Lead author Jon Maner, a Florida State University psychologist, told Discovery News that it could be speculated that women exposed to scent of ovulation may become more antagonistic or competitive.
Maner and co-author James McNulty measured at the levels of testosterone of women before and after they had taken a whiff of t-shirts previously worn by other women aged 18-21.
The latter group had worn the clothing when they were at high fertility - days 13, 14 and 15 of the menstrual cycle - and when they were at low fertility- days 20, 21 and 22.
Women who wore the t-shirt didn't engage in sexual activity, showered with unscented soap and shampoo, refrained from using perfumes or deodorants, didn't smoke, didn't eat odor-producing foods like garlic.
In the study, women exposed to the scent of high fertility females showed higher levels of testosterone and the smell of a low fertility woman caused testosterone levels in the sniffers to significantly drop.
The study has been published in the journal Evolution and Human Behavior.