A strong jaw may not be what women want, as a study finds those on the pill prefer less 'manly' men.
Contrary to popular belief, a strong jaw and masculine looks may not be what all women want, a new study has revealed.
Women taking the contraceptive pill actually prefer men with more effeminate looks - a trait associated with faithfulness and stability.
Women using the birth control pill were found to rate men with less masculine faces higher in terms of attractiveness compared to non-users.
In couples who first met when the woman was on the pill, the male partners were less likely to have 'manly' faces than those who met when the woman was off the pill.
Millions of women use hormonal forms of contraception and some studies, including this one, indicate the Pill could affect partner preferences.
If supported, these findings could have important implications for how relationships are formed, reported Live Science.
The study, detailed on Saturday in the journal Psychoneuroendocrinology, compared the romantic preferences of straight women ages 18 to 24 who were taking oral contraception against those who were not.
Researchers showed the women composite images of young male and female faces, which could be manipulated to appear more or less masculine (based on features like cheekbone prominence, jaw height and face width).
The women were tested twice - once when none of them were taking the pill and again three months after some began using the pill.
When women were taking the pill, they preferred less masculine male faces (those with more narrow jawbones and more rounded faces, for instance) than before they started taking birth control, the results showed.
Some research suggests that a preference for masculine or feminine traits may be linked to genetic benefits for a couple's offspring, such as strong immune systems.
A few studies have even found that women prefer more masculine traits during the fertile phase of their menstrual cycle.
一项新研究揭示，和大众观念相反，不是所有女人都喜欢强壮的下巴和男性化的外表。
那些服用避孕药的女性实际上更喜欢长相阴柔的男子，这种长相特征让人联想到忠诚和稳定。
研究发现，相比那些没有服避孕药的女性，服用避孕药的女性认为长相不那么男性化的男子更有吸引力。
那些在女方服用避孕药期间初次相遇的夫妻，相比那些在女方不服避孕药期间相遇的夫妻，男方拥有男性化长相的可能性更低。
数百万女性采用激素避孕法，而包括这项研究在内的若干研究都表明，避孕药会影响女性对另一半的偏好。
据《生活科学》杂志报道，如果得到证实，那么这些研究结果将会对两性关系如何形成具有重要的寓意。
这一研究的详细报道周六发表在《精神神经内分泌学》期刊上，该研究将年龄在18岁到24岁之间、性取向正常、口服避孕药的女性和没有服避孕药的女性的感情偏好做了对比。
研究人员向这些女性展示了年轻男子和女子面部的合成图片，这些图片可以通过处理让其显得更男性化或不那么男性化（通过调节颧骨高度、颌骨高度和脸部宽度等面部特征）。
这些女性都经过了两次测试——第一次所有女性都没有服用避孕药，在一些女性开始服用避孕药三个月后又进行了第二次测试。
结果显示，当女性服用避孕药时，相比开始服用避孕药前，她们更青睐不那么男性化的男子长相（比如那些下巴较尖、脸较圆的面孔）。
一些研究显示，对男性化或女性化特征的偏好可能是为了优化下一代的基因，比如让下一代拥有更强壮的免疫系统。
一些研究甚至还发现，女性在月经排卵期更偏爱男性化的长相。