Nice to smell you
Do you realize you sniffed your hand after that last handshake? Here's why.
Turns out shaking hands might be more than just proper etiquette. It's also a way humans glean information about one another.
People often smell their hand – usually unconsciously – after a handshake, according to research done by the Weizmann Institute in Israel. The reason is that odors transferred during the shake send meaningful chemical signals we analyze with our noses.
“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,” wrote Idan Frumin, the research student who conducted the study under the guidance of Professor Noam Sobel of Weizmann’s Neurobiology Department.
Researchers conducted various experiments to arrive at their conclusion. They first donned gloves and shook subjects’ bare hands and then tested the glove for smell residues. They found a handshake transferred odors that contained chemical messages, known as chemosignals.
Next, the researchers observed nearly 300 subjects before and after they were greeted by an experimenter, who either shook their hand or didn’t. The researchers found that the subjects who received handshakes spent considerable time sniffing their hand afterward. The amount of time was, unsurprisingly, divided along gender lines. When shaking hands with an experimenter of the same gender, subjects more than doubled the time they spent sniffing their shaking hand. But after shaking hands with an experimenter of the opposite gender, subjects increased the sniffing of their non-shaking hand.
The researchers were able to determine the olfactory nature of the hand sniffing through measurements of nasal airflow that showed 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.
All this is to say: Next time you see two dogs straining at the end of their leashes to sniff one another, don't be so judgmental, OK?
For more on the study, see the below video.
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