Read The Bell Curve: Intelligence and Class Structure in American Life Online
Authors: Richard J. Herrnstein,Charles A. Murray
Tags: #History, #Science, #General, #Psychology, #Sociology, #Genetics & Genomics, #Life Sciences, #Social Science, #Educational Psychology, #Intelligence Levels - United States, #Nature and Nurture, #United States, #Education, #Political Science, #Intelligence Levels - Social Aspects - United States, #Intellect, #Intelligence Levels
The Bell Curve: Intelligence and Class Structure in American Life (60 page)
Regression to the Mean to the Rescue?
Those who dismiss the importance of dysgenic trends have mistakenly latched onto the statistical phenomenon known as regression to the mean as a magic cure-all. The editorial page of the
New York Times,
no less, is on record with an assurance to its readers that because of regression to the mean, each successive generation of children of below-average IQ women will get closer to the average and therefore black and white scores will tend to converge.
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Alas, it doesn’t work that way. The results on the PPVT provide a concrete illustration.Suppose that we recalculate the gap between the three ethnic groups in two successive generations, this time expressing them in terms of standard deviations based on the mothers’ and childrens’ own standard deviations, not on their place within the national distribution (as in the preceding table).
Regression to the Mean and Ethnic Differences in Test Scores in Two Generations Ethnie Comparison Gap Separating the Mothers in SDs Gap Separating the Children in SDs White-black 1.17 1.17 White-Latino 1.05 .93 Calculated in this way and shown in the table above, the gap between white and Latino children has shrunk somewhat compared to the gap separating their mothers. The gap between white and black children has at least grown no larger.
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Why can we obtain this result and still show a growing gap in IQ points between the ethnic groups? The answer is that “mean” referred to in “regression to the mean” is
the population’s own mean.
White children of dull white women will, on average, be closer to the mean for whites in
their
generation than their mothers were in
their
generation. A parallel statement applies to black children of dull black women. But this does not necessarily imply that the IQ scores of black and white children must be closer to each other than their mothers’ IQ scores were. It is a slippery concept. Some people find it is helpful to remember that regression to the mean works both ways: If you start with a population of dull children and then find the IQs of their parents, you will find that the parents were closer to the mean (on average) than their children. Regression to the mean is a statistical phenomenon, not a biological one.
Recently the debate over immigration has intensified, as the large influx of immigrants in the 1980s, legal and illegal, has reopened all the old arguments. Those who favor open immigration policies point to the adaptability of earlier immigrant populations and their contribution to America’s greatness, and remind us that the dire warnings of earlier antiimmigrationists were usually unfounded.
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Anti-immigrationists instead emphasize the concentration within some immigrant groups of people who commit crimes, fail to work, drop out of school, and go on public assistance. They see limits in the American capacity for assimilating people from alien cultures and for finding productive work for them.
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It seems apparent that there are costs and benefits to any immigration policy and that no extreme view, pro or con, is likely to be correct. Beyond that truism, it is apparent that the normative “American” will undergo at least as large a change in the twenty-first century as he has since the original settlement. The nearly 100 percent of immigrants from northern and western Europe in the original settlement gave way to increasing fractions from Africa and from southern and eastern Europe throughout the nineteenth century, thence to a large majority from Asia and Latin America today. America was remade several times over by its immigrants before, and we trust the process will continue. By 2080, according to a typical estimate, America’s population will be less than 50 percent non-Latino white, 15 percent black, 25 percent Latino, and over 10 percent Asian and other.
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Multiculturalism of some sort is certain. Whether it will be a functioning multiculturalism or an unraveling one is the main question about immigration, and not one we can answer.
Our first objective is simply to bring to people’s attention that the question is important. Legal immigration in the 1980s contributed 29 percent of the United States’ net population increase, much more than at any earlier period in the postwar era.
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If illegal immigration could be included, the figure would be significantly higher. Immigration does indeed make a difference to the future of the national distribution of intelligence. It may not make as much difference as births in terms of raw numbers, but there is also this consideration: Whereas policy can have only long-term effects on the cognitive distribution of births, it can have large immediate effects on the nature of the immigrant population.
There are few, if any, other domains where public policy could so directly mold the cognitive shape of things to come. Meanwhile, the nation’s political ground rules have yet to accept that the intelligence of immigrants is a legitimate topic for policymakers to think about.
In trying to estimate an envelope of what the effects on the cognitive distribution might be, a useful first step is to assume that immigrants to the United States have the mean IQ that has generally been found among persons of that ethnic group, then apply those numbers to the actual distribution of immigrants by ethnicity. Keeping in mind that we are hoping to do no more than establish a range of possibilities, we will begin by following Richard Lynn’s computations based on a review of the international data and assign means of 105 to East Asians, 91 to Pacific populations, 84 to blacks, and 100 to whites.
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We assign 91 to Latinos. We know of no data for Middle East or South Asian populations that permit even a rough estimate. They and an unclassifiable “other” component in the immigration statistics constitute about 11 percent of immigrants and are omitted from the analysis. The ethnic ancestry of legal immigrants in the 1980s breaks down as follows:
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| Latino | 41% |
| East and Southeast Asian | 21% |
| Non-Latino white | 11% |
| Black | 9% |
| Filipino | 7% |
| Middle East, South Asian, other | 11% |
Applying the assigned IQ means to this breakdown, the mean IQ of immigrants in the 1980s works out to about 95—essentially unchanged from the 1960s and the 1970s (when the same procedure yields estimates of 96 and 95 respectively). As the proportion of non-Latino whites dropped from 46 percent of immigrants in the 1960s to 11 percent in the 1990s, the percentage of East and Southeast Asians rose from 6 percent to 21 percent, two counterbalancing trends regarding IQ.
