Editing The Bell Curve (section)

===Part II. Cognitive Classes and Social Behavior===

The second part describes how cognitive ability is related to social behaviors: high ability predicts socially desirable behavior, low ability undesirable behavior. The argument is made that group differences in social outcomes are better explained by intelligence differences rather than socioeconomic status, a perspective, the authors argue, that has been neglected in research.<ref name="devlin"/>

The analyses reported in this part of the book were done using data from the [[National Longitudinal Surveys|National Longitudinal Survey of Labor Market Experience of Youth]] (NLSY), a study conducted by the [[United States Department of Labor]]'s [[Bureau of Labor Statistics]] tracking thousands of Americans starting in the 1980s. Only [[non-Hispanic white]]s are included in the analyses so as to demonstrate that the relationships between cognitive ability and social behavior are not driven by race or ethnicity.<ref name="devlin"/>

Herrnstein and Murray argue that intelligence is a better predictor of individuals' outcomes than parental socioeconomic status. This argument is based on analyses where individuals' IQ scores are shown to better predict their outcomes as adults than the socioeconomic status of their parents. Such results are reported for many outcomes, including poverty, dropping out of school, unemployment, marriage, divorce, illegitimacy, welfare dependency, criminal offending, and the probability of voting in elections.<ref name="devlin"/>

All participants in the NLSY took the [[Armed Services Vocational Aptitude Battery]] (ASVAB), a battery of ten tests taken by all who apply for entry into the armed services. (Some had taken an IQ test in high school, and the median correlation of the [[Armed Services Vocational Aptitude Battery#Armed Forces Qualification Test|Armed Forces Qualification Test (AFQT)]] scores and those IQ test scores was .81). Participants were later evaluated for social and economic outcomes. In general, Herrnstein and Murray argued, IQ/AFQT scores were a better predictor of life outcomes than [[social class]] background. Similarly, after statistically controlling for differences in IQ, they argued that many outcome differences between racial-ethnic groups disappeared.

{| class="wikitable"
|+ Economic and social correlates of IQ
! IQ || <75 || 75–90 || 90–110 || 110–125 || >125
|-
| US population distribution || 5 || 20 || 50 || 20 || 5
|-
| Married by age 30 || 72 || 81 || 81 || 72 || 67
|-
| Out of labor force more than 1 month out of year (men) || 22 || 19 || 15 || 14 || 10
|-
| Unemployed more than 1 month out of year (men) || 12 || 10 || 7 || 7 || 2
|-
| Divorced in 5 years || 21 || 22 || 23 || 15 || 9
|-
| % of children w/ IQ in bottom decile (mothers) || 39 || 17 || 6 || 7 || –
|-
| Had an [[Illegitimacy|illegitimate]] baby (mothers) || 32 || 17 || 8 || 4 || 2
|-
| Lives in poverty || 30 || 16 || 6 || 3 || 2
|-
| Ever [[incarcerated]] (men) || 7 || 7 || 3 || 1 || 0
|-
| Chronic welfare recipient (mothers) || 31 || 17 || 8 || 2 || 0
|-
| High school dropout || 55 || 35 || 6 || 0.4 || 0
|-
|Scored "Yes" on "Middle Class Values Index"{{refn|group=c|According to Herrnstein & Murray the "Middle Class Values Index" was intended "to identify among the NLSY population, in their young adulthood when the index was scored, those people who are getting along with their lives in ways that fit the middle-class stereotype." To score "Yes" on the index, a NLSY subject had to meet all four of the following criteria:
* Received at least a high-school diploma
* Never interviewed while incarcerated
* Still married to one's first spouse
* ''Men only:'' In the labor force, even if not employed
* ''Women only:'' Never gave birth outside of marriage
Excluded from the analysis were never-married individuals who satisfied all other components of the index, and men who were not in the labor force in 1989 or 1990 due to disability or still being in school.<ref>Herrnstein & Murray (1994) pp. 263–264</ref>}} || 16 || 30 || 50 || 67 || 74
|}
Values are the percentage of each IQ sub-population, among non-Hispanic whites only, fitting each descriptor.<ref>Herrnstein & Murray (1994) pp.&nbsp;171, 158, 163, 174, 230, 180, 132, 194, 247–248, 194, 146, 264 respectively.</ref>

{{reflist|group=c}}