The number of seconds the subjects spent sniffing their own right hand more than doubled after an experimenter greeted them with a handshake.
The findings were published in the journal eLife.
The study was led by Professor Noam Sobel of Weizmann Institute’s Neurobiology Department.
“Our findings suggest that people are not just passively exposed to socially-significant chemical signals, but actively seek them out,” said Idan Frumin, the research student who conducted the experiment.
“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,” Frumin added.
Researchers asked participants to wear gloves while shaking the subjects’ bare hands, then tested the glove for smell residues – allowing researchers to examine whether handshakes indeed transfer body odors.
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 chemo-signals, can be passed on in the same manner,” Frumin said.
Next, the scientists used covert cameras to film some 280 volunteers before and after they were greeted by an experimenter, who either shook their hand or didn’t – this was done to explore the potential role of handshakes in communicating odors.
The researchers found that after shaking hands with an experimenter of the same gender, subjects more than doubled the time they later spent sniffing their own right hand the shaking one.
In contrast, after shaking hands with an experimenter of the opposite gender, subjects increased the sniffing of their own left hand the non-shaking one.
“The sense of smell plays a particularly important role in interactions within gender, not only across gender as commonly assumed,” Frumin said.
The final tests confirmed the olfactory nature of the hand-sniffing behavior.