The Bell Curve: Intelligence and Class Structure in American Life
Page 83
23 Rindfuss et al. 1980.
24 Abrahamse et al. 1988. The analysis is based on a sample of 13,061 girls who were sophomores in 1980 at the time of the High School and Beyond (HS&B) baseline survey and also responded to the first follow-up questionnaire in 1982.
25 The exact figures, going from the bottom to the top quartile in socioeconomic status, are 38.7 percent, 29.7 percent, 19.9 percent, and 11.7 percent, based on weighted data, computed by the authors from the HS&B database. Figures reported here and on other occasions when we refer to the RAND study will sometimes show minor discrepancies with the published account, because Abrahamse et al. used imputed figures for certain variables, based on schoolwide measures, when individual data were missing. Our calculations do not use any imputed figures. As in the RAND study, all results are based on weighted analyses using the HS&B population weights.
26 For mothers of an illegitimate baby, the mean on the test of cognitive ability was .73 SD below the mean for all girls who had babies, and .67 SD below the mean for all white girls (mothers and nonmothers).
27 Limiting the analysis to first births avoids a number of technical problems associated with differential number of children per woman by cognitive and socioeconomic class. Analyses based on all children born by the 1990 interview show essentially the same results, however. We also conducted a parallel set of analyses using as the dependent variable whether the woman had ever given birth to a child out of wedlock (thereby adding women without any children at all to the analysis). The interpretations of the results were not markedly different for any of the analyses presented in the text.
28 We are, as usual, comparing the effects of a shift equal to ±2 SDs around the mean for both independent variables, cognitive ability and socioeconomic status.
29 Bachu 1993, Table J.
30 Bachu 1993, Table J.
31 The comparable probabilities given parental SES standard scores of-2 and +2 were 31 percent and 19 percent.
32 The literature is extensive. Two recent reviews of the literature are Moffitt 1992 and Murray 1993. See also Murray 1994.
33 The writing on this topic is much more extensive for the black community than the white. See, for example, Anderson 1989; Duncan and Hoffman 1990; Furstenberg et al. 1987; Hogan and Kitagawa 1985; Lundberg and Plotnick 1990; Rowe and Rodgers 1992; Teachman 1985; Moffitt 1983.
34 For a detailed presentation of this argument, see Murray 1986b.
35 An analysis based not on the dichotomous variable, poverty, but on income had essentially the same outcome.
36 When we repeat the analysis yet again, adding in the presence of the biological father, these results are sustained. Poverty and cognitive ability remain as important as before; the parents’ poor socioeconomic status does not increase the chances of illegitimate babies.
Chapter 9
1 Louchheim 1983, p. 175. See also Liebmann 1993.
2 Bane and Ellwood 1983; Ellwood 1986b; Hoffman 1987.
3 The studies are reviewed in Bendick and Cantu 1978.
4 Hopkins et al. 1987.
5 This figure includes women not reflected in the table who did not go on AFDC within the first year after birth, received welfare at some later date, but did not become chronic recipients.
6 In all cases, we limit the analysis to women for whom we have complete data and whose child was born prior to January 1,1989. We also conducted this analysis with another definition of short-term recipiency, limiting the sample to women whose children had been born prior to 1986, divided into women who had never received welfare subsequently and women who had received welfare up to half of the years that they were observed but did not qualify as chronic welfare recipients. The results were similar to the ones reported in the text, with a large negative effect of IQ and an insignificant role for SES.
7 Bane and Ellwood 1983; Ellwood 1986a; Murray 1986a.
8 Ellwood 1986a; Murray 1986a.
9 We conducted a parallel analysis comparing chronic welfare recipients with all other mothers, including those who had been on welfare but did not qualify as chronic. There are no important differences in interpretation for the results of the two sets of analyses.
10 Among all white women, only 16 percent had not gotten a high school diploma, and 27 percent had achieved at least a bachelor’s degree.
11 Once again, this analysis has to be based on women with a high school diploma because there was no way to analyze welfare recipiency among white women with B.A.s. Only two white women with B.A.s in the NLSY had become chronic recipients. But for the high school graduates, the effect of parental SES is modest—slightly smaller than the independent effect of cognitive ability. This pattern was generally shared among women who had gone on to get their GED (recall that people with a GED are not included in the high school sample).
