The Bell Curve: Intelligence and Class Structure in American Life (31 page)

None of these reasons has an obvious connection with cognitive ability. They could be valid without necessarily affecting the independent prophylactic role that being smart plays in preventing (or perhaps simply delaying) divorce. And so indeed it worked out in the NLSY. Given a young person of average IQ and socioeconomic background, the probability of divorce within the first five years of marriage was lowest for those who at age 14 had been living with both parents (20 percent), a bit higher for those who had been living with a remarried parent (22 percent), and higher still for those living with an un-remarried or never-married mother (25 percent)
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These are not large effects, however, and are not significant in a statistical sense. We can say only that the results supported the general proposition that, when it comes to raising children who will themselves stay married, two adults as parents are generally better than one and that two biological parents in the household are better than one or none. But it is worth noting that the introduction of these variables did nothing to change the importance of the rest of the variables. Higher cognitive ability conferred just about as much protection from, and higher status just as much risk for, divorce as in the preceding analyses.

The NLSY gives us a window on the early years of marriage, though not necessarily about marriage as a whole. Based on national divorce rates, we know that most of the divorces that the members of the NLSY will
experience have yet to occur. We will have to wait and see what happens to the NLSY sample in later years.

One final point about the divorce results is worth noting, however. These findings may help explain the common observation that divorce is less likely when the husband has high education, income, or socioeconomic status or that marriages are more likely to fall apart if they start when the couple is afflicted with unemployment.
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If we had showed a breakdown of divorce rates in the NLSY by social and economic measures alone, we too would have shown such effects. But each of those variables is correlated with cognitive ability, and the studies that examine them almost never include an independent measure of intelligence per se. Some portion of what has so often been observed about the risk factors for divorce turns out to be more narrowly the result of low cognitive ability.

Childbearing touches on one of the most sensitive topics in the study of intelligence and its social consequences: fertility patterns among the smart and the dumb, and their possible long-term effects on the intellectual capital of a nation’s population. We devote a full chapter to this topic (Chapter 15) in the portion of the book dealing with the national, multiracial perspective. In this chapter, the focus is on family problems, and one of the leading current problems is the failure of two-parent families to form in the first place, as denoted by births to single women—illegitimacy.

We use the older term “illegitimacy” in favor of the phrases currently in favor, “out-of-wedlock births” or “births to single women,” because we think that, in the long run, the word illegitimacy will prove to be the right one. We are instructed in this by the anthropologist Bronis-law Malinowski. In his research early in the century, Malinowski observed a constant running throughout the rich diversity of human cultures and indeed throughout history. He decided that this amounted to “a universal sociological law” and called it the “principle of legitimacy.” No matter what the culture might be, “there runs the rule that the father is indispensable for the full sociological status of the child as well as of the mother, that the group consisting of a woman and her offspring is sociologically incomplete and illegitimate.”
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The rule applied alike to East or West, primitive cultures or advanced ones, cultures
where premarital sex was accepted or banned, where children were considered an asset or a burden, where fathers could have one wife or many. Despite our faith that Malinowski was observing something that will once again be considered true about human societies, the contemporary Western democracies, including the United States, seem intent on proving Malinowski wrong, as shown in the next figure.

The illegitimacy revolution

Sources:
Various editions of the Natality volume of
Vital Statistics,
compiled annually by the Public Health Service.

In the seventy-one years from 1920 to 1990, the proportion of children born to single women in the United States went from less than 3 percent, roughly where it had been throughout American history, to 30 percent.
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It would have been about 6 percent had the trendline established from 1920 to 1952 remained unchanged. The trendline shifted upward during the 1950s, but not dramatically. If we had maintained the trendline established from 1952 to 1963, the United States would have had about 11 percent of births out of wedlock in 1991. Instead, the figure was 30 percent, the result of a steep, sustained increase that gatlered
steam in the mid-1960s and continued into the early 1990s. The increase for the most recent available year, 1991, was one of the largest in history. There are no signs as we write that illegitimacy is reaching an asymptote.

Anyone who is trying to understand social trends must also realize that the magic of compound interest has created an even more explosive rise in the population of unmarried mothers and children. In 1960, for example, there were just 73,000 never-married mothers between the ages of 18 and 34. In 1980, there were 1.0 million.
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In 1990, there were approximately 2.9 million.
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Thus the illegitimacy ratio increased by sixfold from 1960 to 1990—bad enough—but the number of never-married mothers increased fortyfold. From just 1980 to 1990, while the illegitimacy ratio was increasing by half, the number of unmarried mothers almost tripled.

