Smells are known to be critical to animal mating habits: Animal studies have shown that male testosterone levels are influenced by odor signals emitted by females, particularly when they are ovulating (that is, when they are the most fertile). Psychological scientists Saul L. Miller and Jon K. Maner from Florida State University wanted to see if a similar response occurs in humans. In two studies, women wore tee shirts for 3 nights during various phases of their menstrual cycles. Male volunteers smelled one of the tee shirts that had been worn by a female participant. In addition, some of the male volunteers smelled control tee shirts that had not been worn by anyone. Saliva samples for testosterone analysis were collected before and after the men smelled the shirts.
Results revealed that men who smelled tee shirts of ovulating women subsequently had higher levels of testosterone than men who smelled tee shirts worn by non-ovulating women or men who smelled the control shirts. In addition, after smelling the shirts, the men rated the odors on pleasantness and rated the shirts worn by ovulating women as the most pleasant smelling.