Race and intelligence (interpretations)

Given the observed differences in IQ scores between certain groups, a great deal of debate revolves around the significance of these observations. Some believe that these differences indicate a natural genetic hierarchy of races and suggest that attempts to close the gaps are doomed to fail. Others see the gap as merely reflective of existing socially constructed class hierarchies rather than genetic differences.

Interpretations and public policy


The distribution of IQ scores among individuals of each race overlap substantially. In a random sample of equal numbers of US Blacks and Whites, Jensen estimates most variance in IQ would be unrelated to race or social class. The average IQ difference between two randomly paired people from the U.S. population is approximately 17 points, and this only increases to 20 points when the pair are black and white. When the pair are siblings, the average difference is still 12 points.

In essays accompanying the publication of The Bell Curve, Herrnstein and Murray argue that whether the cause of the IQ gap is genetic or environmental does not really matter, because that knowledge alone would not help to eliminate the gap and that knowledge should not impact the way that individuals treat one another. They argue that group differences in intelligence ought not to be treated as more important or threatening than individual differences, but suggest that one legacy of Black slavery has been to exacerbate race relations such that Blacks and Whites cannot be comfortable with group differences in IQ or any other traits.

Practical importance
The appearance of a large practical importance for intelligence makes some scholars, such as Sackett fear that the source and meaning of the IQ gap is a pressing social concern. In his own words "Sub-group differences in performance on high-stakes tests represent one of American society's most pressing social problems, and mechanisms for reducing or eliminating differences are of enormous interest" and  argue that the IQ gap is reflected by gaps in the academic, economic, and social factors correlated with IQ. However, some dispute the general importance of the role of IQ for real-world outcomes, especially for differences in accumulated wealth and general economic inequality in a nation.

The effects of differences in mean IQ between groups (regardless if the cause is social or biological) are amplified by two statistical characteristics of IQ. First, there seem to be minimum statistical thresholds of IQ for many socially valued outcomes (for example, high school graduation and college admission). Second, because of the shape of the normal distribution, only about 16% of the population scores at least one standard deviation above the mean on IQ tests. Thus, although the IQ distributions for Blacks and Whites are largely overlapping, different IQ thresholds can have a significant impact on the proportion of Blacks and Whites above and below a particular cut-off.

Small differences in IQ, while relatively unimportant at the level of an individual, could theoretically have large effects for the United States population as a whole. As a demonstration of these possible effects, used a resampling technique to argue that, all else equal, a simulated 3-point drop in average IQ had little effect on factors like marriage, divorce, or unemployment. However, their study found that a simulated drop in IQ from 100 to 97-points increased poverty rates by 11% and the proportion of children living in poverty by 13%. In the simulation, similar rises occurred in rates of children born to single mothers, men in jail, high school drop-out, and men prevented from working due to health-related problems. In contrast, when they simulated an increase in average IQ of 3-points to 103, they calculated that poverty rates fell 25%, children living in poverty fell 20%, and high school drop-out rates fell 28%.

Professors James Heckman and Nicholas Lemann, as well as several other scholars and scientists have the criticized validity and reliability of the data which led to the aforementioned findings by.

Controlling for IQ
Because IQ correlates with a number of social and economic outcomes that have been found to differ between the black and white populations overall, The Bell Curve argues that the disparities in outcomes are due to group differences in IQ (See above chart). Professors James Heckman and Nicholas Lemann and others claim that its findings are based on data that is not completely valid and reliable.

According to Murray and Herrnsteins' Bell Curve, when IQ is statistically controlled for, the probability of having a college degree or working in a high-IQ occupation is higher for Blacks than Whites. Controlling for IQ shrinks the income gap from thousands to a few hundred dollars. Controlling for IQ cuts differential poverty by about three-quarters and unemployment differences by half. However, controlling for IQ has little effect on differential marriage rates. For many other factors, controlling for IQ eliminates the differences between Whites and Hispanics, but the Black-White gap remains (albeit smaller).

Another study found that wealth, race and schooling are important to the inheritance of economic status, but IQ is not a major contributor and the genetic transmission of IQ is even less important. Conversely, controlling for IQ in the above studies also reduces the apparent effect of wealth, race and schooling due to this same correlation.

White populations are not homogeneous groups regarding real-world outcomes. For example, in the U.S. 33.6% of persons with self-reported Scottish ancestry completed college, while only 16.7% of persons with self-reported French-Canadian ancestry have done so.

For additional discussion of the effects of controlling for group differences on a variety of outcomes and groups, see, and.

As a result of caste position
This table illustrates how social status or caste position is related to test scores and school success in nations around the world. Source: Inequality by Design: Cracking the Bell Curve Myth by Claude S. Fischer, Michael Hout, Martín Sánchez Jankowski, Samuel R. Lucas, Ann Swidler, and Kim Vos

These results, just like the inferior test scores of Eastern and Southern Europeans immigrants in the United States 75 years ago, may represent a social division that leads to the gaps in test scores, rather than a pre-established and "natural" hierarchy of "races." In other words, these divisions, are closely aligned with local "social constructs" of race, the outcomes for ethnic groups are, in the opinion of these authors, a result of the social structure rather than confirmation of its validity.

White supremacist interpretations
Race and intelligence research is sometimes used by white supremacist organizations to support their theories of white superiority. Like racists in the past, they suggest that the low IQ scores of black people justify segregation and laws against interracial marriage. The Southern Poverty Law Center states that: "Race science has potentially frightening consequences, as is evident not only from the horrors of Nazi Germany, but also from the troubled racial history of the United States. If white supremacist groups had their way, the United States would return to its dark days. In publication after publication, hate groups are using this "science" to legitimize racial hatred.	 In Calling Our Nation, the neo-Nazi Aryan Nations publishes a piece by a New York psychologist surveying the work of Jensen, Garrett and numerous others. National Vanguard, the publication of former physics professor William Pierce and his neo-Nazi National Alliance, runs a similar piece that concludes that "it is the Negro's deficiency ... which kept him in a state of savagery in his African environment and is now undermining the civilization of a racially mixed America."

Louis Andrews through his company L.R. Andrews, Inc. runs Washington Summit Publishers, which reprints a range of classical and modern racist tracts, along with books on eugenics, the discredited "science" of breeding better humans. Andrews has written widely on such matters related to race and intelligence.

Both the FBI and Genocide Watch have observed that the progression towards hate crimes and genocide goes through stages, with the earlier stages necessary for the later. In order for later crimes to occur and often with the help of widespread propaganda, opinions must be formed that people should be categorized into different groups. Certain groups are then degraded and disparaged which by dehumanizing them make active violence possible.

As the cause of economic growth in nations


Some people have attributed differential economic growth between nations to differences in the intelligence of their populations. One example is Richard Lynn's IQ and the Wealth of Nations. The book is sharply criticized in the peer-reviewed paper The Impact of National IQ on Income and Growth. Another peer-reviewed paper, Intelligence, Human Capital, and Economic Growth: An Extreme-Bounds Analysis, finds a strong connection between intelligence and economic growth. It has been argued that East Asian nations underachieve compared to IQ scores.

Jared Diamond's Guns, Germs and Steel instead argues that historical differences in economic and technological development for different areas can be explained by differences in geography (which affects factors like population density and spread of new technology) and differences in available crops and domesticatable animals. However, these environmental differences may operate in part by selecting for higher levels of IQ