Handshakes may have evolved to help us sniff each other out, Israeli scientists believe.
A new study by the Weizmann Institute of Science has found that after the traditional greeting, people tend unconsciously to sniff their own hands.
The behaviour could be a subtle way to pick up and sample chemical scent signals, according to the researchers.
Professor Noam Sobel, chairman of neurobiology at the Weizmann Institute, said: “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. Instead, our experiments reveal handshakes as a discreet way to actively search for social chemo-signals.”
During the study 280 people were greeted either with or without a handshake while being filmed with hidden cameras to see how many times they touched their face.
The team discovered that people constantly sniff their own hands after shaking, keeping a hand at their nose about 22% of the time.
Individuals greeted with a handshake significantly increased the amount of time they touched their faces with the right hand.
However, this only seemed to occur when someone was greeted by a person of the same gender.
Measurements of air flow through the nasal passages showed that it doubled when a hand was close to the nose – proving that the participants were actively sniffing.
Previous studies have suggested that human scent signals, or pheromones, could play a role in mate selection, conveying fear, altering brain activity and synchronising women’s menstrual cycles.