In the 17th century, Western philosophers began arguing over the relative role of "nature" or "nurture" in the shaping of human capacities and predilictions. By the 19th century, most Westerners agreed that this was a question that could only be resolved through scientific research. By the beginning of the 20th century, however, natural, behavioral, and social scientists began questioning not only the relationship between nature, nurture, and human behavior -- they began debating the scientific validity of these concepts as commonly understood.

Today virtually all scientists agree that no single characteristic, trait or even gene (i.e. haplotype) distinguishes all the members of one race from all the members of another race. Many continue to use "race" as a biologically meaningful and useful term, but emphasize that genetic similarities within races are mutable, and recognize that many traits have both genetic and environmental determinants; most, however, have rejected the concept "race" as a biological category (seeing it instead as a cultural category), and speak instead of "populations;" (see Race). Because of a population bottle neck, humans are relatively very similar at the level of genotype. Some would argue that this genetic similarity disproves the existence of races. Consistent with that hypothesis, most of the total genetic variation can be found within, not between races. Nevertheless, population geneticists have studied patterns in the distribution various genes, and the functional importance of human genetic variation. Most scientists agree that genetically distinguishable populations have developed during the last 50,000 years with episodes of genetic mixture between groups throughout. At least some of the phenotypic differences between populations (e.g. skin color) seem to have functional importance (e.g. adaptation to climate). Moreover, the distribution of such differences follows a continuum (i.e., the closer one's ancestors lived to the equator, the darker one's skin; the further away from the equator, the lighter).

Most scientists could agree that humans are distinguished by a capacity for symbolic thought, and that this capacity has a physical basis in the human brain. There is considerable debate over whether this capacity corresponds with what psychologists call g, which is measured by I.Q. tests (see Intelligence). Furthermore, there is considerable debate over the extent to which differences in I.Q. among humans, and groups of humans, is a result of genetic or environmental factors (see also nature versus nurture.)

The research on the relationship between intelligence, heredity and ethnic groups has been evaluated and interpreted in various ways. According to many writers, most race-based claims about intelligence were not derived from the results of truly value-free scientific testing, but rather from testing biased by racial prejudice. 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.

Table of contents
1 IQ Gap Among Races
2 Early Intelligence tests in America
3 Methodologicial and conceptual problems
4 Criticisms of "The Bell Curve"
5 External links

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 comparisons were made 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.

The performance differences persist in tests and testing situations that are not biased. There is currently no evidence that the mean IQ of ethic/racial groups is converging. The gaps are slightly smaller but still persist for individuals from the same socioeconomic backgrounds.

The source of the gaps in IQ scores is not truly known. 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.

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 test 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 races. It is difficult to imagine that people could be motivated during one part of the test but not motivated during the other.

Arthur Jensen is a proponent of the hereditarian view of intelligence and seems to support the hypothesis that the IQ gap is in part genetic.

Early Intelligence tests in America

In early U.S. IQ testing, Americans of black African descent, Jews, and other recent immigrants from Europe, were assigned scores that were significantly lower on average (mean of 85) than "white" people (mean of 100), with "Hispanics" somewhere in between. Some researchers seized upon these early results as evidence for the hypothesis that race determines intelligence. This hypothesis was much later rejected by some as badly flawed for a number of reasons, notably because they did not consider the relationship between IQ and any other factor.

Current research has found a strong correlation between IQ test scores and such factors as education level and family income. For modern researchers, the earlier failure to control or correct for these factors made the earlier studies scientifically useless.

However, race remains a powerful social idea in Western societies. It provides people different access to opportunities and resources. Government and social institutions -- especially in the Americas -- have created advantages that disproportionately channel wealth, power, and resources to white people. This affects everyone, whether they are aware of it or not.

Methodologicial and conceptual problems

Later studies on race and IQ have attempted to make corrections for the earlier lack of controls. Some of these studies show that a measurable IQ gap between people of different races does exist, and is only slightly smaller than previously reported. Many of these studies show no significant IQ gap between "white", "Jewish" and "Asian" people, but they do show a significant IQ gap between these groups and black African Americans. These studies have received a skeptical reception in the scientific community, partly because of methodological problems.

Many people are skeptical of modern tests, and give as a reason the early 20th century studies which showed large IQ deficits in Irish and southern European immigrants to the United States. However, the IQ of people in these groups today is now seen to be the same as that in other groups considered "white".

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 were once 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 the conclusions were valid.

Since then, many other scientists have disputed the evidence presented 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. One 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).

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. Third, even as far as genetics is involved, 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.

His 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.

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.

Anthropologists have argued that intelligence is a cultural category; some cultures emphasize speed and competition more than others, for example. Tests based on word skills cannot accurately measure learning ability. And most IQ tests ask people to solve problems most often encountered in middle class settings. Low IQ scores are often the result of the subject speaking a different language or dialect than the test questions, or being given the test by someone from another ethnic group, or simply being tired, malnourished, or ill. IQ tests do not measure mental ability, they do measure enculturation. During WWI African-Americans from the north tested higher than those from the south. This is simply because African-Americans in the north had received more formal education (see Race: Science and Politics, written by Ruth Benedict in 1940). Thousands of ethnographic studies indicate that innate capacities for cultural evolution are equal among all human populations. See the American Anthropological Association's Statement on Race and Intelligence [[1]

Assuming that this gap in IQ (and SAT scores) is real, even when corrected for social and financial differences, it is not clear what the origins of this gap are. Part of this gap may well be genetic; there is no a priori reason to believe that every ethnic group or race has precisely the same genes in all areas of neural development; a small amount of random variation early on may have later crystallized into such differences at later times. Also there might have been smaller evolutionary pressure towards greater intelligence in some environments. However, the possibility that any differences are genetic do not explain why minorities in some societies show similar deficits in IQ even where they are genetically identical to the majority population (such as Catholics in Northern Ireland, or Burakumin in Japan).

Scientists have firmly established that most genetic variations in individuals are only a part of the picture of how an individual develops. The environment that a person is brought up in is equally important. Further, there are painful social factors involved, such as the high rate of drinking, smoking, and illicit drug use during pregnancy of inner-city teenagers. These activities are known to cause measurable mental damage to children born to parents engaging in such activities. Thus, as cities and states work to reduce the amount of smoking, alcoholism and illicit drug use, this may significantly reduce much or all of the IQ and SAT score gaps that are currently being measured. In this case, the gap would be a symptom of a wider social problem, and not a statement about race at all.

In recent years there have been a few theories as to why Ashkenazi Jews have higher intelligence scores on standardized tests and more economic and professional success in society than people in many other ethnic groups. One theory by Gregory Cochran, based on studies of genetic disease of the brain peculiar to Ashkenazi Jews, proposes that recessive forms of certain mutations have an adaptive function that results in higher intelligence. A discussion and critique of this theory is presented on the following page:

Overclocking: A theory on genetic disease, intelligence and Ashkenazi Jews

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 may provide a resolution of the contradiction between the viewpoint of The Bell Curve's authors and the 'nurture' effects observed by others.

See also:

External links