Two Men Shaking Hands
Credit: Harold M. Lambert/Getty Images

Shaking hands is one of the most common greetings, but have you ever stopped to wonder why we do it? We could nod or bow or simply smile or even do the hokey pokey, but instead we clasp hands and shake. Out of the context of our society, it's a seemingly odd choice.

While historians explain that shaking right hands became a friendly greeting, because it meant people came in peace and most likely weren't holding a weapon (at least not in their right hand). Science may offer another explanation, though—smell.

WATCH: The Scientific Reason Why Your Accent Gets Stronger When You Drink

While dog owners are used to seeing their pups take a good sniff of their new friends, humans don't typically exhibit the same behavior. Turns out we're just much more discreet about it. Researchers at the Weizmann Institute of Science used hidden cameras to observe more than 270 people sitting in waiting rooms. They discovered that after shaking hands with someone, a good portion of the population will subtly sniff their hands. It is completely unconscious, but it was still happening. You may find it hard to believe, but the video is pretty clear:

Before they were greeted by a member of the team, the research noted that the volunteers had their hands near their noses 22% of the time. According to New Scientist, after shaking hands with someone of the same sex, volunteers were filmed subtly sniffing their hand more than twice as much as they did before the handshake. The unconscious act is still subject to social mores, of course, so most of the sniffing was done when the experimenter had left the room and the volunteer was alone.

Since it's hard to know if someone is giving their hands a sniff, versus scratching their nose or rubbing their eyes, some of the volunteers were fitted with devices that measured the airflow to the nose and, yep, they were sniffing. Why would they be sniffing? The scientists think it has something to do with "chemosignalling" or signaling via scent. The project's researcher told New Scientist, "People constantly have a hand at their face, they are sniffing it, and they modify that behavior after shaking hands." The scientists believe that there is a lot more chemical communication going on among than we are aware of, at least among humans. The next time you shake hands with someone, watch where your hands go next because you just might be surprised.