Ethnic Similarities and Differences
Fueling the group-differences debate are two other disturbing but agreed-upon facts:
- Racial groups differ in their average intelligence test scores.
- High - scoring people (and groups) are more likely to attain high levels of education and income.
A statement by 52 intelligence researchers explained: “The bell curve for Whites is centered roughly around IQ 100; the bell curve for American Blacks roughly around 85; and those for different subgroups of Hispanics roughly midway between those for Whites and Blacks” (Avery et al., 1994). Comparable results come from other academic aptitude tests. In recent years, the Black-White difference has diminished somewhat, and among children has dropped to 10 points in some studies (Dickens & Flynn, 2006). Yet the test score gap stubbornly persists, and other studies suggest the gap stopped narrowing among those born after 1970 (Murray, 2006, 2007). There are differences among other groups as well. New Zealanders of European descent outscore native Maori New Zealanders. Israeli Jews outscore Israeli Arabs. Most Japanese outscore the stigmatized Japanese minority, the Burakumin. And those who can hear outscore those born deaf (Braden, 1994; Steele, 1990; Zeidner, 1990). Everyone further agrees that such group differences provide little basis for judging individuals. Women outlive men by six years, but knowing someone’s sex doesn’t tell us with any precision how long that person will live. Even Charles Murray and Richard Herrnstein (1994), whose writings drew attention to Black-White differences, reminded us that “millions of Blacks have higher IQs than the average White.” Swedes and Bantus differ in complexion and language. That first factor is genetic, the second environmental. So what about intelligence scores?
As we have seen, heredity contributes to individual differences in intelligence. Does that mean it also contributes to group differences? Some psychologists believe it does, perhaps because of the world’s differing climates and survival challenges (Herrnstein & Murray, 1994; Lynn, 1991, 2001; Rushton & Jensen, 2005, 2006). But we have also seen that group differences in a heritable trait may be entirely environmental, as in our earlier barrel-versus-home–reared boys example. Consider one of nature’s experiments: Allow some children to grow up hearing their culture’s dominant language, while others, born deaf, do not. Then give both groups an intelligence test rooted in the dominant language, and (no surprise) those with expertise in that language will score highest. Although individual performance differences may be substantially genetic, the group difference is not (FIGURE 10.15).
Also consider: If each identical twin were exactly as tall as his or her co-twin, heritability would be 100 percent. Imagine that we then separated some young twins and gave only half of them a nutritious diet, and that the well-nourished twins all grew to be exactly 3 inches taller than their counterparts—an environmental effect comparable to that actually observed in both Britain and America, where adolescents are several inches taller than their counterparts were a half-century ago. What would the heritability of height now be for our well-nourished twins? Still 100 percent, because the variation in height within the group would remain entirely predictable from the heights of their malnourished identical siblings. So even perfect heritability within groups would not eliminate the possibility of a strong environmental impact on the group differences.
Might the racial gap be similarly environmental? Consider:
Genetics research reveals that under the skin, the races are remarkably alike (Cavalli-Sforza et al., 1994; Lewontin, 1982). Individual differences within a race are much greater than differences between races. The average genetic difference between two Icelandic villagers or between two Kenyans greatly exceeds the group difference between Icelanders and Kenyans. Moreover, looks can deceive. Light-skinned Europeans and dark-skinned Africans are genetically closer than are dark-skinned Africans and dark-skinned Aboriginal Australians.
Race is not a neatly defined biological category. Some scholars argue that there is a reality to race, noting that there are genetic markers for race (the continent of one’s ancestry) and that medical risks
(such as skin cancer or high blood pressure) vary by race. Behavioral traits may also vary by race. “No runner of Asian or European descent—a majority of the world’s population—has broken 10 seconds
in the 100-meter dash, but dozens of runners of West African descent have done so,” observes psychologist David Rowe (2005).
Many social scientists, though, see race primarily as a social construction without well-defined physical boundaries (Helms et al., 2005; Smedley & Smedley, 2005; Sternberg et al., 2005). People with varying ancestry may categorize themselves in the same race. Moreover, with increasingly mixed ancestries, more and more people defy neat racial categorization. (What race is Tiger Woods?) Asian students outperform North American students on math achievement and aptitude tests. But this difference appears to be a recent phenomenon and may reflect conscientiousness more than competence. Asian students also attend school 30 percent more days per year and spend much more time in and out of school studying math (Geary et al., 1996; Larson & Verma, 1999; Stevenson, 1992). The intelligence test performance of today’s better-fed, better-educated, and more test prepared population exceeds that of the 1930s population—by the same margin that the intelligence test score of the average White today exceeds that of the average Black. No one attributes the generational group difference to genetics. White and Black infants have scored equally well on an infant intelligence measure
(preference for looking at novel stimuli—a crude predictor of future intelligence scores [Fagan, 1992]).
When Blacks and Whites have or receive the same pertinent knowledge, they exhibit similar information-processing skill. “The data support the view that cultural differences in the provision of information may account for racial differences in IQ,” report researchers Joseph Fagan and Cynthia Holland (2007). In different eras, different ethnic groups have experienced golden ages—periods of remarkable achievement. Twenty-five-hundred years ago, it was the Greeks and the Egyptians, then the Romans; in the eighth and ninth centuries, genius seemed to reside in the Arab world; 500 years ago it was the Aztec Indians and the peoples of Northern Europe. Today, people marvel at Asians’ technological genius. Cultures rise and fall over centuries; genes do not. That fact makes it difficult to attribute a natural superiority to any race.
Moreover, consider the striking results of a national study that looked back over the mental test performances of White and Black young adults after graduation from college. From eighth grade through the early high school years, the average aptitude score of the White students increased, while those of the Black students decreased—creating a gap that reached its widest point at about the time that high school students take college admissions tests. But during college, the Black students’ scores increased “more than four times as much” as those of their White counterparts, thus greatly decreasing the aptitude gap. “It is not surprising,” concluded researcher Joel Myerson and his colleagues (1998), “that as Black and White students complete more grades in high school environments that differ in quality, the gap in cognitive test scores widens. At the college level, however, where Black and White students are exposed to educational environments of comparable quality . . . many Blacks are able to make remarkable gains, closing the gap in test scores.”
Source: Psychology 9th Edition by David Myers Chapter 10. Intelligence p. 434
