Sexual Orientation, Sexual Arousal, and Finger Length Ratios in Women.

In general, women show physiological sexual arousal to both sexes. However, compared with heterosexual women, homosexual women are more aroused to their preferred sex, a pattern typically found in men. We hypothesized that homosexual women's male-typical arousal is due to their sex-atypical masculinization during prenatal development.

Patterns of Genital Sexual Arousal in Transgender Men.

Most men show genital sexual arousal to one preferred gender. Most women show genital arousal to both genders, regardless of their sexual preferences. There is limited knowledge of whether this difference is driven by biological sex or gender identity.

Correction to: Finger Length Ratios of Identical Twins with Discordant Sexual Orientations.

Readers should note that the confidence intervals for the effect of sexual orientation on 2D:4D in the left hand of female twins are incorrectly reported in Table 1 of this article. In particular, the upper limit of the confidence intervals is missing a minus sign.

Sexual Arousal Patterns of Identical Twins with Discordant Sexual Orientations.

Genetically identical twins can differ in their self-reported sexual orientations. However, whether the twins' subjective reports reflect valid differences in their sexual orientations is unknown. Measures of sexual orientation, which are free of the limitations of self-report, include genital arousal and pupil dilation while viewing sexual stimuli depicting men or women.

Finger Length Ratios of Identical Twins with Discordant Sexual Orientations.

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.

Gender nonconformity of identical twins with discordant sexual orientations: Evidence from childhood photographs.

Childhood gender nonconformity (femininity in males, masculinity in females) predicts a nonstraight (gay, lesbian, or bisexual) sexual orientation in adulthood. In previous work, nonstraight twins reported more childhood gender nonconformity than their genetically identical, but straight, cotwins. However, self-reports could be biased.