Our noses are excellent guides when it comes to discerning what other people are all about – their hormones, their fear levels, whether they are suitable mates.
And what better way to get a strong whiff of someone than after a handshake? During skin contact, we rub numerous chemicals on to each other's skin, leaving fresh chemical samples for smelling.
By looking at the way 280 people behaved after greeting each other either with or without a handshake, scientists at the Weizmann Institute of Science in Israel unveiled a tendency to position the hand near the nose if bare skin contact has taken place.
Using hidden cameras, they found that when there was no handshake or a handshake where one person wore a sterile glove, people kept their hand close to their nose around 22 per cent of the time. This increased by a large amount when people shook bare hands, indicating a subconscious desire to sniff each other out.
The volunteers were also fitted with nasal catheters to measure airflow, and when the shaken-hand was nearby the breathing rate tended to increase rapidly – backing up the theory that sniffing was going on.
Indeed, the findings, published in the journal eLife, could explain why the handshakes evolved in the first place – as a way to smell each other in a way that is not rude and obvious.
So what are we actually smelling? According to the team, two of the main chemicals exchanged during a meeting of hands are squaline and hexadecanoic acid – both chemicals dogs are searching for when they crudely approach each other in the park.
"It is well-known that we emit odours that influence the behaviour and perception of others but, unlike other mammals, we don't sample those odours from each other overtly," explained Professor Noam Sobel, lead researcher in the study.
"Instead, our experiments reveal handshakes as a discreet way to actively search for social chemosignals," he said.
How to hold your hand
We have been told multiple times that our handshakes must be firm, authoritative and matched with eye contact, but in reality this is only half the story, and there isn't much we can do about the other half – we smell how we smell.
"Handshaking is already known to convey a range of information depending on the duration of the gesture, its strength and the posture used," explained Professor 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."