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 (65 page)
Upon first consideration, the ways to eliminate those disadvantages seem obvious. Many children of low-income parents grow up in terrible home environments, with little stimulation or nurturing. Surely, it would seem, intelligence would rise if these children were placed in day care environments where professionals provided that stimulation and nurturing. Schools in poor neighborhoods are often run down and chaotic. Isn’t it clear that increasing the investment in schools would pay off in higher scores?
Limitless possibilities for improving intelligence environmentally wait to be uncovered by science: improved educational methods, diets, treatments for disease, prenatal care, educational media, and even medicines to make one smarter. In principle, intelligence can be raised environmentally to unknown limits.
Yet the more one knows about the evidence, the harder it is to be optimistic about prospects in the near future for raising the scores of the people who are most disadvantaged by their low scores. For one thing, it is hard to find new ways to use existing resources that are not already being done. The nurturing of the young—including the cognitive nurturing—is one of the central purposes of human society. That, after all, is what families mainly do. Very high proportions of children already get prenatal care, nutrition, home environments, and classroom environments that are good enough to leave little room for measurable improvement. The grim stories about childhood deprivation involve a small proportion of children. And when it comes to helping that small proportion of children, the results seldom approach
expectations. We may be deeply and properly dissatisfied with the nurturing of American intelligence, but finding solutions that are affordable, politically tolerable, and not already being tried is another matter altogether.
In this chapter, we move through a succession of topics. First we consider the effects of nutrition. We then discuss a sequence of successively more targeted, intense social interventions: education in general, preschool interventions, intensive support for children at risk for retardation, and the most extreme form of social intervention, adoption at birth. We close with our thoughts on what society’s experiences with these interventions should mean for policy in the future.
Most of us have been urged by a parent or grandparent to eat the “brain food,” which seemed invariably to be the most unpalatable thing on the table. This idea of a connection between diet and intelligence has an ancient history going back to
mens sana in corpore sano.
2
In the twentieth century, the plausibility of a connection has been reinforced by the fact that people in affluent countries are larger than their ancestors were, presumably in part because they are eating better. IQ scores, too, have been rising during approximately the same period—the Flynn effect described in Chapter 13. These coincident changes do not prove that better eating makes for smarter people, but count as circumstantial evidence.
For a while, however, scientific research seemed to have weakened the case for any link between nutrition and IQ. The most damaging blow was a study of over 100,000 Dutch men who were born around a time of intense famine in several Dutch cities near the end of World War II.
3
Nineteen years later, the men took intelligence tests as part of the qualification for national military service, and it occurred to scholars to compare the ones who were born in the depths of the famine to those born just before and just after it. Many pregnant women miscarried during the famine, but their surviving sons scored no lower in intelligence than the men born to mothers who had little or no exposure to famine. But as important as this study was, some scientists were not entirely convinced by its negative findings. The Dutch famine was relatively brief—three months or so—and limited to the pre- and perinatal period of the men’s lives. And while the mothers were indeed
starving for calories, their deficiencies in vitamins, minerals, and other dietary elements were perhaps too brief to take a toll.
4
Another approach to the impact of nutrition on cognitive ability is to see whether enriched diets can raise scores. A breakthrough study done in Great Britain in the late 1980s concluded that the answer was yes.
5
David Benton and Gwilym Roberts gave a sample of thirty Welsh 12- to 13-year-old children vitamin and mineral supplements for eight months and compared their test scores with an equal number of their schoolmates getting nonnutritive placebos. The Welsh children were not known to be malnourished, but those getting the supplement gained eight points more in their nonverbal intelligence test scores than those getting the placebo, a large and statistically significant improvement. Verbal scores showed no differential improvement.
6
A recent American confirmation of the Welsh results gave over 600 eighth and tenth graders in several California schools daily pills for thirteen weeks.
7
The pills contained either half the recommended daily allowances (RDA) of a wide assortment of vitamins and minerals, precisely the RDA, twice the RDA, or a placebo. The vitamin and mineral supplement raised scores on most of the nonverbal sub tests of a standard intelligence test.
8
The verbal intelligence test scores again failed to register any benefit, but that is consistent with the Flynn effect: The rising average intelligence scores of nations seem primarily to be on non-verbal tests.
The net average benefit for pills providing one RDA was about four points in nonverbal intelligence in the California study. But this average gain comprised many youngsters who did not benefit at all, mixed with some whose gains exceeded fifteen points. The children who did not benefit were presumably already getting the vitamins and minerals they needed for developing their nonverbal scores in their regular diets. But this is just a hypothesis at present. It remains to be shown whether the gain from vitamins or minerals can be associated with preexisting food deficiencies, let alone which particular dietary ingredients, in what amounts, produce the gains.
9
Youngsters getting exactly the RDA had the largest gain in scores; those taking either more or less of the supplement benefited less, if at all
10
This is not only puzzling but worrisome. Could it rhean that excessive dosages of vitamins and/or minerals harm intellectual functioning? There is no evidence that it does, but at the least, it reinforces the prudence of doing more research before going overboard for vitamin and mineral supplements.
Other Physiological Influences on IQ. Or Are They? Two Further Examples
The physiological environment seems to be associated with IQ in other ways. For example, some studies (hut not all) have found a small decline in IQ of each successive child born to a given woman, even after holding overall family size constant.
