Researchers have observed that, following a handshake with someone of the same sex, people increase the amount of time they spent touching their faces with their right hands. This was examined further in a study. These patterns appeared common. Furthermore, when their hands were in proximity to their faces, the handshake study participants had increased nasal airflow, suggesting they were smelling their hands. This smelling activity was often subconscious.
For the study, researchers used hidden cameras to film 280 people greeted with or without a handshake. Following the interaction, the researchers saw that all participants tended to keep a hand near their nose about 22 percent of the time, but those that had shaken hands increasingly kept their right hands near their faces. Then, fitting volunteers with nasal catheters to measure airflow, the researchers found that airflow through the nasal passages doubled when their hands were near their noses.
The researchers suggest that their findings indicate that people are not just passively exposed to socially significant chemical signals, but actively seek them out.
Discussing the study, study coauthor Noam Sobel, chair of neurobiology at Israel’s Weizmann Institute of Science, said in a research note: “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 chemosignals.”
Commenting on the findings, Charles Wysocki of the Monell Chemical Senses Center in Philadelphia told New Scientist magazine that the findings “fit with the general idea that there is a lot more chemical communication going on that we are unaware of.”
The results of the study have been published in the journal eLife. The article is titled “A social chemosignaling function for human handshaking.”
