Mental rotation in female fraternal twins: Evidence for intra-uterine hormone transfer?
Martin Heil1, Michael Kavšek, Bettina Rolke
1Heinrich-Heine University, Düsseldorf, Germany. Martin.Heil@uni-duesseldorf.de
Abstract:
Men outperform women in mental rotation by about one standard deviation. Prenatal exposure to testosterone has been suggested as one cause. In animals it has been shown that a female fetus located between two male ones is exposed to higher levels of testosterone. It is still unclear whether intra-uterine hormone transfer exists in humans. Therefore, the influence of an intra-uterine presence of a male co twin was studied in female fraternal twins (N=200). Women with a male co-twin outperformed women with a female co-twin by about a third standard deviation. In a no-twin control group (N=200), performance of women with a slightly older sibling did not depend upon the sibling's sex. These findings provide preliminary support for the theory of an influence of prenatal testosterone on mental rotation performance.
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