Businessmen, politicians and self-important college freshmen, take note: That firm-but-friendly handshake you’ve been perfecting over the course of your career — the one that’s supposed to say “I am a proper, professional person doing proper, professional things” — conveys more than you think it does.
Perhaps President Obama’s much-discussed fist bumps were the right way to go all along.
These revelations about the smelly scientific origins of handshakes were published by the Olfactory Lab at Israel’s Weizmann Institute of Science. There, researcher Idan Frumin and his team examined the handshake behavior of nearly 300 test subjects (who were not told that they were participating in a study on body odor). Researchers would come into the examination room and introduce themselves, some shaking the subject’s hand, some not.
Video footage from the study shows that subjects who had shaken hands would lift their hands to their noses to investigate the olfactory leftovers of the interaction almost as soon as the researcher left the room. Measurements of nasal airflow showed that participants inhaled through their noses twice as deeply when their hands were raised to their faces, indicating that they were indeed sniffing for odors exchanged during the handshake.
“Our findings suggest that people are not just passively exposed to socially-significant chemical signals, but actively seek them out,” Frumin said in an press release. “Rodents, dogs and other mammals commonly sniff themselves, and they sniff one another in social interactions, and it seems that in the course of evolution, humans have retained this practice — only on a subliminal level.”
To test whether these chemical messages, called chemosignals, could be transferred via handshake, Frumin had some of his researchers shake hands while wearing gloves. Tests of the glove material revealed residue of several chemosignals from the subjects’ bare hands — the same kinds of signals that have been observed on other mammals.
The purpose of the handshake may be biological, but that doesn’t mean that social dynamics weren’t at play. Frumin noticed that participants more than doubled the amount of time spent sniffing their right hand after shaking hands with a researcher of the same gender, while a handshake with someone of the opposite gender made them twice as likely to sniff their left (non-shaking) hand, while keeping their right (shaking) hand far away from their nose. The study didn’t propose an explanation for this phenomenon.
Frumin and his team manipulated gender dynamics in other ways as well. He had groups of researchers wear chemically tainted wristbands — one type bore male sexual hormones, another exuded female hormones — and a third group was sprayed with a unisex perfume. Fewer than half of the participants noticed the new smells, but almost all of them were effected by them. Participants who were exposed to the hormones were less likely to smell the hand they had shaken, but more likely to sniff its opposite. The perfume didn’t seem to have an effect on left- or right-hand sniffing — bad news for people who might want to cloak their chemosignals beneath a synthetic scent.
It’s important to note that the sniffing was subconscious, stemming from a deep-seated biological impulse rather than a bizarre desire to check out someone else’s body odor.
“Our findings suggest that at its evolutionary origins, handshaking might have also served to convey odor signals,” neuroscientist Noam Sobel, who oversaw Frumin’s project, said in the press release. “And such signaling may still be a meaningful, albeit subliminal, component of this custom.”
More from Morning Mix