Socioeconomic Status Modifies Heritability of IQ in Young Children

Abstract

Scores on the Wechsler Intelligence Scale for Children were analyzed in a sample of 7-year-old twins from the National Collaborative Perinatal Project. A substantial proportion of the twins were raised in families living near or below the poverty level. Biometric analyses were conducted using models allowing for components attributable to the additive effects of genotype, shared environment, and nonshared environment to interact with socioeconomic status (SES) measured as a continuous variable. Results demonstrate that the proportions of IQ variance attributable to genes and environment vary nonlinearly with SES. The models suggest that in impoverished families, 60% of the variance in IQ is accounted for by the shared environment, and the contribution of genes is close to zero; in affluent families, the result is almost exactly the reverse.

Differences in genetic and environmental influences on the human cerebral cortex associated with development during childhood and adolescence

“…It has been demonstrated that a large sample is necessary to detect C , and the present study may lack sufficient power. Studies of heritability of cognition have found that there is a gene 3 environment interaction such that shared environmental factors become more prominent relative to genetic factors as socioeconomic conditions worsen [Harden et al, 2007;Turkheimer et al, 2003]. The subjects in the current study came primarily from middle to high socioeconomic settings.…”

Socioeconomic background modulates cognition–achievement relationships in reading

“…Interestingly, however, several studies have shown that genetic factors are more strongly related to language development or IQ among children from higher SES families, whereas environmental factors are more strongly predictive of these cognitive abilities among children from lower SES backgrounds (Rowe, Jacobson, & van den Oord, 1999;Turkheimer, Haley, Waldron, D'Onofio, & Gottesman, 2003). This has been interpreted as suggesting that the genetic potential for learning is expressed more fully when children have plentiful resources (Rowe et al, 1999).…”

Plastic and immobile: Unequal intergenerational mobility by genetic sensitivity score within sibling pairs

“…With its wide-reaching implications for school quality, early environment, health, and opportunities for social and cultural capital development, among other things, parental income could matter far more for child outcomes than the sensitive genotypes included in this analysis. Alternatively, any potential impact of genotype in the full sample may only be swamped among young adults from low-income backgrounds (Guo and Stearns 2002;Turkheimer et al 2003), but that pattern could still account for the null interaction in the full sample. Because the full sample does not account for the non-random distribution of genes or environment, this study cannot identify what explains the different results.…”

“…Rather than determining one's financial standing or educational attainment, for example, the importance of the genes one inherits may depend on social context or environment (Guo and Stearns 2002;Turkheimer et al 2003). As Conley (2011b:231) describes it, "A gene for aggression lands you in prison if you are from the ghetto, but in the board room if you are manor born.…”