The Bell Curve: Intelligence and Class Structure in American Life

by Richard J. Herrnstein

  We realize that once again we are contradicting what everyone knows, which is that “child abuse and neglect afflict all communities, regardless of race, religion, or economic status,” to pick one formulation of this common belief.19 And in a narrow technical sense, such statements are correct, insofar as neglect and abuse are found at every social and economic level, as is every other human behavior. It is also correct that only a small minority of parents among the poor and disadvantaged neglect or abuse their children. But the way such statements are usually treated in the media, by politicians, and by child advocacy groups is to imply that child neglect and abuse are spread evenly across social classes, as if children have about an equal chance of being abused or neglected whether they come from a rich home or a poor one, whether the mother is a college graduate or a high school dropout. And yet from the earliest studies to the present, malparenting has been strongly associated with socioeconomic class.

  The people who argue otherwise do not offer data to make their case. Instead, they argue that child neglect and abuse are reported when it happens to poor children but not rich ones. Affluent families are believed to escape the reporting net (by using private physicians, for example, who are less likely to report abuse). Social service agencies are said to be reluctant to intervene in affluent families.20 Poor people are likely to be labeled deviant for behaviors that would go unnoted or unremarked in richer neighborhoods.21 People are likely to think the worst of socially unattractive people and give socially attractive people the benefit of the doubt.22

  Studies spread over the last twenty years have analyzed reporting bias in a variety of ways, including surveys to identify abuse that goes unreported through official channels. The results are consistent: The socioeconomic link with maltreatment is authentic.23 Probably the link is stronger for neglect than for abuse.24 But specifying exactly how strongly socioeconomic status and child maltreatment are linked is difficult because of the genuine shortcomings of official reports and because so many different kinds of abuse and neglect are involved. The following numbers give a sense of the situation:

  In an early national study (using data for 1967) 60 percent of the families involved in abuse incidents had been on welfare during or prior to the study year.25

  In data on 20,000 validated reports of child abuse and neglect collected by the American Humane Association for 1976, half of the reported families were below the poverty line and most of the rest were concentrated just above it.26

  In a 1984 study of child maltreatment in El Paso, Texas, 87 percent of the alleged perpetrators were in families with incomes under $18,000, roughly the bottom third of income. Seventy-three percent of the alleged female perpetrators were unmarried.27

  In the federally sponsored National Incidence Study in 1979, which obtained information on unreported as well as reported cases, the families of 43 percent of the victims of child abuse or neglect had an income under $7,000, compared to 17 percent of all American children. Only 6 percent of the abusive or neglectful families had incomes of $25,000 or more.

  The 1986 replication of the National Incidence Study found that the rate of abuse and neglect among families with incomes under $15,000 was five times that of families with incomes above $15,000. Only 6 percent of the families involved in neglect or abuse had incomes above the median for all American families.28

  Other Precursors of Maltreatment

  Premature births, low birth weight, and illegitimacy also have links with maltreatment. Studies in America and Britain have found rates of low birth weight among abused children running at three to four times the national average.29 Prematurity has been found to be similarly disproportionate among abused children.30 The proportion of neglected children who are illegitimate has run far above national averages in studies from the early 1960s onward. More than a quarter of the neglected children in the mid-1960s were illegitimate, for example—almost four times the national proportion.31 In a British sample, 36 percent of the neglected children were illegitimate compared to 6 percent in the control group.32

  Given the one-sided nature of the evidence, why has the “myth of classlessness,” in Leroy Pelton’s phrase, been so tenacious? Pelton himself blamed social service professionals and politicians, arguing that both of these powerful groups have a vested interest in a medical model of child abuse, in which child abuse falls on its victims at random, like the flu.33 Pelton does not mention another reason that seems plausible to us: Child abuse and neglect are held in intense distaste by most Americans, who feel great hostility toward parents who harm their children. People who write about malparenting do not want to encourage this hostility to spill over into hostility toward the poor and disadvantaged.

  Whatever the reasons, the myth of classlessness is alive and well. It is a safe bet that at the next Senate hearing on a child neglect bill, witnesses and senators alike will agree that neglect and abuse are scattered throughout society, and the next feature story on child neglect you see on the evening news will report, as scientific fact, that child neglect is not a special problem of the poor.

  PARENTAL IQ AND PARENTING

  In all of these studies of socioeconomic status and parenting, the obvious but usually ignored possibility has been that the parents’ cognitive ability, not their status, was an important source of the differences in parenting styles and also an important source of the relationship between malparenting and children’s IQs. Indeed, even without conducting any additional studies, some sort of role for cognitive ability must be presupposed. If cognitive ability is a cause of socioeconomic status (yes) and if socioeconomic status is related to parenting style (yes), then cognitive ability must have at least some indirect role in parenting style. The same causal chain applies to child maltreatment.

