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Finger Length Ratios of Identical Twins with Discordant Sexual Orientations

Watts, TM and Holmes, L and Raines, J and Orbell, S and Rieger, G (2018) 'Finger Length Ratios of Identical Twins with Discordant Sexual Orientations.' Archives of Sexual Behavior. ISSN 0004-0002

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Abstract

A proposed marker of prenatal androgen exposure is the ratio of the index finger to ring finger (2D:4D). Within each sex, this ratio may be lower for those who were exposed to higher levels of androgens and become attracted to women, as compared to those who were exposed to lower levels of androgens and become attracted to men. We examined these patterns in identical twins with discordant sexual orientations. Because these twins are genetically identical, differences in prenatal androgen exposure, as reflected in their different finger length ratios, might contribute to their discordance. For 18 female twin pairs, non-straight (bisexual or lesbian) twins had significantly lower, or more masculinized, 2D:4D ratios than their straight co-twins, but only in the left hand. For 14 male pairs, non-straight twins had, contrary to our prediction, more masculinized finger length ratios than straight co-twins, but this difference was not significant. A reanalysis of present and previous data (Hall & Love, 2003; Hiraishi, Sasaki, Shikishima, & Ando, 2012) suggested that these patterns were robust. Furthermore, males had more masculinized 2D:4D ratios than females. This sex difference did not vary by sexual orientation.

Item Type: Article
Divisions: Faculty of Science and Health > Psychology, Department of
Depositing User: Elements
Date Deposited: 20 Jul 2018 08:29
Last Modified: 20 Jul 2018 08:29
URI: http://repository.essex.ac.uk/id/eprint/22695

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