Modifying the estimates of ethnic IQs does not make much difference. Some would argue that the East Asian mean is too high. Suppose we drop it to 100. Some would argue that the Latino mean is too low. Suppose we increase it to 94. We could shift the black estimate up or
down by large amounts without affecting the overall mean very far. Fiddling with the numbers moves the overall estimated mean by only about a point or two for defensible sets of values. The basic statement is that about 57 percent of legal immigrants in the 1980s came from ethnic groups that have scores significantly below the white average, and in consequence the IQ mean for all immigrants is likely to be below 100.
How about the idea that people who are willing to pack up and move to a strange place in search of a better life are self-selected for desirable qualities such as initiative, determination, energy, and perhaps intelligence as well? Given this plausible expectation, why not assume that the mean for immigrants is significantly
higher
than average for their ethnic groups? Here, the NLSY provides a snapshot of the effects on the distribution of intelligence of the people coming across our borders, insofar as we may compare the IQs of those who were born abroad with those who were born in the United States.
Overall, the IQ of NLSY members who were born abroad was .4 standard deviation lower than the mean of those who were born in the United States, putting the average immigrant for this cohort at about the 34th centile of the native-born population. A breakdown of these results by ethnic groups reveals that different groups are making different contributions to this result. White immigrants have scores that put them a bit above the mean for the native-born American population (though somewhat lower than the mean for native-born American whites). Foreign-born blacks score about five IQ points higher than native-born blacks, for reasons we do not know. Latino immigrants have mean scores more than seven points lower than native-born Latinos and more than a standard deviation below the overall national native-born mean. The NLSY gives no information on the large immigrant population from the countries of East Asia and Vietnam, who might be significantly boosting the immigrant mean.
Even considered simply as cognitive test scores, these results must be interpreted very cautiously. Immigrants typically earn higher scores on tests as they become acculturated, even on tests designed to be “culture fair.”
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The extremely large gap between native-born and foreign-born Latino students seems likely to reflect additional effects of poor English. We do not know if this rise with acculturation is enough to counter-balance the overall .4 standard deviation disadvantage of a sample born elsewhere. Nonetheless, keeping all of these qualifications in mind, the kernel of evidence that must also be acknowledged is that Latino and
black immigrants are, at least in the short run, putting some downward pressure on the distribution of intelligence.
Many readers will find these results counterintuitive—the concept of the high-achieving immigrant is deeply ingrained in Americans’ view of our country—but a few moments reflection, plus some additional data, may make the results more understandable.
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Think back to the immigrant at the turn of the century. America was the Land of Opportunity—but that was all. There were no guarantees, no safety nets. One way or another, an immigrant had to make it on his own. Add to that the wrench of tearing himself and family away from a place where his people might have lived for centuries, the terrors of having to learn a new language and culture, often the prospect of working at jobs he had never tried before, a dozen other reasons for apprehension, and the United States had going for it a crackerjack self-selection mechanism for attracting immigrants who were brave, hard-working, imaginative, self-starting—and probably smart. Immigration can still select for those qualities, but it does not have to. Someone who comes here because his cousin offers him a job, a free airplane ticket, and a place to stay is
not
necessarily self-selected for those qualities. On the contrary, immigrating to America can be for that person a much easier option than staying where he is.
Economists have made considerable progress in understanding how the different types of immigration (and all the ones in between) have played out in practice. To begin with, it has been demonstrated beyond much doubt that immigrants as a whole have more steeply rising earnings than American natives of equal age and measured skills and that, after a relatively short adaptation period of ten to fifteen years, immigrants of equal age and education earn as much as natives.
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Here is empirical support for the proposition that immigrants taken as a whole are indeed self-selected for qualities that lead to economic success, and one might expect cognitive ability to be among them.
But the experience of different immigrants at different times has varied drastically. Economist George Borjas has systematized the conditions under which immigrants will be self-selected from the upper and lower tails of the ability distribution. Suppose, he says, that you are living in a foreign country, considering whether to emigrate to America. Presumably a major consideration is your potential income in the United
States versus your income if you stay put. Borjas proposes that this calculation interacts with a person’s earning potential. It makes sense for high-ability people to emigrate when they can reasonably think that they are being underrewarded in their home country, relative to their ability, and that the United States rewards the same level of ability more generously. It makes sense for low-ability people to emigrate when they can reasonably think that the United States not only pays better for the same work but protects them against poor labor market outcomes (in comparison to their birth country) with welfare payments and other entitlements.
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In other words, the United States may be expected to draw high-ability workers from countries that have more extensive welfare states and less income inequality than the United States (such as Western Europe), and will draw low-ability workers from countries that have less extensive welfare states and higher income inequality (such as the poorer countries of the Third World).
Borjas used census data from 1970 and 1980 to examine the experience of immigrants from forty-one countries. In his analysis, he holds constant the individual immigrant’s schooling, age, marital status, health, and the metropolitan area where the immigrant settled. By holding completed schooling constant, Borjas also factored out some of the influence of cognitive ability. But the educational systems in the non-European countries of origin (where we will focus our attention) are much less efficient at identifying talent than the American educational system; many bright immigrants have little formal education. We may think of the unmeasured residual that Borjas did not hold constant as a cluster of personal and cultural qualities, among which is some role for cognitive ability. With this in mind, the Borjas data reveal two important findings.
