Introduction
In 1969, educational psychologist Arthur R. Jensen published an article in the Harvard Educational Review entitled “How Much Can We Boost I.Q. and Scholastic Achievement?” He attempted to explain the consistent finding that whites, on the average, outperform blacks by about fifteen points on intelligence quotient (IQ) tests. His major conclusion was that racial differences in intelligence are primarily attributable to heredity and that whites, as a racial group, are born with abilities superior to those of blacks.
Jensen, along with William Shockley, presents the hereditarian hypothesis of intelligence. It argues that some people are born smarter than others and that this fact cannot be changed with training, education, or any alteration in the environment. Because they believe that African Americans as a group are not as smart as whites, they suggest that special programs, such as Head Start, which are designed to help disadvantaged children improve in school achievement, are doomed to fail.
In contrast to the hereditarians, Urie Bronfenbrenner and Ashley Montagu can be described as environmentalists. They believe that although intelligence has some genetic component, as do all human characteristics, the expression of intelligent behavior is defined, determined, and developed within a specific cultural context. Therefore, what people choose to call intelligence is primarily caused by the interaction of genetics with environmental influences. Environmentalists believe that a person can improve in his or her intellectual functioning with sufficient changes in environment.
Richard Herrnstein and Charles Murray’s
The Bell Curve (1994) reopened the issue of heredity versus environment in the attainment of intelligence. The authors argue that whites are inherently superior to African Americans in IQ levels, presenting a mass of statistical evidence to support their position. Critics of The Bell Curve attack it on a number of fronts. There is a failure to separate hereditary from genetic variables. The definition of race proves a difficult one. The IQ tests themselves come into the same culture bias category. The statistical tests hide more than they reveal. There is difficulty replicating Herrnstein and Murray’s results. The defects mount up rather quickly.
Much of the hereditarian argument is based on two types of studies: those comparing IQ test performance of twins and those of adopted children. Because identical twins have the same genetic endowment, it is thought that any differences observed between them should be attributable to the effects of the environment. Hereditarians also suggest that one should observe more similarities in the IQs of parents and their biological children (because they share genes) than between parents and adopted children (who are biologically unrelated and therefore share no genes).
Statistical formulas are applied to comparisons between family members’ IQs to determine the relative contributions of heredity and environment. Using this method, Sir Cyril Burt in 1958 reported a heritability estimate of 0.93. This means that 93 percent of the variability in intelligence could be explained genetically. People have also interpreted this to mean that 93 percent of the intelligence level is inherited. Jensen has more recently reported heritability estimates of 0.80 and 0.67, depending on what formula is used. Hereditarians have also pointed out that when they compare African Americans and whites from similar environments (the same educational level, income level, or occupation), the reported IQ differences remain. This, they argue, supports their view that heredity is more important in determining intelligence. The same arguments have been made for the work of Herrnstein and Murray.
For environmentalists, it is not so much the reported IQ differences between different racial groups that are in question. Of more concern are the basic assumptions made by the hereditarians and the reasons they give for the reported differences. Not surprisingly, environmentalists challenge the hereditarian arguments on several levels. First, they point out that there is no evidence of the existence of an “intelligence” gene or set of genes. They say that scientists have been unsuccessful in distinguishing the genetic from the environmental contributions to intelligence.
Environmentalists also refute the assumption that IQ tests adequately measure intelligence. Although IQ has been noted to be a good predictor of success in school, it turns out to have little relationship to economic success in life. S. E. Luria reports an analysis that shows that the son of a white businessman with an IQ of 90 has a greater chance of success than an African American boy with an IQ of 120. This example calls into question what actually is being assessed. It is not at all clear that “intelligence” is being measured, especially since there is no generally accepted definition of intelligence among social scientists.
The definition of race is also problematic. Although most people may classify people into several racial groups, Montagu and many other social scientists agree that race is a pseudoscientific concept, used as a social or political category to assign social status and to subordinate nonwhite populations. Because of intermingling among different cultural groups, it is also difficult to identify strict biological boundaries for race, which in turn makes genetic interpretations of racial comparisons of IQ differences much less meaningful.
In addition to questioning what IQ tests measure, many psychologists have criticized IQ tests as being biased against individuals who are culturally different from the mainstream group (whites) and who have not assimilated the white, middle-class norms on which the tests were based. Tests developed in one culture may not adequately measure the abilities and aptitude of people from another culture, especially if the two cultures emphasize different skills, ways of solving problems, and ways of understanding the world.
Environmentalists have also criticized the research and statistical techniques used by the hereditarians. It is now widely acknowledged that the data reported by Burt, on which Jensen heavily relied, were false. In many different studies, he came up with the same figures (to the third decimal point) for the similarities between IQ scores for twins. This is statistically impossible. He also did not take into account how other variables, such as age and gender, might have produced higher IQ values in the twins he studied. Rather, he assumed that they shared genes for intelligence.
It is also charged that the concept of heritability is misunderstood by the hereditarians. This is a statistic that applies to groups, not to individuals. If one states that the heritability estimate of a group of IQ scores is 0.80, that does not mean that 80 percent of each IQ score is attributable to genetics, but that 80 percent of the difference in the group of scores can be attributed to genetic variation. Therefore, according to the environmentalists, it is incorrect for hereditarians to establish heritability within one group (such as white children) and then apply that figure to a different racial group (such as African American children).
Consequences of Various Positions
Several examples may help clarify the relationships between heredity, environment, and characteristics such as IQ. The first example involves a highly heritable characteristic, height. A farmer has two fields, one rich in nutrients (field A) and the other barren (field B). The farmer takes seeds from a bag that has considerable genetic variety, plants them in the two fields, and cares for the two fields of crops equally well. After several weeks, the plants are measured. The farmer finds that within field A, some plants are taller than others in the same field. Since all these plants had the same growing environment, the variation could be attributed to the genetic differences in the seeds planted. The same would be the case with the plants in field B.
