Speakers
Description
There is a broad consensus among the scientific community that human intelligence is affected by both nature and nurture components. However, researchers disagree on the strength of cognitive ability heritabilities with h² estimates ranging from the lower .20s to the upper .80s. Based on data of more than 30,000 mono- and 39,000 dizygotic twin-pairs from 20 different countries, we show in the present meta-analysis (77 studies, k = 328 effect sizes; 88 unique samples) that heritabilities for both intelligence and educational achievement-based assessments yield convergent summary effects, ranging between h² = .52 to .61 in bivariate and multilevel models. These estimates appear to be largely unaffected by potential confounders such as dissemination bias or decline effects, but are meaningfully associated with the Gini- and global social mobility index, suggesting larger heritabilities in more egalitarian societies. Moreover, our analyses reveal larger heritabilities of more strongly g-loaded intelligence measures. In all, our results indicate substantial intelligence heritabilities across different countries that appear to be stronger in more egalitarian countries.
