The Bell Curve: Intelligence and Class Structure in American Life (123 page)

25
Gil 1970.

26
Reported in Pelton 1978.

27
Young and Gately 1988, pp. 247, 248.

28
Reported in Pelton 1990-1991.

29
Klein and Stern 1971; Smith 1975.

30
Baldwin and Oliver 1975.

31
Cohen et al. 1966; Johnson and Morse 1968.

32
Smith et al. 1974.

33
Pelton 1978, pp. 612-613.

34
Gil 1970. Recall that Chapter 6 demonstrated that cognitive ability was a stronger predictor of school dropout than socioeconomic status.

35
Brayden et al. 1992.

36
Crittenden 1988, p. 179.

37
Drotar and Sturm 1989.

38
Azar et al. 1984. See Steele 1987 for supporting evidence and Kravitz and Driscoll 1983 for a contrary view.

39
Bennie 1969.

40
Dekovic and Gerris 1992. For findings in a similar vein, see Goodnow et al. 1984; Keller et al. 1984; and Knight and Goodnow 1988. For studies concluding that parental reasoning is not related to social class, see Newberger and Cook 1983.

41
Polansky 1981, p. 43.

42
Most tantalizing of all was a prospective study in Minnesota that gave an extensive battery of tests to young, socioeconomically disadvantaged women before they gave birth. In following up these mothers, two groups were identified: one consisting of thirty-eight young women with highstress life events and adequate care of their children (HS-AC), and the
other of twelve young women with high-stress life events and inadequate care (HS-NC). In the article, data on all the tests are presented in commendable detail, except for IQ. In the “method” section that lists all the tests, an IQ test is not mentioned. Subsequently, there is this passage, which contains everything we are told about the mentioned test: “The only prenatal measure that was not given at 3 months [after birth] was the Shipley-Hartford IQ measure. The mean scores on this measure were 26.9 for the HS-AC group and 23.5 for the HS-NC group (
p
= .064).” Egeland 1980, p. 201. A marginally statistically significant difference with samples of 12 and 38 suggests a sizable IQ difference.

43
Friedman and Morse 1974; Reid and Tablin 1976; Smith and Hanson 1975.

44
Wolfe 1985.

45
Berger 1980.

46
Young 1964, cited by Berger 1980.

47
Wolfe 1985, pp. 473-474.

48
It is understandable that many survey studies cannot obtain a measure of IQ. But virtually all of the studies discussed called for extensive cooperation by the abusive parents. The addition of a short intelligence test would seem to have been readily feasible.

49
The actual quotation is dense but intriguing: “Moreover, they [the British researchers] have shown that parental competence (defined as sensitivity and responsiveness to infant cues, quality of verbalization, and physical contact, and related skills) and adjustment (e.g., low anxiety and adequate flexibility) were distinguishing abilities that moderated the impact of aversive life events” (Wolfe 1985, p. 478).

50
Honesty of the respondents apart, the NLSY data do not address this issue. The question about drinking asked how often a woman drank but not how much at any one time. Since a single glass of wine or beer a few times a week is not known to be harmful, the drinking data are not interpretable.

51
Roughly equal proportions of smokers in the low and high cognitive classes told the interviewers that they had cut down during pregnancy—about 60 percent of smokers in each case.

52
Leonard et al. 1990; Hack and others 1991.

53
“Low birth weight” is operationally defined as infants weighing less than 5.5 pounds at birth. This definition, however, mixes children who are carried to term and are nonetheless underweight with children who are born prematurely (which usually occurs for reasons over which the woman has no control) but who are otherwise of normal weight and development. In the jargon, these babies have a weight “appropriate for gestational age” (AGA). Babies who weighed less than 5.5 pounds but whose weight was equal to or higher than the medical definition of AGA (using the Colorado Intrauterine Growth Charts) were excluded from the analysis.

54
The dip in the proportion for Class V could also be an artifact of small sample sizes. The proportion (computed using sample weights) is produced by 9 out of 116 babies. Sample sizes for the other cognitive classes—II, III, and IV—were much larger: 573, 2,059, and 737, respectively.

55
Hardy and Mellis 1977.

56
Cramer 1987. In a revealing sign of the unpopularity of intelligence as an explanatory variable, Cramer treats years of education as a proxy measure of socioeconomic status. For other studies showing the relationship of education to infant mortality, see Bross and Shapiro 1982; Keller and Fetterly 1978.

57
This is a persistent issue in infant mortality research. There are varying opinions about how important the distinction between neonatal and infant deaths may be. See Eberstein and Parker 1984.

58
Duncan 1993.

59
The calculation assumes that the mother has average socioeconomic back-ground.

60
It measures, among other things, the emotional and verbal responsiveness and involvement of the mother, provision of appropriate play materials, variety in the daily routine, use of punishment, and organization of the child’s environment. The HOME index was created and tested by Bettye Caldwell and Robert Bradley (Caldwell and Bradley 1984).

