelligence tests. In their 1998 article “Teaching Triarchically Improves School Achievement,” Sternberg and his colleagues note that teaching or training interventions can be linked directly to components of intelligence. Motivation also plays a role. In their 2000 article “Intrinsic and Extrinsic Motivation,” Richard Ryan and Edward Deci provide a review of contemporary thinking about intrinsic and extrinsic motivation. The authors suggest that the use of motivational strategies should promote student self-determination.
The most heated of...
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Sources for Further Study (Psychology and Mental Health)
Fancher, Raymond E. The Intelligence Men: Makers of the IQ Controversy. New York: W. W. Norton, 1987. Presents the history of the various debates on intelligence in a highly readable fashion. The lives and ideas of the pioneers in the field, such as Binet and Galton, are described in some detail.
Flynn, James R. What Is Intelligence? Beyond the Flynn Effect. New York: Cambridge University Press, 2009. Flynn collected and studied data that show that the developed world experienced huge gains in IQ in the twentieth century. He attributes this to the growth in abstract scientific thinking.
Gardner, Howard. Frames of Mind: The Theory of Multiple Intelligences. New York: Basic Books, 2004. Gardner’s description of the talents he designates as “intelligences” and explanation of the reasons for his selections provide a fascinating introduction to many of the most intriguing aspects of the field, including the extremes of prodigies and idiots savants.
__________. Multiple Intelligences: The Theory in Practice. New York: Basic Books, 2006. Gardner’s update of his original theory of multiple intelligences adds an eighth intelligence to the set.
Guilford, Joy Paul. The Nature of Human Intelligence. New York: McGraw-Hill, 1967. Guilford describes the foundation of his theory of the structure of the intellect and in the process reviews the history of...
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Intelligence (Encyclopedia of Psychology)
An abstract concept whose definition continually evolves and often depends upon current social values as much as scientific ideas. Modern definitions refer to a variety of mental capabilities, including the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly, and learn from experience as well as the potential to do so.
Several theories about intelligence emerged in the 20th century and with them debate about the nature of intelligence, whether it is hereditary, environmental or both. As methods developed to assess intelligence, theorizing occurred about the measurability of intelligence, its accuracy and this field known as psychometrics. As the 20th century drew to a close, publication of The Bell Curve by Richard J. Herrnstein and Charles Murray in 1994 stirred the controversy. Their findings pointed to links between social class, race, and IQ scores, despite questions by many about the validity of IQ tests as a measurement of intelligence or a predictor of achievement and success.
Part of the problem regarding intelligence stems from the fact that nobody has adequately defined what intelligence really means. In everyday life, we have a general understanding that some people are "smart," but when we try to define "smart" precisely, we often have difficulty because a person...
(The entire section is 1321 words.)
Intelligence (Encyclopedia of Children's Health)
Intelligence is an abstract concept whose definition continually evolves and often depends upon current social values as much as scientific ideas. Modern definitions refer to a variety of mental capabilities, including the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly, and learn from experience, as well as the potential to do these things.
Several theories about intelligence emerged in the twentieth century and with them debate about the nature of intelligence and whether it determined by hereditary factors, the environment, or both. As methods developed to assess intelligence, experts theorized about the measurability of intelligence, its accuracy, and the field known as psychometrics, a branch of psychology dealing with the measurement of mental traits, capacities, and processes. Publication in 1994 of The Bell Curve: Intelligence and Class Structure in American Life by Richard J. Herrnstein and Charles Murray stirred the controversy. Their findings pointed to links between social class, race, and intelligence quotient (IQ) scores, despite questions by many about the validity of IQ tests as a measurement of intelligence or a predictor of achievement and success....
(The entire section is 3093 words.)