12 Some of the obvious explanations are not as important as one might expect. For example, most of the high school dropouts who became chronic welfare recipients were not poor; only 36 percent of them had been below the poverty line in the year before birth. Nor is it correct to assume that all of them had babies out of wedlock; nearly half (46 percent) of their first babies had been born within marriage. But 70 percent of the chronic welfare recipients among the high school dropouts had had their first child before they turned 19, which means that some very large proportion of them had the baby before they would normally have graduated. Among high school dropouts who had not had a child before their nineteenth birthday, the independent relationships of IQ and socioeconomic ststus shift back toward the familiar pattern, with the effects of IQ being much larger than those of socioeconomic status.
13 Indeed, the teenage mothers who did not become chronic welfare recipients had a slightly lower mean IQ than those who did (23d centile versus 26th centile). Meanwhile, the ones who did not become welfare recipients at all had a fractionally higher mean socioeconomic status than the ones who did (27th centile versus 26th).
14 Having a high school diploma was an important variable in all of the analyses of welfare, over and above the effects of either cognitive ability or socioeconomic background, and regarding either short-term or chronic welfare recipiency. The question is whether the high school diploma—and we are referring specifically to the high school diploma, not an equivalency degree—reflects a cause or a symptom. Does a high school education prepare the young woman for adulthood and the world of work, thereby tending to keep her off welfare? Or does the act of getting a high school diploma reflect the young woman’s persistence and ability to cope that tend to keep her off welfare? It is an important question; unfortunately, we were unable to think of a way to answer it with the data we have.
15 All are mutually exclusive groups. Criteria follow those for temporary and chronic welfare recipiency defined earlier.
Chapter 10
1 Anderson 1936.
2 See Bronfenbrenner 1958, p. 424, for a review of the literature through the mid-1950s. For a recent empirical test, see Luster et al. 1989.
3 Kohn 1959.
4 Kohn 1959.
5 Kohn 1959, p. 366.
6 Heath 1983.
7 The study also includes “Trackton,” a black lower-class community.
8 Heath 1982, p. 54.
9 Heath 1981, p. 61.
10 Heath 1982, p. 62.
11 Heath 1982, p. 63.
12 Gottfried 1984, p. 330.
13 Kadushin 1988, p. 150.
14 Drawn from Kadushin, 1988, pp. 150-151. Formally, neglect is defined by one of the leading authorities, Norman Polansky, as a situation in which the caretaker “permits the child to experience avoidable present suffering and/or fails to provide one or more ingredients generally deemed essential for developing a person’s physical, intellectual or emotional capacities.” Quoted in Kadushin, p. 150.
15 Kaplun, 1976; Smith and Adler, 1991; Steele 1987; Trickett et al. 1991.
16 E.g., Azar et al. 1984. For a discussion of weaknesses in the state of knowledge about causes and an ar
gument for continuing to treat abuse and neglect separately, see Cicchetti and Rizley 1981. See also Bousha and Twentyman 1984; Herrenkohl et al. 1983.
17 Some recent reviews of the evidence on causation are Hegar and Yung-man 1989; Polansky 1981; Zuravin 1989. The intergenerational explanation is one of the most widely known. For a review of the literature and some important qualifications to assumptions about intergenerational transmission, see Kaufman and Zigler 1987.
18 Besharov 1991.
19 D. Besharov and S. Besharov, quoted in Pelton 1978, p. 608.
20 Parke and Collmer 1975.
21 Coser 1965; Horowitz and Liebowitz 1969.
22 Jensen and Nicholas 1984; Osborne et al. 1988.
23 Leroy H. Pelton’s literature review is still excellent on the studies through the mid-1970s, as is Garbarino’s. See Garbarino and Crouter 1978; Pelton 1978. Also see Straus and Gelles 1986; Straus et al. 1980; Trickett et al. 1991. Unless otherwise noted, the literature review in this section is not restricted to whites.
24 U.S. Department of Health and Human Services 1988; Wolfe 1985.
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 pov
erty 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.
Mother’s IQ Mother’s Socioeconomic Background In Poverty? On Welfare? Odds of Being in the Bottom Decile on the HOME Index
Average Average No No 4%
Average Average Yes No 8%
Average Average No Yes 9%
Average Average Yes Yes 16%
Average Very low No No 7%
Average Very low Yes No 12%
Average Very low No Yes 14%
Average Very low Yes Yes 24%
Very low Average No No 10%
Very low Average Yes No 18%
Very low Average No Yes 21%
Very low Average Yes Yes 34%
“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.