61
From Class IV to Class II, they were the 48th, 60th, and 68th percentile, respectively. For most of the assessments, including the HOME index, the NLSY database contains raw scores, standardized scores, and centile scores. For technical reasons, it is more accurate to work with standardized scores than percentiles when computing group means, conducting regression analyses, and so forth. On the other hand, centiles are much more readily understood by the ordinary reader. We have conducted all analyses using standardized scores, then converted the final results as reported in the tables back into centiles. Thus, the centiles in the table are
not
those that will be produced by simply averaging the HOME centile scores in the NLSY.

62
We replicated all of these analyses using the HOME index as a continuous variable, and the substantive conclusions from those replications are consistent with the ones reported here.

63
The HOME index has different scoring for children younger than 3 years old, children ages 3 through 5, and children ages 6 and older. We examined the HOME results for the different age groups and found that they could be combined without significant loss of precision for the interpretations we describe in the text. There is some evidence that the mother’s IQ was most important for the home environment of children ages 3 through 5 and least important for children ages 6 and older, but the differences are not dramatic.

64
E.g., Duncan 1993 and almost anything published by the Children’s Defense Fund.

65
We also conducted analyses treating family income as a continuous variable, which showed consistent results.

66
The poverty measure is based on whether the mother was below the poverty line in the year prior to the HOME assessment. Independent variables were IQ, mother’s socioeconomic background, mother’s age, the test year, and the child’s age group (for scoring the HOME index).

67
The table on page 222 shows the predicted odds of being in the bottom decile on the HOME index from a regression equation, using the child’s sample weights, in which the dependent variable is a binary representation of whether an NLSY child had a HOME score in the bottom decile, and the independent variables were mother’s IQ, mother’s socioeconomic background, mother’s age, and nominal variables representing the test year, the age category for scoring the HOME index, poverty in the calendar year prior to the administration of the HOME index, and receipt of AFDC in the calendar year prior to the administration of the HOME index.

“Very low” is defined as two SDs below the mean. Poverty and welfare refer to the calendar year prior to the scoring of the HOME index.

68
The NLSY reported scores on these indexes for infants under 1 year of age, not analyzed here.

69
This statement applies to the full white sample. In the cross-sectional sample, used for the regression results in Appendix 4, the role of birth status (legitimate or illegitimate) was not significant when entered along with poverty and welfare receipt.

70
A technical note that applies to the means reported in the table on page 230 and in Chapter 15. In applying the national norms, the NLSY declined to estimate scores for very low-scoring children not covered in the PPVT’s scoring tables, instead assigning them a score of zero. For purposes of computing the means above and in Chapter 15, we assigned a score of 40 (four SDs below the mean, and the lowest score assigned in the standard tables for scoring the PPVT) to all children with scores under 40.

71
Careful readers may be wondering why white children, who have had less than their fair share of the bottom decile for most of the other indicators, account for fully 10 percent of all NLSY children in the bottom decile. The reason is that the women of the NLSY sample (all races) have had a high proportion of low-IQ children, based on the national norms for the PPVT—fully 23 percent of all NLSY children ages 6 and older when they took the test had IQs of 80 or lower. For whites, 10 percent of the children who have been tested fall into the bottom decile. This news is not quite as bad as it looks. Just because the NLSY mothers were a nationally representative sample of women in a certain age group does not mean that their children are a nationally representative sample of children. But the news is nonetheless worrisome, with implications that are discussed in Chapter 15.

72
See Chapter 4 for the discussion of heritability of IQ.

1
The proportional increases in property crime tracked more or less with the increases in violent crime until the late 1970s. Since then, property crime has moved within a narrow range and in 1992 was actually lower than it had been ten years earlier. This divergence between violent and property crimes is in itself a potentially significant phenomenon that has yet to be adequately explored.

2
For citations of the extensive literature on this subject, see Chaiken and Chaiken 1983; Wilson and Herrnstein 1985. The official statistics may have understated the increase in these “crimes that people consider serious enough to warrant reporting to the police,” insofar as many burglaries, assaults, and street robberies that would have been reported in the 1950s (when there was a reasonable chance that the police would conduct a genuine investigation) are no longer reported in urban areas, where it is taken for granted that they are too minor to compete for limited police resources.

3
A more traditional way to sort the theories is to contrast classical theories,
which depict crime as the rational behavior of free agents, based on costs and benefits, with positive theories, which look for the causes of crime in society or in psychological makeup (for discussion of criminological theory, see, for example, Gottfredson and Hirschi 1990; Wilson and Herrnstein 1985). We are distinguishing only among positive theories, because the notion of criminals as rational agents seems to fit few actual criminals and the role of costs and benefits can readily be absorbed by a positive theory of criminal behavior (see Wilson and Herrnstein 1985, Chap. 2). A distinction similar to ours between psychological and sociological theories is one between “psychiatric” and “criminological” theories in Wessely and Taylor 1991.

4
Freeman 1983; Mayer and Jencks 1989; Wilson and Herrnstein 1985, Chaps. 11, 12.

5
Cleckley 1964; Colaizzi 1989.