Birth control pills do not alter women’s preferences for masculine faces

A new study published in Evolution and Human Behavior provides evidence against the idea that hormonal contraceptives significantly alter women’s preferences for masculine or symmetric male faces. The researchers found no meaningful difference in facial preferences between women taking oral contraceptives and those on a placebo. The findings suggest that hormonal fluctuations may not drive the kind of shifts in attraction that many earlier studies have proposed.

For decades, researchers have examined whether heterosexual women’s attraction to physical traits in men varies across the menstrual cycle. Early studies suggested that women prefer more masculine features when they are most fertile and that this effect disappears when women use hormonal contraceptives. This body of work supported a popular idea in evolutionary psychology known as the “dual mating strategy” hypothesis.

According to this hypothesis, women may have evolved to prefer genetic quality cues, such as facial masculinity and symmetry, during fertile phases to increase the chance of producing healthy offspring. The same theory suggests that during non-fertile phases, preferences might shift toward traits that signal long-term investment, such as warmth or dependability.

This perspective built on research from the 1990s that reported cyclic variations in women’s responses to male body odors and facial features. Early findings indicated that women preferred the scent of more symmetrical men when conception was most likely. Later studies extended this idea to facial traits, claiming that women were more drawn to masculine facial features near ovulation. These findings were influential because they suggested a hormonal mechanism that could shape mate preferences and, by extension, mating strategies.

“This project actually began many years ago. I was a PhD student in anthropology at Harvard when Anna Dreber, then a visiting PhD student from the Stockholm School of Economics, told me about an experiment she planned to run to test whether birth control might affect economic preferences,” said study author Coren Apicella, who is now a professor of psychology at the University of Pennsylvania.

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“Anna has always been drawn to big, methodologically ambitious projects. I remember thinking, Wow—a placebo-controlled oral contraceptive trial? That’s the gold standard, and pretty much unheard of in my field. Around that time, there was an active debate in evolutionary psychology about whether hormonal contraceptives—and hormonal fluctuations more broadly—shape women’s attraction to men. I told Anna about it, and that’s how the idea was born.”

“For over two decades, the evidence has been mixed — all over the map — and we wanted to contribute to the literature in a meaningful way. And here we are with this paper, over a decade after our first conversations.”

The double-blind randomized controlled trial involved 340 heterosexual women between the ages of 18 and 35. Participants were randomly assigned to either a combined oral contraceptive or an identical-looking placebo. Neither the participants nor the researchers knew who was in which group. The study lasted three months. Facial preferences were measured at the start and at the end of the study.

Each participant viewed pairs of male composite faces that differed in either facial masculinity or facial symmetry. For masculinity, the faces were created by digitally manipulating composite male faces to appear more or less masculine. For symmetry, the same faces were adjusted so that the features on either side of the face were more or less symmetrical. Participants were asked to choose which face in each pair they found more attractive. By comparing these choices at baseline and after three months, the researchers could see whether oral contraceptive use produced any shifts in preference.

The hormonal profiles of the two groups diverged as expected. Women taking oral contraceptives showed lower levels of several reproductive hormones, including luteinizing hormone, follicle-stimulating hormone, testosterone, and estradiol. This confirmed that the treatment was effective. Despite these changes, the study found no statistically significant differences in how much participants preferred masculine or symmetric faces after three months. The estimated effects were small and not distinguishable from zero.

The researchers also explored whether menstrual cycle phase in the placebo group affected facial preferences. Participants returned for the follow-up session at different points in their cycles, allowing the researchers to compare women in the follicular, ovulatory, and luteal phases. Hormone levels were used to verify each woman’s phase.

No significant differences in facial preferences were found between these groups. Similarly, when the team examined correlations between hormone levels and facial preferences, the results showed no consistent associations. Only two out of 132 statistical tests reached conventional significance levels, a number that is roughly what would be expected by chance alone.

The results suggest that previous findings linking menstrual cycle phase or hormonal contraceptive use to shifts in facial preferences may not reflect robust effects. Earlier studies often relied on smaller sample sizes, self-reported menstrual cycle data, and flexible analytic strategies. Those factors tend to increase the risk of false positives and inflated effect sizes. In contrast, this study followed a pre-registered analysis plan and used objective hormonal measurements, which increases confidence in the reliability of its findings.

The researchers also discussed why earlier findings might not replicate. Statistical power is a key factor. Many past studies had small sample sizes, making it easier to detect apparent effects by chance. Some earlier research also lacked pre-registration, allowing researchers to make analytical decisions after seeing the data. This flexibility can unintentionally increase the likelihood of finding spurious results.

Additionally, the assumption that facial masculinity and symmetry reliably signal genetic quality has come under increasing scrutiny. Recent meta-analyses suggest that these traits may not strongly predict reproductive or mating success, which weakens the theoretical basis for expecting hormonal influences on preferences for these specific features.

“We examined the question in every way possible and found nothing,” Apicella told PsyPost. “We compared women taking oral contraceptives to those on a placebo, looked across different points in the menstrual cycle, and examined variation in hormone levels. Preferences for masculinity and symmetry just don’t seem to shift with hormones the way people have claimed.”

“If there’s an effect, it’s likely small. In other words, taking the pill probably doesn’t change the kinds of faces women find attractive in men. These findings also challenge some influential evolutionary hypotheses—like the ‘good genes’ and ‘dual mating strategy’ accounts—which rely on the idea that women’s mate preferences systematically shift with fertility.”

There are, however, limits to what this study can say. The researchers acknowledge that their results apply only to facial masculinity and symmetry. Other traits, such as body shape, scent, or behavioral cues, might still be influenced by hormonal fluctuations. In addition, while the study was well powered to detect moderate effects, it cannot rule out very small effects that fall below its detection threshold.

“We can’t rule out very small effects—our study wasn’t powered to detect those,” Apicella noted. “But, we’re confident that neither oral contraceptives nor hormonal fluctuations produce the kind of bigger shifts in mate preferences that people often talk about. In some ways, it’s not that surprising. Attraction is messy. The heart wants what it wants– just maybe not because of your estradiol levels.”

“Our results only apply to facial masculinity and symmetry. It’s possible that other behaviors or preferences are more sensitive to hormonal shifts. Indeed, there is some evidence that more general mate-related behaviors — things like sexual desire and motivation — may change with a woman’s cycle, but we did not look at that.”

The study, “Oral contraceptives and women’s preferences for facial masculinity and symmetry: Evidence from a double-blind randomized controlled trial,” was authored by Eva Ranehill, Niklas Zethraeus, Coren L. Apicella, Liselott Blomberg, Bo von Schoultz, Angelica Lindén Hirschberg, Magnus Johannesson, and Anna Dreber.