We smell the human scent on our hands

You won't believe you're doing this, but you actually are. After shaking someone's hand, you'll raise your hand to your face and inhale deeply. The experiment was conducted by Noam Sobel and his colleagues at the Weizmann Institute of Science in Rechovot, Israel. This newly discovered behavior, observed through covert filming, suggests that humans use physiological odors to send signals just as other mammals do. Women's tears and sexual arousal There's evidence that the scent of women's tears lowers testosterone levels and mutes arousal in men, and that human sweat can emit fear. People don't normally sniff each other, so how can we exchange information through scent? Scientists' point of reference "Researchers turned their attention to one of the most common ways people touch: shaking hands. We started observing people and noticed that after greeting, the hand somehow inadvertently reaches the face," says Sobel. Filming the behavior To find out whether people actually smell their hands, his team surreptitiously filmed 153 volunteers. Some were hooked up to physiological devices that measured the airflow into their noses . They weren't aware, however, of the purpose. Volunteers were filmed greeting a team member, whether or not they shook their hand. Researchers recorded how often participants raised their hands to their noses and how long they held them there. Sniffing frequency Before the greeting, both men and women had their hands close to their noses an average of 22% of the time. The nasal airflow then doubled, suggesting they were actually smelling the scent of their hands. Same-sex and opposite-sex relationships After shaking hands with someone of the same sex, both men and women sniffed the shaken hand twice as long as they did before the handshake. When the person was of the opposite sex, they sniffed the other hand twice as long as before. Intuition might tell us that it's impossible, that we smell a hand shaken by someone of the same sex more. Sobel advises against this, arguing that there are plenty of cases where signaling occurs between people of the same sex. He cites, for example, when women's menstrual cycles synchronize. He also suggests that specific behaviors may depend on context.