Spatial ability and prenatal androgens: Meta-analyses of congenital adrenal hyperplasia and digit ratio (2D:4D) studies

Hormonal manipulations indicate that early androgens organize sex differences in spatial ability in laboratory rats. In humans, spatial ability is also sexually dimorphic, and information about the effects of prenatal androgens on spatial ability can be obtained from studies of congenital adrenal hyperplasia (CAH) and the ratio of the second and fourth finger lengths (2D:4D). CAH is characterized by prenatal overproduction of adrenal androgens and several lines of evidence suggest that 2D:4D reflects prenatal androgen exposure. Some studies have found that these proxy measures of prenatal androgens predict spatial ability, others have found no significant relationship, and yet others have obtained results in the opposite direction. In light of these mixed findings, we conducted meta-analyses of published literature and unpublished results to determine if, across studies, either of these indicators of prenatal androgens predicts performance on spatial tasks that show a male advantage. In addition, we applied a trim and fill analysis to the data in search of asymmetry that might be an indication of publication bias. Results indicated that females with CAH perform better on these spatial tasks, and CAH males perform worse, than do controls. Little or no relationship exists between 2D:4D and spatial ability. Implications for possible hormonal contributions and the developmental timing of sex differences in spatial cognition are discussed.