On average, the length of the index finger (digit 2) divided by the length of the ring finger (digit 4) on the right hand, is greater in women than in men. Converging evidence makes it clear that prenatal androgens affect the development of digit ratios in humans and so are likely responsible for this sex difference. Thus, differences in 2D:4D between groups within a sex may be due to average differences between those groups in prenatal androgen exposure. There have been many reports that lesbians, on average, have a smaller (more masculine) digit ratio than straight women, which has been confirmed by metaanalysis. These findings indicate that lesbians were, on average, exposed to greater prenatal androgen than straight women, which further indicates that greater levels of prenatal androgen predispose humans to be attracted to women in adulthood. Nevertheless, these results only apply to group differences between straight women and lesbians; digit ratios cannot be used to classify individual women as gay or straight.

中文翻译：

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通过玻璃杯，黑暗：人的手指比例不完美地反映了产前雄激素。

平均而言，女性的食指长度（数字2）除以右手无名指的长度（数字4），要比男性大。越来越多的证据清楚地表明，产前雄激素会影响人类手指比例的发展，因此很可能是造成这种性别差异的原因。因此，性别内各组之间2D：4D的差异可能是由于这些组之间产前雄激素暴露的平均差异所致。有许多报道指出，女同性恋者的平均手指比例比直女要小（男性化程度更高），这已经通过荟萃分析得到了证实。这些发现表明，与异性恋女性相比，平均而言，女同性恋者遭受的产前雄激素水平更高，这进一步表明，更高水平的产前雄激素容易使人被成年女性吸引。然而，这些结果仅适用于异性恋女性和女同性恋者之间的群体差异。数字比例不能用于将个别女性分为同性恋或异性恋。