For those female readers out there: you know those days when you’re feeling great, you’ve dressed up for work (or school, or just because) and when you look in the mirror it seems you’ve been blessed with a “thin day”…besides being some of the best days of the month, it turns out our body might be sending a signal to the outside world to take notice before those other days of the month. Yep- our body might be gearing us to act and dress more attractive to show the opposite sex that we are at a high fertility stage of our cycle. Think of it as fertility “flair.”

When we look other primates, we can see the obvious signs of female fertility within their cycle. Stepping around the evolutionary debate for a moment, we as human females can’t run around in the same way (we can, we just might get arrested) and it’s more likely that we aren’t aware of our high fertility versus low fertility phases anyway unless we are tracking them already. We’ve all said that we’re more negatively emotional due to hormones, so it stands that we might also have some positive benefits due to hormones as well. Our hormones may influence how we dress on a particular day, thus we end up looking more attractive during a certain phase in our cycle.

Don’t get me wrong, women will make choices to dress nice and fashionable any day of the month. But the hormonal influence behind that conscious choice is weighted heavier during the high-fertility phase of our cycle. Recent research by Martie Haselton and colleagues looked at this very phenomenon. 30 women (blind to the hypothesis of the study) from a large college campus posed for two standing full-body digital photographs with their hands placed at their sides. One photograph was taken during the high fertility phase and the other at the low fertility phase (they determined this through urine testing and a daily diary). None of the women were on oral or other hormonal contraceptives around the time of the study. Next, they had volunteer judges (also blind to the hypothesis of the study) rate the photographs for attractiveness, more fashionable clothing, showing more skin, and other hints at this difference.

Sure enough (or else I wouldn’t be blogging about it) the researchers found that the women who were in a high fertility phase of their cycle were rated as more attractive, more fashionable or wearing nicer clothes, and showing more skin. Now this isn’t to say that the girls were wearing sweats in one photograph and a mini skirt in the other. Although women would reveal more, the overall affect wasn’t “sexier” but just more attractive; skirts, better clothes, more accessories, as well as more skin. These girls were going to and from school and were dressing more attractively to fit the occasion. The researchers purported that if these girls were photographed before going to a bar or club, they’d see differences to fit that occasion as well. Considering that the judges consistently viewed the high fertility photos as more attractive than the low fertility photos, the idea that random constraints (i.e., sleeping in late or the weather) or deliberate choices to dress up couldn’t explain the difference.

Regardless of the underlying motivation, or evolution, the results of this study show that women have obvious, observable changes in behavior (in the case dress) associated with ovulation. This may be the most overt non-verbal cue for opposite sex partners of a woman’s fertility.

Further Reading:

Haselton, M., Mortezaie, M., Pillsworth, E., Bleske-Rechek, A., & Frederick, D. (2007). Ovulatory shifts in human female ornamentation: Near ovulation, women dress to impress. Hormones and Behavior, 51 40-45.