The Second to Fourth Digit Ratio (2D:4D) in a Japanese Twin Sample: Heritability, Prenatal Hormone Transfer, and Association with Sexual Orientation

@article{Hiraishi2012TheST,
  title={The Second to Fourth Digit Ratio (2D:4D) in a Japanese Twin Sample: Heritability, Prenatal Hormone Transfer, and Association with Sexual Orientation},
  author={Kai Hiraishi and Shoko Sasaki and Chizuru Shikishima and Juko Ando},
  journal={Archives of Sexual Behavior},
  year={2012},
  volume={41},
  pages={711-724}
}
The second to fourth digit ratio has been argued to reflect prenatal hormonal influences and is reportedly associated with various psychological and behavioral traits, such as sexual orientation, cognitive abilities, and personality. We examined genetic and environmental influences on the second to fourth digit ratio (2D:4D) using a Japanese twin sample (N = 300). The genetic analysis showed substantial additive genetic influences for both right and left hand 2D:4D. The rest of the variance was… 
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References

SHOWING 1-10 OF 48 REFERENCES
Digit Ratio (2D:4D) in Twins: Heritability Estimates and Evidence for a Masculinized Trait Expression in Women from opposite-Sex Pairs
TLDR
Investigation of the 2D:4D ratio of 44 men and 70 women from 36 identical and 21 fraternal twin pairs suggested that the trait is substantially heritable, consistent with a prediction from sex-hormone transfer theory.
Heritability of the Second to Fourth Digit Ratio (2d:4d): A Twin Study
TLDR
A substantial genetic contribution is suggested to the determination of this hormonally related skeletal ratio in women, which could be more influential than the effects of common prenatal environmental factors.
Brief communication: Familial resemblance in digit ratio (2D:4D).
TLDR
Familial resemblance in the second-to-fourth digit ratio (2D:4D), a proxy for prenatal androgen action, was studied in 1,260 individuals from 235 Austrian families and heritability estimates based on parent-child and full-sib dyad similarity indicated substantial genetic contributions to trait expression.
Multivariate Genetic Analyses of the 2D:4D Ratio: Examining the Effects of Hand and Measurement Technique in Data from 757 Twin Families
TLDR
Multivariate modeling of the left- and right-hand measurements revealed significant genetic and environmental covariation between hands, suggesting that X-linked effects (such as the previously identified association with the Androgen receptor) are likely to be small.
Genetic and Environmental Influences on 2D:4D Finger Length Ratios: A Study of Monozygotic and Dizygotic Male and Female Twins
TLDR
Biometric model-fitting analyses indicated significant additive genetic and nonshared environmental influences on digit ratios in twins, and suggest greater similarity between 2D:4D ratios in MZ relative to DZ twins that can be accounted for by genetic and nontraditional environmental factors.
Finger-Length Ratios in Female Monozygotic Twins Discordant for Sexual Orientation
TLDR
Differences in 2D:4D ratio suggest that MZ twins share virtually the same genes, and lower ratio in lesbians is a result of differences in prenatal environment.
Second to fourth digit ratio: ethnic differences and family size in English, Indian and South African populations
TLDR
Low values of 2D:4D were associated with large family size in men and the situation was less clear in women but on balance there was evidence to support a relationship between high values of two to fourth digit ratio and large family sizes.
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