Race and intelligence
During the 17th century, Western
philosophers began arguing over the
relative role of "nature" or "nurture in shaping human capacities and tendencies. By the 19th century, most of the Western world had come to the view that this was a question that would best be resolved by "science," though the common science of the 19th century was still in its infancy, and hence could operate under extreme fallacies by today's standards.
It is in the context of this scientific and cultural development that the concepts originally defined by the question of "nature versus nurture" have changed to reflect the rejection of the
prejudicial and
idiomatic use of the terms "race" and "intelligence," for use in science. As science would continually re-evaluate its use of the
terms, (and hence, redefine the operational concepts by which it formulated its inquiries), so too would the common culture gain insight from the debate within the scientific world.
Background
Researchers have recognized and studied many aspects that are associated with race and intelligence. The development of scientific classification taxonomy has largely moved away from use of the term "race" as a scientific definition. Many scientists have rejected use of the word "race" as it appears in common parlance. They do so on the grounds that the actual genetic makeup of human beings does not support a single privileged way to separate humans into discrete subsets (such as subspecies). In other words, some systems of racial categorization would group two specific individuals into the same race, while other systems would place the same two individuals into different races, and there is no biological or genetic reason to prefer one system over the other. They argue that the choice of categorization systems is determined largely by non-biological factors and is therefore an artifact, i.e., a "social construct." A complete analysis is lacking because the words are applied to many different-but-related concepts.
Today scientists agree that no single characteristic, trait or gene (i.e., haplotype) distinguishes all the members of one race from all the members of another race. Because of our recent evolution, humans are relatively very similar at the level of genotype. That view is also supported by the fact that most of the total genetic variation can be found within, not between, the putative races. However, most scientists agree that genetically distinguishable populations have developed during the last 50,000 years, with episodes of genetic mixture between groups throughout. Population geneticists have studied patterns in the distribution of various genes and the functional importance of human genetic variation. This divergence has long been recognized to have affected the distribution of alleles for traits such as skin pigmentation and the epicanthic fold of Asians. However, the genetic divergence has affected traits that are more than skin deep. In biomedical research, it has been recognized that self-reported race is a significant predictor of disease susceptibility and prognosis. Diseases like sickle-cell anemia that disproportionately afflict members of one race demonstrate the utility of race in enabling physicians to better decide which disease factors to rule out first when diagnosing a patient. It is possible, but not proven, that functionally significant differences in the distribution of cognitive traits have emerged between races. For the purpose of economy of expression, this article will use the word "race" as a substitute for the scientifically more precise term "population" and not as an equivalent to "subspecies".
Humans are distinguished from other animals by their great capacity for symbolic thought, abstract thinking, problem solving, and ability to learn new concepts. Most scientists and many psychologists collectively refer to these abilities as intelligence, and more specifically as g. They attempt to measure intelligence with IQ tests. This article discusses the relationship between race (or human populations) and the distribution of intelligence.
Debates
This area is an active area of research, and a number of debates exist within the field. There are debates on
- whether it is reasonable to evaluate this multitude of mental abilities in a single measurement (i.e. one's IQ).
- whether the results of IQ tests are culturally biased or not.
- the extent to which differences in IQ among humans, and groups of humans, are a result of genetic or environmental factors and how early environmental and genetic factors interact to influence brain structure. (See also nature versus nurture.)
The research on the relationship between intelligence, heredity, and ethnic groups has been interpreted in various ways. According to many writers, most race-based claims about intelligence were not derived from the results of value-free scientific testing, but rather from testing biased by racial prejudice or unconscious assumptions about what stands as common knowledge. As such, this is an example of a larger debate over the possibilities of value-free science, and the relationship between knowledge and culture. In countries where racism is a national-level issue, the topic -- while controversial -- has remained an issue that is discussed within mainstream society.
IQ gap among races
The modern controversy surrounding intelligence and race focuses on the results of IQ studies conducted during the second half of the 20th century in the United States, Western Europe, and other industrialized nations. In almost every testing situation where the tests were administered and evaluated correctly, a difference of approximately one standard deviation was observed between the mean IQ score of blacks and whites. That is, the mean IQ score among blacks is approximately 85 and the mean IQ score among whites is approximately 100. In the United States, the mean IQ score of Hispanics is usually reported to be intermediate to the mean black and white scores. The mean score for people of East Asian and Jewish descent is usually higher than the mean score of whites, but the extent of that difference is not precisely known. However, most studies place the median IQ of Ashkenazi Jews (who make up the overwhelming majority of American Jews) at approximately one standard deviation above the mean for other whites. Note that in a normal distribution, only about 16% of the population is at least one standard deviation above the mean.
