A meta-analysis of twin studies on genetic & environmental influences on spatial reasoning: Spatial ability is highly heritable, genetic contribution of spatial ability varies by age group, do not vary by sex

Genetic and environmental influences on spatial reasoning: A meta-analysis of twin studies. Michael J. King et al. Intelligence, Volume 73, March–April 2019, Pages 65-77. https://doi.org/10.1016/j.intell.2019.01.001

Highlights
• Spatial ability is highly heritable (meta-analytic mean a2 = .61).
• Genetic contribution of spatial ability varies by age group.
• Contributions do not vary by sex.
• Contributions do not vary by type of spatial ability measure.

Abstract: 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  = .61; 95% CI [.55, .66]), with non-shared environmental factors having a substantial impact (meta-analytic . = .43; 95% CI [.38, .49]), and shared environmental factors having very little impact (meta-analytic . = .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).

Keywords: Spatial reasoningBehavioral geneticsMeta-analysisCognitive developmentIntelligence