After You Shake Someone’s Hand, See If They Do This Afterward

A handshake can be used to interpret a lot about a person, but there might be even more of an exchange of information going on than you realize, according to a recent study.

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The next time you shake someone's hand, see if they reach up and touch their face at some point shortly afterward. Scientists from the Weizmann Institute of Science in Israel found that some people are unconsciously sniffing subtle chemicals from the other person's hand.

The experiment, published in the journal eLife, involved 280 people who were greeted with or without a handshake. Hidden cameras filmed them to see how many people would touch their face. Video footage observed that people, in general, kept their hand at or near their nose 22 percent of the time. After a handshake with a person of the same gender though, the study participants touched their face even more often.

Taking it a step further, the researchers also outfitted participants with nasal catheters to see if the post-handshake face touching was in fact to actually take a whiff — and it was.

"After handshakes within gender, subjects increased sniffing of their own right shaking hand by more than 100 percent," the study authors wrote in the abstract. "In contrast, after handshakes across gender, subjects increased sniffing of their own left non-shaking hand by more than 100 percent. Tainting participants with unnoticed odors significantly altered the effects, thus verifying their olfactory nature."

"It is well-known that we emit odors that influence the behaviour and perception of others but, unlike other mammals, we don't sample those odors from each other overtly," Professor Noam Sobel, chair the neurobiology the institute, said in a statement. "Instead, our experiments reveal handshakes as a discreet way to actively search for social chemosignals."

Watch this video about the research:

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Front page image via Shutterstock.