Common genetic and environmental effects on cognitive ability, conscientiousness, self-perceived abilities, and school performance

Personal characteristics (e.g., cognitive ability (CA), conscientiousness, self-perceived abilities (SPA)) predict differences in school performance. While genetic influences on CA and conscientiousness are unequivocal, origins of SPA have long been assumed to be environmental, however substantial genetic contributions have been detected in behavioral genetic analyses. In this study, we investigate the common etiology of these three predictors and their association with school grades in math and German as well as how genetic and environmental contributions differ between age groups and school domains. The sample consists of 2101 twin pairs (aged 11 and 17) and their siblings participating in the German TwinLife study. Using a multivariate twin-sibling design, we analyze common genetic and environmental effects on CA, conscientiousness, SPA and school grades in math and German in two age groups. Results confirm genetic effects for all three predictors (42-51% for CA, 31-42% for conscientiousness, 26-48% for SPA) as well as (non-) shared environmental effects. Multivariate analyses demonstrate that the interrelation between predictors and their association with grades is largely due to common genetic effects. Additional non-shared environmental effects and differences across age groups and school domains are small. We discuss possible underlying mechanisms and implications on individual differences in school performance leading to educational inequality.