The farmer also finds differences between the two fields. The plants in field A are taller than the plants in field B, because of the richer soil in which they grew. The difference in the average heights of the plants is attributable to the quality of the growing environment, even though the genetic variation (heritability) within field A may be the same as that within field B. This same principle applies to IQ scores of different human groups.
Taking the example further, the farmer might call a chemist to test the soil. If the chemist was able to determine all the essential missing nutrients, the farmer could add them to the soil in field B for the next season. The second batch of plants would grow larger, with the average height being similar to the average height of plants in field A. Similarly, if one is comparing African Americans and whites, or any number of racial groups, on a characteristic such as IQ test scores, it is important to understand that unless the groups have equivalent growing environments (social, political, economic, educational, and so on), differences between the groups cannot be easily traced to heredity.
As another example, one might be to take a set of identical twins who were born in Chicago, separate them at birth, and place one of the twins in the Kung desert community in Africa. The life experiences of the twin in Africa would differ significantly from those of his Chicago counterpart because of the differences in diet, climate, and other relevant factors required for existence and survival in the two environments. The twin in Africa would have a different language and number system; drawing and writing would likely not be an important part of daily life. Therefore, if one were to use existing IQ tests, one would have to translate them from English to the Kung language so that they could be understood. The translation might not truly capture the meaning of all the questions and tasks, which might interfere with the Kung twin’s understanding of what was being asked of him. More problems would arise when the Kung twin is asked to interpret drawings or to copy figures, since he would not be very familiar with these activities.
It is likely that the Kung twin would perform poorly on the translated IQ test, because it does not reflect what is emphasized and valued in his society. Rather, it is based on the schooling in the society in which the Chicago twin lives. This does not mean that the Kung twin is less intelligent than his Chicago twin. Similarly, the Chicago twin would do poorly on a test developed from the experience of Kung culture, because the !Kung test would emphasize skills such as building shelter, finding water, and other activities that are not important for survival in Chicago. In this case, the Kung test would not adequately measure the ability of the Chicago twin.
Studies done by psychologist Sandra Scarr show that evidence for a genetic basis for racial differences in IQ is far from clear. She looked at the IQ scores of African American children who were born into working-class families but were adopted and reared by white middle-class families. The IQ scores of these children were close to the national average and were almost 10 to 20 points higher than would have been expected had they remained in their birth homes.
Change in children’s environments seems to be a critical factor in enhancing their ability to perform on the IQ tests, as seen in the research done by Scarr. Bronfenbrenner found similar results. He examined a dozen studies that looked at early intervention in children’s lives; he found that whenever it was possible to change the environment positively, children’s scores on IQ tests increased.
Historical Development of Racial Context
The notion of inherited differences is an ancient one; however, the concept of racial classifications is more recent. According to psychologist Wade Nobles, the Western idea of race emerged during the sixteenth century as Europeans began to colonize other parts of the world. As they came into contact with people who looked different from them, many Europeans developed the notion that some races were superior to others. This belief often was given as a justification for slavery, imperialism, and other oppressive activities.
Charles Darwin’s theory of evolution was critical in promoting the belief that human differences were a result of heredity and genetics. His notion of the survival of the fittest led psychologists to research racial differences in intelligence to understand the successes and failures of different human groups. Francis Galton, Darwin’s cousin, was instrumental in furthering the hereditarian perspective in psychology. In his book Hereditary Genius: An Inquiry into Its Laws and Consequences (1869), he attempted to illustrate that genius and prominence follow family lines. He also began the eugenics movement, which supported the use of selective mating and forced sterilization to improve racial stock. The Bell Curve is simply a more recent argument along the same lines. Nothing really new is added to the argument. There is a bit more sociobiological jargon and a mass of statistics that do not hold up to careful scrutiny.
Following Galton’s lead, many psychologists embraced the notions of inherited racial differences in intelligence. The pioneering work of anthropologist Franz Boas, in attacking the popular conception of race, fostered research to attack the myths attached to that concept, including the myth of inherent superiority or inferiority. G. Stanley Hall, the founder of the American Psychological Association, believed that African people were at a lower evolutionary stage than whites. By the beginning of the 1900s, psychological testing was being widely used to support the view that intelligence was hereditary and was little influenced by the environment. More recently, Burt, Herrnstein, and Jensen have argued in favor of an overriding genetic factor in intelligence.
There were also early efforts to challenge the hereditarian perspective in psychology. During the 1920s and 1930s, Herman Canady and Howard Long, two of the first African Americans to receive graduate degrees in psychology, produced evidence showing the importance of environmental influences on IQ test performance. They were concerned about increasing scientific justifications for the inequality and injustice experienced by African Americans, Native Americans, and other groups. Fighting racism was a major reason Leon Kamin became involved in the debate about race and intelligence. He gathered the original information that had been reported by scientists and reexamined it; Kamin was responsible for discovering that Burt had reported false information. He also noted that many hereditarians misused and misinterpreted their statistics.
Hereditarians maintain that racial differences in IQ test scores are primarily caused by genetics and that these scores do reflect differences in intelligence; environmentalists say no. It has not been proved definitively that IQ tests measure intelligence; however, the evidence does suggest that performance on IQ tests is determined by the interaction between genetic and environmental influences. The quality of the environment will determine how well people will fulfill their potential. In a society where the history of certain groups includes oppression, discrimination, and exclusion from opportunity, it is difficult to explain differences in achievement as being primarily inherited. Instead, it would seem to be a more important goal to eliminate injustices and to change the conditions of life so that all people could do well.
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