What Does Your Handshake Say? Depends How Dirty Your Hands Are

A handshake tells a lot about who you are and there are a lot of social cues exchanged in the process. A study is looking at handshakes and finds an interesting connection to smell. You might have seen two dogs sniffing each other in an inappropriate location, but animals use their noses to learn about each other. Humans do that via handshakes -- think of the pleasantry as a form of socially acceptable sniff.

Scientists from the Weizmann Institute of Science in Israel wanted to see how handshakes convey other social cues. In the study, 280 participants either shook hands or did not when greeting another person. A hidden camera recorded what happened after the handshake and the researchers found that people are constantly touching their face and smelling their hands. Hand-sniffing occurred more after a handshake with someone from the same gender and participants and the study found that participants had their hands around their nose around 22 percent of the time. A test to measure nose airflow determined the behavior was a way to get a quick sniff.

"It is well-known that we emit odors that influence the behavior and perception of others, but unlike other mammals we don't sample those odors from each other overtly," Professor Noam Sobel, chair of neurobiology at the Weizmann Institute of Science, said in a statement.

It turns out there's a lot that can be exchanged between two people and a few seconds of interaction. Smells can be used to determine a person's health, emotional state and attraction, according to S. Craig Roberts, a psychologist from the University of Stirling. One reason to explain the increase in hand-sniffing after a handshake with someone of the same sex: It was seen as a way to scope out the competition. Sniffing habits could also change based on context and relationship status.

Based on handwashing studies, our hands are covered with lots of things we may find appalling -- including fecal matter. But that could be a good thing when it comes to sharing social cues. "We simply don’t get to do this until we enter an intimate sexual relationship. But because hands wander, they pick up these more intimate odors and make them accessible in a socially acceptable way," Stirling said.