Similar gaps are seen in other tests of cognitive ability or aptitude, including the SAT. Likewise, the gap is reflected by gaps in the academic, economic, and social factors correlated with IQ. The practical importance of intelligence makes the source and meaning of the IQ gap a pressing social concern.
Interpreting group differences
There is currently no evidence that the mean IQ of ethnic/racial groups is converging. The source of and meaning of the IQ gap is not known. Many theories have been proposed, but none are generally accepted. Most of the theories are supported by only indirect evidence. The cause may be environmental. Many attribute the difference primarily to cultural factors that disadvantage caste-like minorities. The size of the black-white IQ gap is one standard deviation. The Flynn effect is a known example of an environmental effect that can alter IQ scores by at least that much. Likewise, genetic factors could also be responsible. Many researchers in the field of intelligence suggest that the difference is partially genetic and partially environmental. Other observers insist that the differences may be entirely environmental. The cause of the IQ gap may be identical to the cause of IQ differences between all individuals, or it may represent a race-specific effect. This is an active area of research.
Unfair/biased test
It has been suggested that IQ tests may be biased against minorities, and that this accounts for part or whole of the IQ gap. Currently there is not evidence for test bias. IQ tests are equally good predictors of IQ-related factors (such as school performance) for blacks as whites. The performance differences persist in tests and testing situations in which care has been taken to try to eliminate all forms of bias. It has also been suggested that IQ tests are formulated in such as way as to disadvantage minorities. Controlled studies have shown that this does not substantially contribute to the IQ gap. Moreover, attempts to create better tests that minimize any disadvantage have failed.
Socio-economic factors
IQ is correlated with economic factors. Blacks and Hispanics suffer poorer economic conditions than whites. It has been suggested that the effects of poverty are responsible for some or all of the IQ gap. However, economics cannot be the whole explanation. First, the gaps are slightly smaller but still persist for individuals from the same socioeconomic backgrounds. Second, except for extreme environments, factors associated with poverty account for little of the variance in IQ scores. Third, it is believed that IQ determines income, and not the other way around.
Other researchers have come across what they see as additional reasons for the IQ gap. The paper Poverty and Brain Development in Early Childhood holds that there is a large amount of neural damage in many American black and Hispanic children due to inadequate nutrition, substance abuse of the children's parents, a high incidence of maternal depression, exposure to environmental toxins, psychological trauma, and the neural effects of physical abuse.
Researchers have found that many American blacks and Hispanics are not given sufficient opportunity to learn language and thinking skills during the first three years of life, possibly due to economic status. The first three years are especially critical years for neural development of the brain, and previous studies have shown that when human children were deprived of most or all language skills at an early age, they never developed the ability to master language at a later age; if they only mastered a small amount of language and thinking skills at a young age, then they could only make small improvements in later years. A recent study has shown that many American blacks and Hispanics are raised in homes where their parents speak relatively few sentences, and the sentences usually show only simple grammar. As a result, their children never hear millions of words during the time when their brains are developing linguistic skills. Without this linguistic input during their developing years, many are observed to quickly fall behind, and they can never catch up. Children in poorer welfare families, which includes a higher percentage of many minority populations, apparently hear up to 30 million fewer words by age three than children in higher income, usually white, families. (Source: The Early Catastrophe: The 30 Million Word Gap by Age 3)
Caste-like minorities
Like blacks and Hispanics in the US, minorities in some societies show achievement gaps (such as the Maori in New Zealand, scheduled castes ("untouchables") in India, non-European Jews in Israel, and the Burakumin in Japan). Whether caste membership is a cause of low IQ scores has not been empirically established.
Minority culture
It has been suggested that black culture disfavors academic achievement and fosters an environment that is damaging to IQ. Likewise, it is argued that a persistence of racism reinforces this negative effect.
One environmental source of the IQ gap which has been suggested is poor motivation among low scorers. This hypothesis is seemingly discredited by findings promoted by the researcher Arthur Jensen using elementary cognitive tasks to measure intelligence. For example, one such test asks the subject to lift a finger from a depressed button to strike a light when it flashes. When more than one light is offered as a target the task involves a decision of which to hit (i.e. the one which is lit). These tests measure both reaction time (from when the bulb illuminates to when the subject lifts their finger) and movement time (from when the subject lifts their finger to when the subject reaches the bulb). While movement time measurements show no difference (or an advantage to blacks), reaction time measurements negatively correlate with IQ scores and show the same performance gaps between those two races. Jensen argues that it is difficult to imagine that people could be motivated during one part of each segment of the test but not motivated during the other.
