The Laws of Attraction
Karl Grammer and Elizabeth Oberzaucher are leading the research on the human scent's influence on sexual attraction. They've found that when women are ovulating, they produce copulins, a scent that attracts men. The researchers believe when a man gets a whiff of copulins, his testosterone levels rise. As a result, he secretes androstenone, an odor that repels women who aren't ovulating. "Bars and nightclubs across the world are the battlefield for this invisible biochemical war," Oprah says.