The natural scent of a woman at the peak of fertility (ovulation) triggers a surge in men’s testosterone levels, according to a new study, Health Cosmo reported.

This is the first study to show how men’s mating behavior may be affected by their sense of smell.

For the study, researchers conducted two separate experiments. One trial instructed men to smell T-shirts worn by women close to and far from ovulating (for three nights). The other directed the men to smell unworn T-shirts.

Prior to the tests, researchers collected saliva samples to measure the participants’ testosterone levels before and after smelling the shirts.

The results showed men preferred the smell of women close to ovulation. In addition, these men had higher testosterone levels than the men who smelled the T-shirts of non-ovulating women or the unworn shirts.

“Our results showed that men perceived women’s odors to be most pleasant right around the time of ovulation,” said researchers Saul L. Miller and Jon K. Maner of Florida State University in Psychological Science.

They also said the findings confirm that human mating behavior may be influenced by some of the same sensory triggers found among animals.