  Direct evidence for a link with IQ is sparse. Even the educational attainment of the abusing parents is often unreported. But a search of the literature through the early 1990s uncovered a number of fragments that point to a potentially important role for cognitive ability, if we bear in mind that cognitive ability is a stronger predictor of school dropout than is socioeconomic status (Chapter 6):

  In Gil’s national study of child abuse reports, more than 65 percent of the mothers and 56 percent of the fathers had not completed high school.34

  A study of 480 infants of women registering for prenatal care at an urban hospital for indigent persons and their children found that the less educated mothers even within this disadvantaged population were more likely to neglect their babies.35

  Three studies of child maltreatment in a central Virginia city of 80,000 people found that neglecting families had an average eighth-grade education, and almost three-quarters of them had been placed in classes for the mentally retarded during their school years. In contrast with the neglecting families, the abusing families tended to be literate, high school graduates, and of normal intelligence.36

  A study of fifty-eight preschool children of unspecified race in the Cleveland area with histories of failure to thrive found that their mothers’ IQs average was 81.37 No comparison group was available in this study, but a mean of 81 indicates cognitive functioning at approximately the 10th centile.

  A study of twenty abusive or neglectful mothers and ten comparison mothers from inner-city Rochester, New York, found that maltreating and nonmaltreating mothers differed significantly in their judgment about child behavior and in their problem-solving abilities.38

  A clinical psychological study of ten parents who battered their children severely (six of the children died) classified five as having a “high-grade mental deficiency” (mentally retarded), one as dull, and another as below average. The remaining three were classified as above average.39

  A quantitative study of 113 two-parent families in the Netherlands found that parents with a high level of “reasoning complexity” (a measure of cognitive ability) responded to their children more flexibly and sensitively, while those with low levels of reasoning complexity were more authoritarian and rigid,
independent of occupation and education.40

  The most extensive clinical studies of neglectful mothers have been conducted by Norman Polansky, whose many years of research began with a sample drawn from rural Appalachia, subsequently replicated with an urban Philadelphia sample. He described the typical neglectful mother as follows:

  She is of limited intelligence (IQ below 70), has failed to achieve more than an eighth-grade education, and has never held … employment…. She has at best a vague, or extremely limited, idea of what her children need emotionally and physically. She seldom is able to see things from the point of view of others and cannot take their needs into consideration when responding to a conflict they experience.41

  The specific IQ figure Polansky mentions corresponds to the upper edge of retardation, and his description of her personality invokes further links between neglect and intelligence.

  Another body of literature links neglectful and abusive parents to personality characteristics that have clear links to low cognitive ability.42 The most extensive evidence describes the impulsiveness, inconsistency, and confusion that mark the parenting style of many abusive parents.43 The abusive parents may or may not punish their children more often or severely in the ordinary course of events than other parents (studies differ on this point),44 but the abuse characteristically comes unpredictably, in episodic bursts. Abusive parents may punish a given behavior on one occasion, ignore it on another, and encourage it on a third. The inconsistency can reach mystifying proportions; one study of parent-child interactions found that children in abusing families had about the same chance of obtaining positive reinforcement for aggressive behaviors as for pro-social behaviors.45

  The observed inconsistency of abusing parents was quantified in one of the early and classic studies of child abuse by Leontine Young, Wednesday’s Children. By her calculations, inconsistency was the rule in all of the “severe abuse” families in her sample, in 91 percent of the “moderate abuse” families, 97 percent of the “severe neglect” families, and 88 percent of the “moderate neglect” families.46 In one of the most extensive literature reviews of the behavioral and personality dimensions of abusive parents (as of 1985), the author concluded that the main problem was not that abusive parents were attached to punishment as such but that they were simply incompetent as parents.47

  One might think that researchers seeing these malparenting patterns would naturally be inspired to look at the parents’ intelligence as a predictor. And yet in that same literature review, examining every rigorous American study on the subject, the word intelligence (or any synonym for it) does not occur until the next-to-last page of the article.48 The word finally makes its appearance as the literature review nears its end and the author turns to his recommendations for future research. He notes that in an ongoing British prospective study of parenting, “mothers in their Excellent Care group, for example, were found to be of higher intelligence … than parents in their Inadequate Care group,” and then describes several ways in which the study found that maternal intelligence seemed to compensate for other deprivations in the child’s life.49

  With such obvious signals about such tragic problems as child neglect and abuse, perhaps an editorial comment is appropriate: The reluctance of scholars and policymakers alike to look at the role of low intelligence in malparenting may properly be called scandalous.

  MATERNAL IQ AND THE WELL-BEING OF INFANTS

  Combined with the literature, the NLSY lends further insight into good and bad parenting. We begin with information on the ways in which women of varying cognitive ability care for their children and then turn to the outcomes for the children themselves.

