Large Cross-National Differences in Gene × Socioeconomic Status Interaction on Intelligence

Abstract

A core hypothesis in developmental theory predicts that genetic influences on intelligence and academic achievement are suppressed under conditions of socioeconomic privation and more fully realized under conditions of socioeconomic advantage: a Gene × Childhood Socioeconomic Status (SES) interaction. Tests of this hypothesis have produced apparently inconsistent results. We performed a meta-analysis of tests of Gene × SES interaction on intelligence and academic-achievement test scores, allowing for stratification by nation (United States vs. non-United States), and we conducted rigorous tests for publication bias and between-studies heterogeneity. In U.S. studies, we found clear support for moderately sized Gene × SES effects. In studies from Western Europe and Australia, where social policies ensure more uniform access to high-quality education and health care, Gene × SES effects were zero or reversed.

Keywords: behavior genetics; intelligence; open data; socioeconomic status.

Fig. 1.

Variance in cognitive-test performance for the U.S. sample accounted for by genetic and environmental factors, graphed as a function of socioeconomic status (SES). Cognitive test scores were standardized to a z scale within each data set prior to model fitting. This plot is very close to (but not identical with) a plot in which the y-axis represents the instantaneous proportion of variance for each level of SES.

Fig. 2.

Funnel plot of effect-size estimates for the Gene × Socioeconomic Status interaction in the U.S. and non-U.S. samples. Each plotted point represents the standard error and effect-size estimate for a study included in the meta-analysis. The triangle-shaped regions indicate where 95% of the data points should lie if there is no (within-group) heterogeneity in population effect sizes. CI = confidence interval.