A new research study shows women are able to smell another woman who is about to have her ovulation. Just a whiff of scent is enough to stimulate another woman’s testosteron levels.

It’s well known that testosterone is linked to aggression and competitiveness,” says lead author Jon Maner, a Florida State University psychologist. “Based on our testosterone findings, one could speculate that women exposed to the scent of ovulation might become more antagonistic or competitive.

Prior research found that men’s testosterone levels are also sensitive to female ovulation. For example, in one of Maner’s earlier studies, men who interacted with a female research assistant became more risk-taking and flirtatious when the assistant was in the high fertility stage of her menstrual cycle.