Smell check: Why we shake hands

September 26, 2018

Everyone wants to get “a fair shake” from the hiring manager during a job interview. But, as it turns out, what you say during your encounter may not be as important as “what you do in a clutch” when you first meet. In fact, a Fortune 500 CEO once said that, when he had to choose between two job candidates with similar qualifications, he gave the position to the candidate with the better handshake.

So why is learning the art of a firm handshake so important in our society?  We could nod or bow— or simply smile or bump fists—but the handshake has been ingrained in our social discourse for, literally centuries. Supposedly, we started shaking hands during the Dark Ages, as a way to show the person we were meeting that we were not carrying a weapon and were “coming in peace.”

More recently, however, researchers have found another explanation. According to findings of a study conducted at Israel’s Weizmann Institute of Science, the reason we shake hands is to check out how the other person “smells.”

Just as our dogs and cats get a good whiff of each other during every encounter, humans also take a very subtle and discreet sniff.

Researchers at the Weizmann Institute 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 does happen.

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 a report on the study by New Scientist, after shaking hands with someone of the same sex, volunteers were filmed subtly smelling 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, yes, they were sniffing.

The scientists believe that our propensity to check out how other people smell has something to do with “chemosignalling” or signaling via scent.

To examine whether handshakes indeed transfer body odors, the researchers first had experimenters wearing gloves shake the subjects’ bare hands, then tested the glove for smell residues. They found that a handshake, alone, was sufficient for the transfer of several odors known to serve as meaningful chemical signals in mammals.

 “It’s well known that germs can be passed on through skin contact in handshakes, but we’ve shown that potential chemical messages, known as chemosignals, can be passed on in the same manner,” commented Idan Frumin, a Ph.D. student who assisted head researcher, Dr. Noam Sobel of Weismann’s Department of Neurobiology, in the investigation.

Research contact: noam.sobel@weizmann.ac.il

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