Do Assortative Mating Patterns for IQ Block Upward Social Mobility? Wendy Johnson University of Edinburgh William G. Iacono and Matt McGue University of Minnesota April 19, 2014

Assortative Mating for IQ Generally runs.3 to.4 Source is most likely educational assortment – Rather than IQ directly – Increases genetic variance and population stratification Generally assumed to be stable across the range of IQ, but what if not? – Interesting social phenomenon in own right – Would especially stratify population where highest

Minnesota Twin Family Study Longitudinal study of two cohorts of twins – One recruited age 11 (1260 pairs), one age 17 (635 pairs) – Return basically every 3 years – IQ assessed (abbreviated WAIS/WISC) ages 11, 17, 25 in twins, intake in parents – Very population-representative; recruited from population records with ~80% participation, high retention over time

Correlations 11-yo17-yo Midparent-twins IQ At At At Twins' IQ over time Twins IQ by zygosity MZ at DZ at MZ at DZ at MZ at DZ at Midparent IQ-ed Midparent IQ-SES Midparent ed-SES Twins' IQ-midparent ed At At At Twins' IQ-SES At At At Mom-dad IQ

Another Correlation Higher parent’s IQ-absolute value of difference in parents’ IQs: –.515 in 11-yo –.605 in 17-yo Some examples: – , , , , , , , , , – 77-77, 78-78, 78-76, 79-77, 80-74, 81-75, 81-79, 82-76, 83-81, 83-73, 84-72, 84-83, 84-80, 85-72

Why? Above 100, higher up you are, fewer there are like you – But people with high IQ tend to be successful at what they’re doing and attractive partners to people in the more heavily populated lower parts of the distribution Low IQs are relatively rare too – But people in these ranges not so attractive to people in more heavily populated parts of the distribution – And less likely to participate in scientific studies

IQ and SES Gibson, J. B. (1973). Journal of Biosocial Science, 5, p. 254, Data from three Cambridge-based studies.

IQ and Earnings Murray, C. (1997). Public Interest, 28, p. 23. Data from NLSY.

Social Mobility? Murray, 1997

More Correlations

Socioeconomic status modifies heritability of IQ in young children Author(s): Turkheimer, E; Haley, A; Waldron, M; et al. Source: PSYCHOLOGICAL SCIENCE Volume: 14 Issue: 6 Pages: DOI: /j psci_1475.x Published: NOV 2003 Times Cited: 302 (from All Databases)302

Social Class, Solipsism, and Contextualism: How the Rich Are Different From the Poor Author(s): Kraus, MW (Kraus, Michael W.) 1 ; Piff, PK (Piff, Paul K.) 2 ; Mendoza-Denton, R (Mendoza-Denton, Rodolfo) 2 ; Rheinschmidt, ML (Rheinschmidt, Michelle L.) 2 ; Keltner, D (Keltner, Dacher) 2Kraus, MW 1Piff, PK 2Mendoza-Denton, R 2Rheinschmidt, ML 2Keltner, D 2 Source: PSYCHOLOGICAL REVIEW Volume: 119 Issue: 3 Pages: DOI: /a Published: JUL 2012 Times Cited: 0 (from Web of Science) Cited References: 234 [ view related records ] Citation Map 234view related records Abstract: Social class is shaped by an individual's material resources as well as perceptions of rank vis-a-vis others in society, and in this article, we examine how class influences behavior. Diminished resources and lower rank create contexts that constrain social outcomes for lower-class individuals and enhance contextualist tendencies that is, a focus on external, uncontrollable social forces and other individuals who influence one's life outcomes. In contrast, abundant resources and elevated rank create contexts that enhance the personal freedoms of upper-class individuals and give rise to solipsistic social cognitive tendencies that is, an individualistic focus on one's own internal states, goals, motivations, and emotions. Guided by this framework, we detail 9 hypotheses and relevant empirical evidence concerning how class-based contextualist and solipsistic tendencies shape the self, perceptions of the social environment, and relationships to other individuals. Novel predictions and implications for research in other socio-political contexts are considered. Intelligence Author(s): Sternberg, RJ (Sternberg, Robert J.)Sternberg, RJ Source: WILEY INTERDISCIPLINARY REVIEWS-COGNITIVE SCIENCE Volume: 3 Issue: 5 Pages: DOI: /wcs.1193 Published: SEP-OCT 2012 Times Cited: 0 (from Web of Science) Cited References: 72 [ view related records ] Citation Map 72view related records Abstract: Intelligence is the ability to learn from past experience and, in general, to adapt to, shape, and select environments. Aspects of intelligence are measured by standardized tests of intelligence. Average raw (number-correct) scores on such tests vary across the life span and also across generations, as well as across ethnic and socioeconomic groups. Intelligence can be understood in part in terms of the biology of the brainespecially with regard to the functioning in the prefrontal cortex. Measured values correlate with brain size, at least within humans. The heritability coefficient (ratio of genetic to phenotypic variation) is between 0.4 and 0.8. But genes always express themselves through environment. Heritability varies as a function of a number of factors, including socioeconomic status and range of environments. Racial-group differences in measured intelligence have been reported, but race is a socially constructed rather than biological variable. As a result, these differences are difficult to interpret. Different cultures have different conceptions of the nature of intelligence, and also require different skills in order to express intelligence in the environment.

100 Generations of Corn Breeding Hill, W. G. (2005). Science, 307, 683 – 684, adapted from Dudley, J. W., & Lambert, R. J. (2004). Plant Breeding Reviews, 24, Part 1, 79.