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Love at first… smell? New research proves body odour can help humans tell friend from foe

Subconsciously, humans are sniffing themselves all the time. But did you know you might be sniffing out friendship too?
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New research suggests humans' body odour plays a large role in deciding friendships.

Have you ever met a friend that you just “clicked” with? Before you go convincing yourself it was fate, consider this: It could have been a similar brand of body odour that brought you together.

A new study by the Weizmann Institute of Science reveals that our noses play a large role in helping us form friendships, by finding us friends that smell like us. 

Over the course of six months, researchers surveyed 20 pairs of same-sex non-romantic friends whose friendships “clicked” or formed rapidly. The study defines “click friendship” as an instantaneous connection between two people prior to sharing any substantial information about one another. 

To determine the role of smell in these chemistry-fuelled interactions, the researchers began by harvesting the body odour of each participant using an electronic nose with 10 metal oxide sensors. Then, the odours were used in a series of human perception tests where participants were asked to sniff and rate the similarity of different pairs' body odours.

The results of these tests suggest that click friends have greater similarity in the way they smell than random strangers do.

In fact, from the body odour data collected, researchers were able to predict with 71 per cent accuracy which two individuals would have a positive social interaction.

“These results imply that, as the saying goes, there is chemistry in social chemistry,” Inbal Ravreby, co-author and graduate student in Weizmann’s Brain Sciences Department, said.

There are at least three possible explanations for why this is, the study states.

This similarity could be related to the root causes of friendship; it could be a consequence of long-term friendship with similar lifestyle factors, such as eating together; or, it could be related to an unknown, independent factor.

But why has no one ever told you this before? According to the study, it’s because humans are quick to disregard smell in social interactions, as part of a social taboo. Particularly in Western culture, social sniffing is done largely subconsciously despite its prominent role in human behaviour.

Forming friendships isn’t the only aspect of our lives that our nose has a say in. The study also notes that a man’s testosterone can lower after sniffing a woman’s tears, a woman’s cortisol levels can rise after sniffing body odour, and aggressive behaviour can be triggered or blocked by sniffing body odour. 

In fact, all sorts of emotions, from fear to happiness, can be inferred by humans through their sense of smell, the study says.

However, in reviewing the limitations of their study, the researchers note that the COVID-19 pandemic has led them to speculate about a shift in humans’ sniffing behaviour.

What used to be a tool to decipher friend from foe, is now often covered by a mask or purposefully inhibited. In recent years, people have strayed away from consciously inhaling while close to strangers for fear of becoming infected with COVID-19, the study states. 

Despite this, the researchers write that they expect this shift to be temporary because the role of our nose in social decision-making is too great to be permanently left behind. 

To summarize their findings, Noam Sobel, co-author and head of the Department of Neurology at the Weizmann Institute of Science, said in a press release that while humans are likely still more complex than our mammalian friends, the human nose still deserves a little more credit.

“This is not to say that we act like goats or shrews — humans likely rely on other, far more dominant cues in their social decision-making,” he said. 

“Nevertheless, our study’s results do suggest that our nose plays a bigger role than previously thought in our choice of friends.”