  Prenatal Care

  In most of the ways that are easily measurable, most white women in the different cognitive classes behaved similarly during pregnancy. Almost everyone got prenatal care, and similar proportions in all cognitive classes began getting it in the early months. If we take the NLSY mothers’ self-descriptions at face value, alcohol consumption during pregnancy was about the same across the cognitive classes.50 The risk of miscarriage or a stillbirth was also spread more or less equally across cognitive classes.

  Smoking was the one big and medically important difference related to maternal intelligence: The smarter the women, the less they smoked while they were pregnant. Fifty-one percent of the women in the bottom two cognitive classes smoked, and 19 percent of them admitted to smoking more than a pack a day. In the top two cognitive classes, only 16 percent of the white women in the NLSY smoked at all, and only 4 percent admitted to smoking more than a pack a day. In Class I, no one smoked. Smarter pregnant women smoked less even after controlling for their socioeconomic backgrounds. Higher levels of education, independent of intelligence, also deterred pregnant women from smoking.51

  Low Birth Weight

  We focus here on an indicator that is known to have important implications for the subsequent health, cognitive ability, and emotional development of the child and is also affected to some degree by how well women have cared for themselves during pregnancy: low birth weight.52 Low birth weight is often caused by behaviors during pregnancy, such as smoking, drug or alcohol abuse, or living exclusively on junk food, that are seldom caused by pure ignorance these days. The pregnant woman who never registers the simple and ubiquitous lessons about taking care of herself and her baby, fails to remember them, or fails to act on them could be willfully irresponsible or in the grip of an irresistible addiction to drugs or junk food, but slow comprehension, a short time horizon, and difficulty in connecting cause and effect are at least as plausible an explanation, and all of these betoken low IQ.

  A low-birth-weight baby is defined in these analyses as an infant weighing less than 5.5 pounds at birth, excluding premature babies whose weight was appropriate for their gestational age.53 The experience of the NLSY mothers is shown in the table below. There does not appear to be much of a relationship between intelligence and low birth weight; note the high rate for babies of mothers in Class I (which is discussed in the accompanying box). But the table obscures a strong overall relationship between IQ and low birth weight that emerges in the regression analysis shown in the following figure.

  Low Birth Weight Among White Babies

  Cognitive Class Incidence per 1,000 Births

  I Very bright 50

  II Bright 16

  III Normal 32

  IV Dull 72

  V Very dull 57

  Population average 62

  A white mother’s IQ has a significant role in determining whether her baby is underweight while her socioeconomic background does not

  Note: For computing the plot, age and either SES (for the black curve) or IQ (for the gray curve) were set at their mean values.

  A low IQ is a major risk factor, whereas the mother’s socioeconomic background is irrelevant. A mother at the 2d centile of IQ had a 7 percent chance of giving birth to a low-birth-weight baby, while a mother at the 98th percentile had less than a 2 percent chance.

  Adding Poverty. Poverty is an obvious potential factor when trying to explain low birth weight. Overall, poor white mothers (poor in the year before birth) had 61 low-birth-weight babies per 1,000, while other white mothers had 36. But poverty’s independent role was small and statistically insignificant, once the other standard variables were taken into account. Meanwhile, the independent role of IQ remained as large, and that of socioeconomic background as small, even after the effects of poverty were extracted.

  Can Mothers Be Too Smart for Their Own Good?

  The case of low birth weight is the first example of others you will see in which the children of white women in Class I have anomalously bad scores. The obvious, but perhaps too obvious, culprit is sample size. The percentage of low-birth-weight babies for Class I mothers, calculated using sample weights, was produced by just two low-birth-weight babies out of seventy-four births.54 The sample sizes for white Class I mothers in the other analyses that produce anomalous results are als
o small, sometimes under fifty and always under one hundred, while the sample sizes for the middle cognitive classes number several hundred or sometimes thousands.

  On the other hand, perhaps the children of mothers at the very top of the cognitive distribution do in fact have different tendencies than the rest of the range. The possibility is sufficiently intriguing that we report the anomalous data despite the small sample sizes, and hope that others will explore where we cannot. In the logistic regression analyses, where each case is treated as an individual unit (not grouped into cognitive classes), these problems of sample size do not arise.

  Adding mothers age at the time of birth. It is often thought that very young mothers are vulnerable to having low-birth-weight babies, no matter how good the prenatal care may be.55 This was not true in the NLSY data for white women, however, where the mothers of low-birth weight babies and other mothers had the same mean (24-2 years).

  In sum, neither the mother’s age in the NLSY cohort, nor age at birth of the child, nor poverty status, nor socioeconomic background had any appreciable relationship to her chances of giving birth to a low-birth-weight baby after her cognitive ability had been taken into account.