Cultural explanations for the IQ deficit among blacks and Hispanics compared to whites and Asian minorities are complemented – and sometimes challenged – by the observation that Asian minorities score well on IQ tests and on average enjoy greater economic success than other minorities. Likewise, Jewish populations have suffered past discrimination and persecution, but do not exhibit an IQ deficit.
The genetic hypothesis
Part of the gap may well be genetic; there is no a priori reason to believe that every ethnic group or race has precisely the same distribution of genes that affect intelligence; a small amount of random variation early in human evolution may have later crystallized into differences seen today. Also there might have been smaller evolutionary pressure towards greater intelligence in some environments.
Comparative economic analyses are sometimes presented as evidence that environmental explanations of the IQ gap are incomplete. IQ and the Wealth of Nations, a book by Richard Lynn and Tatu Vanhanen, is the most recent prominent example of an economic analysis of the IQ and race issue.
Arthur Jensen is a proponent of the hereditarian view of intelligence and seems to endorse the hypothesis that the IQ gap is at least partly genetic. In this view, average intelligence differences among races are like average skin color differences: a product of different allelic frequencies within each population.
The genetic hypothesis is often ignored or disregarded in primary research. However, it has been well studied by researchers doing meta-analyses that combine multiple sources of primary materials. Some argue that the preponderance of the evidence favors the genetic hypothesis for reasons of parsimony (see Occam's Razor). They cite the persistance and stability of the IQ gap across time and geography as evidence that favors a genetic contribution to racial IQ differences. Because the cause of the IQ gap is ultimately an empirical question, it should be possible to resolve this question in the future. Irrefutable direct evidence is currently lacking.
Other explanations
A recent paper in the Psychological Review, "Heritability Estimates Versus Large Environmental Effects: The IQ Paradox Resolved" by William T. Dickens of The Brookings Institution and James R. Flynn presents a mechanism by which environmental effects on IQ may be magnified by feedback effects. This work may provide a resolution of the contradiction between the viewpoint of The Bell Curve's authors and the 'nurture' effects observed by others.
Gould's criticisms of "The Bell Curve"
Much of the controversial research has been summarized in great detail in The Bell Curve, published in 1994 by Richard J. Herrnstein and Charles Murray. It immediately attracted much media attention, and was denounced by some as thinly veiled racism. The authors have repeatedly been publicly denounced as racists. In response to the debate, a public statement circulated by fifty two internationally known scholars was published in The Wall Street Journal, (December 3, 1994), which summarized what they considered to be the mainstream views on race and IQ. These scholars held that the reasoning and data in the book were reliable, and that most of the conclusions were valid.
Since then, many other scientists have disputed the analysis in The Bell Curve, and have found what they see as serious methodological flaws. A critique of the book can be found in the revised and expanded edition of The Mismeasure of Man, by Stephen Jay Gould (1996, W. W. Norton and Co., ISBN 0393039722.)
In the first edition of that book, published in 1981, Gould made a number of critical points concerning many of the studies Herrnstein and Murray were to draw on. Gould's larger point is that most scientific studies of the relationship between race and human behavior have been heavily biased by the assumption that human behavior is best explained by heredity. He criticizes studies of the relationship between race and intelligence on several grounds. \nOne thing he points out is that much of the data that earlier scientists relied on may have been falsified. The prime example is Cyril Burt's famous study of the IQs of twins separated at birth. Serious questions have been raised as to the actual extent of Burt's research (but recent studies have yielded reliable estimates of the heritability of intelligence, which fall within the same quantitative range as Burt's figures - and it should also be noted that the specific charges against Burt by Leon Kamin about "invariant correlations" have since been shown to be seriously flawed).
Most of Gould's criticisms pertain to cases where the data seems to be legitimate. Most of his arguments have to do with the value of statistical correlations (the measure of the co-occurrence of two different things). Most arguments around IQ center on the issue of correlation -- the claim that the test measures an actual thing requires that the answers to various questions will correlate highly; the claim that this thing is inherited requires that the scores of respondents who are closely related will correlate significantly more highly than results of those distantly related.
