What are the reasons for shaking hands?

Why do we shake hands in greeting?

In order to then sniff the hand, scientists found

Occasionally, scientists solve everyday puzzles that we haven't even thought about. The result can be unexpected insights into human behavior. Such as the evidence published in Science last year that forcing people to do nothing is uncomfortable: test subjects in an empty room, without books, writing utensils and mobile phones, even prefer to give themselves painful electric shocks rather than endure boredom.

And now: why do we shake hands in greeting? One thinks it will have something to do with establishing physical closeness. The hypothesis that this demonstrates being unarmed is also circulating in science. Well, none of this may be wrong, but it is not the whole truth either, as a working group led by Idan Frumin and Noam Sobel from the Weizmann Institute in Israel has now found out in the magazine eLive.

What we actually do is: We take smell samples from our counterpart. The scientists observed that people often put a hand to their face after greeting someone. So they tested the impression experimentally by inviting test subjects under a pretext, then letting them wait a few minutes alone in a room before an experimenter came in and greeted them (with or without a handshake), and then had to wait a few more minutes. The whole time a video camera was running unnoticed. The minute after the greeting was then compared with the minute before the greeting: the time of the hand between the eyebrows and chin in the test subjects who were shaken hands minus the same time in the test subjects who were not shaken.

We humans fumble with our faces astonishingly a lot, as shown in a bizarre, entertaining video for the article. Mostly with the left hand. Well quantified, the main target of this fumble is the nose. And indeed: after shaking hands, the time that the hands spent on the face increased dramatically, to more than double. Whereby there was a strange effect of gender: If the experimenter and test subject, who had shaken hands, were of the same gender, then the test subject brought their right hand to the nose. If, on the other hand, the two were of different sex, then it was the left that had not come into contact with the other.

This does not mean that we really bring our hand to our nose for the purpose of smelling. It could simply be a gesture of embarrassment (although the test subjects were alone before and after the greeting, so there was no one in front of whom they could have been embarrassed). But the researchers were thorough and, in a further experiment, equipped subjects, again under pretense, with nasal catheters to measure the air flow through the nose. As soon as the test subjects put their hand to their face, the inhaled volume increased. In short, they sniffed her hand.

When shaking hands, the body's own fragrances are transmitted

Is there anything to smell like after a handshake? Is there. The researchers put on a nitrile glove to shake hands and determined the adhering compounds using a gas chromatograph. They found several substances that are considered social chemical signals. When shaking hands, the body's own fragrances are transferred from one hand to the other (something that I might not really want to know).

As a final proof that hand sniffing is really about odor perception and not about jumping behavior, the researchers scented the experimenters either with perfume or with a male or female in a further experiment (in which only women were tested with women) Chemosignal. The quantities were too small to be noticed by most of the test subjects, but the smell changed their hand-sniffing behavior: Instead of smelling after the greeting on the right hand, as would be "usual", they significantly preferred the sex pheromones, especially with the sex pheromones left.

We humans are actually considered microsmats, i.e. animals with a bad nose, for whom odor information does not play a major role. Nevertheless, it is now common knowledge that smell perception has a surprisingly strong influence on us: be it when choosing a partner, for which it is important whether you can "smell yourself", be it with the synchronization of the menstrual cycle. And four years ago, Noam Sobel's research group found that the (imperceptible) smell of women's tears dampens men's sexual appetite.

It is still unclear whether the odor sampling by handshake has a biological purpose. It is interesting that women and men mainly examine their own sexes olfactory. Many animals do the same. On the other hand, the fact that when we meet a member of the opposite sex we smell the untouched hand could be interpreted as using a safe benchmark, perhaps also as self-assurance. The study's authors say nothing about this.

Incidentally, if you object that not all parts of the world greet you with a handshake, consider how other cultures do it: with kisses on the cheek in the Mediterranean or rubbing the nose with the Eskimos and Maori. The nose is brought directly to the body of the other. Shaking hands, on the other hand, is the most distant and inconspicuous way of checking the other person's smell. That we do it anyway suggests that it is important. Whatever. (Konrad Lehmann)

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