If IQ is a factor in illegitimacy, as we will conclude it is, it must be in combination with other things (as common sense would suggest), because IQ itself has not changed nearly enough in recent years to account for the explosive growth in illegitimacy.
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But we will also be exploring the possibility that some of these “other things” that have changed in the last three decades—broken homes and the welfare system being prime suspects—interact with intelligence, making it still more likely than before that a woman of low cognitive ability will have a baby out of wedlock.

Among other reasons that cognitive ability may be related to illegitimacy, we have this causal model in mind: The smarter a woman is, the more likely that she deliberately decides to have a child and calculates the best time to do it. The less intelligent the woman is, the more likely that she does not think ahead from sex to procreation, does not remember to use birth control, does not carefully consider when and under what circumstances she should have a child. How intelligent a woman is may interact with her impulsiveness, and hence her ability to exert self-discipline and restraint on her partner in order to avoid pregnancy. The result is a direct and strong relationship between high intelligence and the likelihood that a child is conceived after marriage, and between low intelligence and the likelihood that the child will be born out of wedlock.

There are, of course, objections to this explanation. Some will bristle at our identification of conception within marriage with the intelligent thing to do. But is it really controversial or even arguable? Under what circumstances can a thoughtful, coolheaded appraisal lead one to conclude that it is better to conceive a child outside marriage? If such circumstances exist, are they not exceptional? Perhaps a woman wants to conceive a child out of marriage, but how likely is it that a disinterested person would consider it to be in the best interest of all concerned, including the child’s?

We begin our exploration with the overall numbers. First, how many white women are engaging in this behavior? As the next table shows, the differences among the cognitive classes are extremely large. Only 2 percent of white women in Class I had given birth to an illegitimate child as of the 1990 interview, compared to 32 percent of the women in Class V.

Now we switch lenses. Instead of asking how many women have ever had an illegitimate baby, we ask what proportion of first babies born to white women are illegitimate. The next table shows the results. The proportions of illegitimate first births in the top two cognitive classes are nearly the same, rounding to 7 percent—about half the proportion for Class III, a third of the proportion for Class IV, and a sixth of the proportion for Class V. Illegitimacy is again conspicuously concentrated in the lowest cognitive groups.

The relationship between intelligence and illegitimacy is strong not only in these basic respects, but also in more subtle ways, as the numbers based on the women’s first births, shown in the next table, reveal. Not only are children of mothers in the top quartile of intelligence (Classes I and II) more likely to be born within marriage, they are more likely to have been conceived within marriage (no shotgun wedding). The differences among the cognitive classes are large, as if they lived in different worlds. For the women in Class V, only 47 percent of the first children were conceived after a marriage ceremony; for the women in Class I, 89 percent.

The table makes a strong prima facie case for a relationship between cognitive ability and illegitimacy. The question is whether it survives scrutiny when we introduce other factors into the analysis.
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The socioeconomic background of a young woman was traditionally thought to be crucial in determining whether she bore a child out of wedlock. The old-fashioned view of illegitimacy was that it occurred mostly among girls from the lower classes, with occasional and scandalous slip-ups by higher-class “good girls” who “got in trouble.” But during the last few decades, as births outside marriage became more common and as examples proliferated of film stars and career women who were choosing to have babies without husbands, an alternative view spread. The sexual revolution had obviously penetrated to all levels of society, it was argued, and births out of wedlock were occurring at all levels of our sexually liberated society.

There were never any systematic data to support this view, but neither did scholars rush to check it out. A 1980 article in the
American Sociological Review
on education and fertility reported that white women with less than a high school education were twenty times more likely to have a child out of wedlock than white women with at least a college degree, but illegitimacy was only a side issue in the article and the datum never got noticed in the public dialogue.
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The relationship of teenage illegitimacy to social and cognitive factors was first treated in detail in an analysis of the High School and Beyond survey published by the RAND Corporation in 1988.
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The report revealed that more than three-quarters of the teenage girls in this national sample who had babies while they were still of high school age came from families in the bottom half of the socioeconomic stratum. More than half came from the bottom quartile. This finding also held true among just the white teenage girls who had babies out of wedlock, with 70 percent coming from the bottom half of the socioeconomic distribution and only 12 percent from the top quartile.
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The RAND study was also the first to reveal that cognitive ability played an important role, independent of socioeconomic status.
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