Genetic and Environmental Influences on Cognition Across Development and Context

Abstract

Genes account for between approximately 50% and 70% of the variation in cognition at the population level. However, population-level estimates of heritability potentially mask marked subgroup differences. We review the body of empirical evidence indicating that (a) genetic influences on cognition increase from infancy to adulthood, and (b) genetic influences on cognition are maximized in more advantaged socioeconomic contexts (i.e., a Gene × Socioeconomic Status interaction). We discuss potential mechanisms underlying these effects, particularly transactional models of cognitive development. Transactional models predict that people in high-opportunity contexts actively evoke and select positive learning experiences on the basis of their genetic predispositions; these learning experiences, in turn, reciprocally influence cognition. The net result of this transactional process is increasing genetic influence with increasing age and increasing environmental opportunity.

Keywords: Gene × Environment interaction; behavior genetics; cognitive ability; cognitive development; intelligence.

Fig. 1

Proportion of variance in cognition as a function of age. Shading around each line represents the imprecision of the estimate (± 1 SE). The family environment, often termed the shared environment, represents environmental influences that make siblings raised in the same family more similar to one another. The unique environment, often termed the nonshared environment, represents environmental influences that differentiate siblings raised in the same family. Data were aggregated from published reports, based on 11 unique longitudinal twin and adoption samples (weighted by the precision of the individual estimates): the Colorado Adoption Project (Petrill et al., 2004), the Early Childhood Longitudinal Study—Birth Cohort (Tucker-Drob, Rhemtulla, Harden, Turkheimer, & Fask, 2011), the Longitudinal Twin Study (Bishop et al., 2003), the Louisville Twin Project (McArdle, 1986), the MacArthur Longitudinal Twin Study (Cherny et al., 2001), a Moscow community sample (Malykh, Zyrianova, & Kuravsky, 2003), the Netherlands Twin Registry (Hoekstra, Bartels, & Boomsma, 2007; Polderman et al., 2006; van Soelen et al., 2011), the Twins Early Development Study (Davis, Haworth, & Plomin, 2009), and the Western Reserve Reading Project (Hart, Petrill, Deater-Deckard, & Thompson, 2007). Articles were identified by searching abstracts in PsycINFO. From the search results, we included longitudinal studies with samples of siblings with varying degrees of genetic relatedness, complete cross-time and within-time sibling correlations (or parameters from behavioral genetic models producing expectations for these correlations), measurement using an objective cognition/intelligence test, and participants under age 19 at both baseline and at least one follow-up measurement occasion.

Fig. 2

Variance in mental ability as a function of SES in late infancy (age 2 years) (A). Data come from a nationally representative sample of American twins, 25% of whom lived below the poverty line (Tucker-Drob, Rhemtulla, Harden, Turkheimer, & Fask, 2011). Variance in cognitive aptitude as a function of parental income in adolescence (age 17 years) (B). Data come from a positively selected sample of adolescent twins who sat for the National Merit Scholarship Qualifying Test (Harden, Turkheimer, & Loehlin, 2007), very few of whom were likely to be living in poverty. Because a Gene × SES interaction was detected in this more positively selected sample, Harden et al. (2007) concluded that “genotype-by-environment interactions in cognitive development are not limited to severely disadvantaged environments, as has been previously suggested.” Shading around each line represents the imprecision of the estimate (± 1 SE). The family environment, often termed the shared environment, represents environmental influences that make siblings raised in the same family more similar to one another. The unique environment, often termed the nonshared environment, represents environmental influences that differentiate siblings raised in the same family.