Palm scent: the science of smelling after a handshake

http://www.theguardian.com/science/2015/mar/03/palm-scent-the-science-of-smelling-after-a-handshake

Version 0 of 1.

A firm handshake has long been viewed as a hallmark of success in the business world, but scientists say that the scent of your hand could also play a part. A study has revealed that after shaking hands, people tend to unconsciously sniff their own right hand, which the authors believe could be a discreet way of picking up chemical signals about those around us.

Prof Noam Sobel, who led the work at the Weizmann Institute of Science in Israel, said: “Unlike rodents, cats and dogs, it isn’t socially acceptable to walk up and sniff each other. We think this is a way we’ve developed to collect this information in a subliminal fashion.”

The study did not assess what information we might be gleaning from the faint scent of another person’s hand, but Sobel speculates it could relate to social status, dominance or health.

The finding adds to a number of studies in recent years showing that we unconsciously take in social information from scents.

Previous work by Sobel indicated that the smell of a chemical contained in female tears makes men less sexually aroused, while other groups have shown that we literally “smell the fear” of those around us through chemicals released in sweat.

Prof Gün Semin, a psychologist at the University of Utrecht, said the latest findings prove we are not simply passive recipients of chemical cues, but actively seek them out. “They’ve shown it appears to be an evolutionary smell sampling process,” he said. “It’s like what dogs do when they sniff each other in the park. Dogs are just doing it more honestly.”

Semin believes that we take in the scent as a way to become more familiar with a person rather than necessarily as a way to glean social cues about a person’s dominance or health, however.

In the study, 280 participants were covertly filmed before and after being greeted by a researcher, either with or without a handshake. The researchers observed that participants spent around 20% of the time with a hand near their nose, even before the handshake had taken place. “They were constantly bringing their hand to their face,” said Sobel. “It was overwhelming.”

In the minutes following a handshake with someone of the same gender, participants more than doubled the amount of time they spent with their right hand near their nose.

Intriguingly, after shaking the hand of the opposite sex, there was no increase in right hand sniffing, but people more than doubled the amount of time spent sniffing their left (non-shaking) hand, which the authors said could be “some sort of reassurance mechanism”.

Craig Roberts, a psychologist at the University of Stirling, said: “The importance of social smells in human behaviour is under-appreciated and this study reveals how we are subconsciously interested in other people’s odour.”

He said it was puzzling, however, that people are apparently less interested in smelling the opposite sex, since most studies to date have linked social smell perception with assessing possible partners.

In a follow-up experiment, a second group of participants were fitted with nasal catheters to check that they were actually smelling their hands rather than just itching their noses or inspecting their nails. People were shown to reliably sniff when their hands were near their nose.

“Handshaking is already known to convey a range of information depending on the duration of the gesture, its strength and the posture used,” said Sobel. “We argue that it may have evolved to serve as one of a number of ways to sample social chemicals from each other, and that it still serves this purpose in a meaningful albeit subliminal way.”

The researchers also tested what chemicals are transferred by making handshakes while wearing sterile gloves and identified two chemicals, squalene and hexadecanoic acid (also known as palmitic acid), which are known to play a part in social signalling in dogs and rats.

Although handshakes are a staple of the boardroom, the authors say the practice is very ancient and fairly universal across cultures.

The study is published in the online journal, eLife.