Is your type more like Arnold Schwarzenegger or Zac Efron? Better check the medicine cabinet before answering. Weirdly enough, taking oral hormonal contraceptives can alter the type of guys ladies are attracted to. According to a recent study, women who pop the pill tend to choose dudes with less classically “masculine-looking faces”Oral contraceptive use in women changes preferences for male facial masculinity and is associated with partner facial masculinity. Little AC, Burriss RP, Petrie M, Jones BC, Roberts SC. School of Natural Sciences, University of Stirling, Scotland, UK. Psychoneuroendocrinology. 2013 March 22.. So why do women on birth control choose men with more feminine features like wide eyes and full lips (we’re lookin’ at you, Leo)? The Scottish study suggests the answer involves hormones, face ratios, and evolution.

While birth control has some obvious benefits, like preventing pregnancy, it’s worth knowing that it can also alter sexual preferences. Keep reading to learn how hormonal pills can have some unexpected side effects.

What’s the Deal?

It’s not exactly news that ladies love pretty boys (Bieber Fever, anyone?), probably because male and female ideas of beauty aren’t all that differentA statistical model of facial attractiveness. Said CP, Todorov A. Psychology Department, New York University, New York, NY, USA. Psychological Science. 2011 September;22(9):1183-90.. But a group of Scottish researchers weren’t content with that conclusionOral contraceptive use in women changes preferences for male facial masculinity and is associated with partner facial masculinity. Little AC, Burriss RP, Petrie M, Jones BC, Roberts SC. School of Natural Sciences, University of Stirling, Scotland, UK. Psychoneuroendocrinology. 2013 March 22.. They wanted to know why women had the hots for specific male facial traits (and left other facial traits out in the cold).

To that end, the researchers ran two studies involving hormonal oral contraceptive pills and interactive computer graphic faces. Fifty-five heterosexual women looked at digital images of male faces; they were asked to manipulate the faces until they found the ideal face suited for a short-term relationship and the ideal face for a long-term relationship. Once they’d created their Ken-tastic Dream Man, 18 of the women went home with birth control pills and 37 participants kept their hormones au naturale. After three months, both groups of women returned and performed the same facial-attractiveness test. The researchers found that the women who had been on the pill since the last testing session were less into dudes with masculine faces (as determined by three ratios: cheekbone prominence, jaw height/lower face height, and face width/lower face height) than the women who were not taking oral contraceptives.

But let’s face it—even the shiniest, prettiest digital face doesn’t make most women’s hearts go pitter-patter. So the researchers took their experiment out of the lab and into real life. They found 85 heterosexual couples that met while the woman was taking birth control pills, and 85 male-female duos that first felt the sparks fly when the lady was not using hormonal contraception. Here’s where it gets science-fiction freaky—the researchers took photos of the men and digitally manipulated the images to look more or less masculine. Then online participants judged the original photos and manipulated photos on how “masculine” they were. The men whose paramours took birth control pills had more feminine faces than the men whose lady loves eschewed hormonal contraception.

Is it Legit?

You betcha! It’s so crazy it must be true. Although the study wasn’t huge in scale, it had a unique design. Researcher Anthony Little explains, “The sample size of our study is small (in fact the experimental group was only 18 women) [but] the test is still quite powerful because we tested the women twice, once on and once off the pill so that any change we observe can only be attributed to pill use.” And previous studies have found that oral contraception can affect the quality of relationships between men and women, as well as initial mate choiceRelationship satisfaction and outcome in women who meet their partner while using oral contraception. Roberts SC, Klapilova K, Little AC, Burriss RP, Jones BC, DeBruine LM, Petrie M, Havlicek J. School of Natural Sciences, University of Stirling, Stirling, UK. Proceedings of the Royal Society B: Biological Sciences. 2012 April 7;279(1732):1430-6.Does the contraceptive pill alter mate choice in humans? Alvergne A, Lummaa V. Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK. Trends in Ecology and Evolution. 2010 March;25(3):171-9..

What’s less certain is why. The researchers behind this latest study hypothesize that evolutionary preferences play a major role. Other research has found men with more masculine-looking faces are generally perceived as physically stronger but less niceSexual dimorphism and personality attributions of male faces. PIvonkova V, Rubesova A, Lindova J, Havlicek J. Department of Anthropology, Faculty of Humanities, Charles University, Prague, Czech Republic. Archives of Sexual Behavior. 2011 December;40(6):1137-43.. For a long-term partner, women tend to select men with more feminine faces because doll-faced dudes are associated with cooperative behavior. And here’s the surprising part—when taking oral birth control pills, women are hormonally similar to pregnant women. Thus, they’re probably not looking for strong genes (because they’ve already got the bun in the oven) but for a supportive, less aggressive partner to help them out with those tired feet and aching backs.

The Takeaway

So should we all dump our birth control pills and go after the macho men? Not so fast! Little explains, “Naturally, we are very cautious in interpreting our data. There may be positive and negative aspects to the use of any synthetic hormone and more research needs to be done to allow individuals to be informed of any potential effects either on physiology or behavior.” The study also didn’t explore how women respond to different hormonal birth control methods (pill, mini pill, patch, ring, etc.)—in fact, Little notes that it would be interesting to repeat the experiments with various specific hormones to further understand how synthetic hormones effect women’s preferences when looking for a mate.

Besides, there are hundreds (if not thousands) of factors that contribute to a successful, healthy relationship beyond initial attraction. For many women, the benefits of oral contraception may outweigh its drawbacks and limitations. (And really, is a babyfaced boyfriend really that bad?)

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