First, he points out that correlation is not the same as cause. As he puts it, measures of the changes, over time, in "my age, the population of Mexico, the price of Swiss cheese, my pet turtle's weight, and the average distance between galaxies" will have a high positive correlation -- but that does not mean that Steven Jay Gould's age goes up "because" the population of Mexico goes up. Second, and more specifically, a high positive correlation between parents' IQ and children's IQ can be taken as evidence that IQ is inherited -- OR that IQ is determined by social and environmental factors. Since the same data can be used to argue either side of the case, the data in and of itself is not useful. This is why studies of twins separated at birth, and of adopted children, are given so much attention.
Furthermore, Gould makes the subtle and often ignored point that even if it were demonstrated that the correlations in IQ within a group were completely determined by heredity, this tells you nothing about the causes in differences in IQ between unrelated groups or whether those differences can be changed by environment. One example that Gould brings up is height which is known to be highly heritable. Knowing that differences in height within a single group are due to heredity tells you nothing at all about why there are height differences between different groups.
According to Gould, a good example of the confusion of heritability is found in the statement of international scholars published in the Wall Street Journal (see web-link above): "If all environments were to become equal for everyone, heritability would rise to 100% because all remaining differences in IQ would necessarily be genetic in origin.". He says that this claim is at best misleading and at worst, false. First, it is very hard to conceive of a world in which everyone grows up in the exact same environment; the very fact that people are spatially and temporally dispersed means that no one can be in exactly the same environment (a simple example will illustrate how complex social environments are: a husband and wife may share a house, but they do not live in identical environments because each is married to a different person). Second, even if people grew up in exactly the same environment, not all differences would be genetic in origin. This is because embryonic development involves chance molecular events and random cellular movements that alter the effects of genes.
Gould argues that heritability is not a measure of phenotypic differences between groups, but rather differences between genotype and phenotype within a population. Even within a group, if all members of the group grow up in exactly the same environment, it does not mean that heritability is 100%. All Americans (or New Yorkers, or upper-class New Yorkers -- one may define the population in question as narrowly as one likes) may eat exactly the same food, but their adult height will still be a result of both genetics and nutrition. In short, heritability is almost never 100%, and heritability tells us nothing about genetic differences between groups. This is true for height, which has a high degree of heritability; it is all the more true for intelligence. This is true for other reasons besides ones involving "heritability," as Gould goes on to discuss.
Gould's most profound criticism is his rejection of the very thing that IQ is meant to measure, "general intelligence" (or "g"). IQ tests, he points out, ask many different kinds of questions. Responses to different kinds of questions tend to form clusters. In other words, different kinds of questions can be given different scores -- which suggests that an IQ test is really a combination of a number of different tests that test a number of different things. Proponents of IQ tests assume that there is such a thing as general intelligence, and analyze the data so as to produce one number, which they then claim is a measure of general intelligence. Gould argues that this one number (and therefore, the implication that there is a real thing called "general intelligence" that this number measures) is in fact an artifact of the statistical operations psychologists apply to the raw data. He argues that one can analyze the same data more effectively and end up with a number of different scores (but valid, meaning they measure something) rather than one score.
Finally, Gould points out that he is not opposed to the notion of "biological variability" which is the premise that heredity influences intelligence. He does criticize the notion of "biological determinism" which is the idea that genes determine destiny and there is nothing we can or should do about this. Many people who study race intelligence hold that Gould is not representing their views correctly, and is effectively engaging in straw-man attacks on their work.
The book The Bell Curve Debate: History, Documents, Opinions, edited by Russell Jacoby and Naomi Glauberman, offers a range of responses to the book and these issues.
See also
\n* Race\n* Flynn effect\n* Stanley Porteus
External links
\n* Wall Street Journal: Mainstream Science on Intelligence\n* American Psychological Association 1996 statement on race and intelligence\n* Legal scholar and microbiologist Pilar Ossorio answers questions from viewers about science, medicine, racial classification, and more.\n* Prof. Evelynn Hammonds on the history of race in science and medicine in the United States\n* "Heritability Estimates Versus Large Environmental Effects: The IQ Paradox Resolved"; Psychological Review, 2001, Vol. 108, No. 2, 346–369\n* "We're All Related To Kevin Bacon" -- Steve Olson on popular misconceptions about genetics in the Washington Post \n* The Skeptic's Dictionary entry on IQ and race\n* Poverty and Brain Development in Early Childhood 1999 report\n* The Early Catastrophe: The 30 Million Word Gap by Age, American Educator, Spring 2003
