Tobias Wolfram & Damien Morris
Educational attainment (i.e., ultimate years of education completed) is a key variable in the behavioural sciences because of its effectiveness in predicting a wide variety of important life outcomes. Despite being a measure that can be calculated from a single questionnaire item (e.g., “what is the highest qualification you’ve obtained?”) educational attainment (EA) is one of the best predictors of occupational status and income1, longevity and health outcomes2, and the risk of receiving a criminal conviction3. The qualities needed to advance through the modern secondary and tertiary education system appear to be useful for navigating a wide variety of challenges that life throws at individuals in advanced industrial economies.
One of the most established findings in the social sciences is that EA tends to run in families—a result which has widely been interpreted as evidence of persistent inequality in environmental opportunity and the “social reproduction” of socioeconomic advantages4,5,6,7,8. However, as noted by Jencks and Tach “the size of the correlation between the economic status of parents and their children is not a good indicator of how close a society has come to equalising opportunity… In particular, we must separate the contributions of genes” (p.2-3)9. From the 1970 s twin studies began to show evidence that the variation in EA had a substantial genetic component10,11. Two studies published in the last decade have sought to summarise the results of the international twin literature that has accumulated since then: a meta-analysis by Branigan et al.12 and a mega-analysis by Silventoinen et al.13 (see Supplementary Note 1). Both studies converged on similar results, estimating mean heritability at 40%–43% and mean shared environmental influence at 31%–36%. These heritability estimates are low relative to other highly correlated cognitive outcomes such as adult general cognitive ability (60%–80%)14,15,16 or adolescent school grades ( ~ 60% at age 16)17. However, the estimates of shared environmental influence are especially conspicuous, being among the highest for any behavioural trait investigated in adults.