Genetic and environmental influences on spatial reasoning: A meta-analysis of twin studies

Behavioral genetic approaches, such as comparing monozygotic and dizygotic twins, are often used to evaluate the extent to which variations in human abilities are the result of genetic (heritable), shared environmental, and non-shared environmental factors. We conducted a meta-analysis on the twin study literature-comparing monozygotic and dizygotic twins-to provide clarity and a general consensus regarding the extent to which genetic and environmental factors contribute to variation in spatial ability. Consistent with previous work, we found that spatial ability is largely heritable (meta-analytic a (a) over bar = .61; 95% CI [.55, .66]), with non-shared environmental factors having a substantial impact (meta-analytic (e) over bar.= .43; 95% CI [.38, .49]), and shared environmental factors having very little impact (meta-analytic (c) over bar.= .07; 95% CI [.05, .10]). Moderator analyses were performed to establish if spatial ability type, sex, or age impacted the explanatory power of genetics or environmental factors. These effects did not differ significantly by sex or spatial ability type. However, the influence of shared environments did significantly differ depending on age. This result was driven by the youngest age group (ages 4-15) demonstrating relatively high amounts of shared environmental influence (c = .15, 95% CI [.10, .20]) compared with the other age groups (cs = .00-.07).