12
Is this a matter of the social environment within the family, which changes as new children enter it, or the physiological environment in the uterus, which is both older on average and has a longer history of childbirth with each successive pregnancy? The answer is unclear, and both views have been advanced. But, whichever it is, this would be a genuine environmental effect on intelligence, since the rolls of the genetic dice for the successive offspring of a given mother and father are independent as far as anyone knows.Another environmental and possibly physiological influence on IQ is suggested by data from twins. Among identical twins, the one with the higher IQ is likely to have been heavier at birth.
13
This is part of a more general finding that higher weights at birth are associated with higher IQs in childhood, but the identical twin data decisively prove that the correlation between birth weight and later intelligence has an environmental element, since identical twins are genetic clones.
14
It is less certain that there are no social factors here: People may treat twin babies differently if one is plumper than the other. Training mothers in how to be more attentive to their low-birth-weight babies seems, in fact, to raise later IQ, at least up to the age of 7.
15
This caution is reinforced by the inconsistency of the nutritional effect on IQ. Many studies that seem to be well-conducted variations of the successful ones have failed to demonstrate any effect on IQ at all.
11
The reasonable middle ground at this point is to conclude that providing children with the recommended daily allowance of vitamins is a good idea for many reasons and might also have a helpful effect on IQ.
The almost reflexive reaction of most people when they hear about the below-average test scores among children in the bottom of the socioeconomic distribution is that of course they have low scores because they have gotten poor educations. Improve the schools, it is assumed, and the scores will rise.
There are a number of problems with this assumption. One basic error is to assume that new educational opportunities that successfully raise the average will also reduce
differences
in cognitive ability. Consider trying to raise the cognitive level by putting a public library in a community that does not have one. Adding the library could increase the average intellectual level, but it may also spread out the range of scores by adding points to the IQs of the library users, who are likely to have been at the upper end of the distribution to begin with. The literature on such “aptitude-treatment interactions” is large and complex.
16
For example, providing computer assistance to a group of elementary school children learning arithmetic increased the gap between good and bad students;
17
a similar effect was observed when computers were used to teach reading;
18
the educational television program, “Sesame Street” increased the gap in academic performances between children from high- and low-status homes.
19
These results do not mean that such interventions are useless for the students at the bottom, but one must be careful to understand what is and is not being improved: The performance of those at the bottom might improve, but they could end up even further behind their brighter classmates.
A second broad difficulty with relying on improvements in education is that although they make some difference in IQ, the size of the effect is small. This conclusion is supported by evidence from both natural variation in education and planned educational experiments.
Parents buying new houses often pick the neighborhood according to the reputation of the local schools. Affluent parents may spend tens of thousands of dollars to put their children through private schools. Tell parents that the quality of the schools doesn’t matter, and they will unanimously, and rightly, ignore you, for differences in schools do matter in many important ways. But in affecting IQ, they do not matter nearly as much as most people think.
This conclusion was first and most famously reached by a study that was expected to demonstrate just the opposite. The study arose out of a mandate of the Civil Rights Act of 1964 to examine how minority groups are affected by educational inequalities. The result was a huge national survey, with a sample that eventually numbered 645,000 students, led by the eminent sociologist James S. Coleman. His researchers measured school quality by such objective variables as credentials of the
teachers, educational expenditures per pupil, and the age and quality of school facilities.
Because the schools that most minority children attended were measurably subpar in facilities and staff, it was assumed that the minority children fortunate enough to attend better schools would also show improved cognitive functioning. But the report, issued in July 1966, announced that it had failed to find any benefit to the cognitive abilities of children in public primary or secondary schools that could be credited to better school quality.
20
The usual ways in which schools tried to improve their effectiveness were not likely to reduce the cognitive differences among individual children or those between ethnic groups.
The Coleman report’s gloomy conclusions were moderated in subsequent analyses that found some evidence for marginal benefits of school quality on intellectual development.
21
Coleman himself later concluded that parochial schools generally do a better job of developing the cognitive abilities of their students than public schools, which pointed to at least some factor in schooling that might be exploited to improve intelligence.
22
Yet the basic conclusion of the report has stood the test of time and criticism: Variations in teacher credentials, per pupil expenditures, and the other objective factors in public schools do not account for much of the variation in the cognitive abilities of American school children.
23
The several hundred thousand children assessed in the Coleman study had not been subjects in educational experiments. They were just students in several thousand local schools. The schools varied in quality, as they inevitably will.
24
Some schools, usually in prosperous urban or suburban districts, got (and still get) more money, more teachers with better qualifications, newer school buildings, and the like. Poorer or rural districts usually made (and make) do with less. The Coleman report, in other words, is one of a species of educational research that draws on
natural variation—
variation that is occurring spontaneously rather than by design.
Looking at the effects of natural variation has advantages as a research strategy. One is that this kind of research does not require new investments of time and money to intervene in schools. The intervening has already been done at someone else’s expense. The disadvantage of such studies is that the variation is often narrow—an example of the restriction of range problem that we described in Part I. If almost all classes have, say, between twenty-five and thirty-five children in them,
then looking at natural variation cannot reveal what would happen in classes with five or ten children in them. The Coleman report did not prove that educational reform is always futile, but that, on the whole, America had already achieved enough objective equalization in its schools by 1964 so that it was hard to pick up any effects of unequal school quality. The Coleman report tells us that the cognitive ability differences among individuals and groups alike on a national scale cannot be reduced much by further attempts to equalize the kinds of bricks-and-mortar factors and teacher credentials that school boards and taxpayers most often concern themselves with.
