Do we choose friends that smell like us? Science thinks there’s something to it

We maintain the belief that we do not constantly smell ourselves. Despite our efforts to the contrary, we all have our own scents, pleasant and less pleasant, and if we’re like other land mammals, our particular perfume might mean something to our fellow humans. According to one study, each person’s body odor was more similar to their friend’s than would be expected by chance.

Before obtaining these answers, the question of how odors can influence people was widely studied. The scientists who study the human smell wondered if molecules shedding from our skin may be registering at a subconscious level in people’s noses and brains around us. Are they carriers of messages that we use to make decisions without realizing it? Could they even be shaping people we like or don’t like to spend time with?

In this study, published in the journal Science Advances, researchers who studied pairs of friends whose relationship “clicked” early on found intriguing evidence that each person’s body odor was more like their friend’s than expected by chance. And when the researchers had pairs of strangers play together, their body odors predicted whether they felt they had a good connection.

Many factors determine who we become friends with, including how, when, or where we meet a new person. But the researchers suggest that one of the things we pick up is their scent. Scientists studying friendship discovered that friends have more in common than strangers: not just things like age and hobbies, but also genetics, patterns of brain activity, and appearance.

Inbal Ravreby, a graduate student in the lab of Noam Sobel, an olfaction researcher at Israel’s Weizmann Institute of Science, was curious whether especially quick friendships, the ones that seem to form in an instant, had an olfactory component. That is, if people could pick up the similarities in their scents. Ravreby recruited 20 couples of so-called “click friends,” who characterized their friendship in this way. Next, he put them through a regimen common in human body odor research that involves not eating foods like onions and garlic for a few days; stop using lotion, after shave, and deodorant; and bathing with a non-scented soap provided by the laboratory.

Later, the participants were instructed to wear a fresh, clean T-shirt provided by the lab, and sleep in it to transfer their smell to the shirt before giving it to the scientists for inspection. Ravreby and his colleagues used an electronic nose to assess the volatiles coming off each T-shirt and had 25 other volunteers assess the similarity of odors as well. He was interested in verifying that, indeed, the odors of friends were more similar to each other than those of strangers. That could mean that the smell was one of the things they picked up when they started their relationship.

“It is very likely that at least some of them used perfume when they met,” the expert speculated. And she added: “But that didn’t mask what they had in common.” However, there are many reasons friends might smell alike — eating at the same restaurants, having a similar lifestyle, etc. — making it hard to tell if the scent or the basis of the relationship came first. To test this, the researchers brought 132 strangers into the lab, all of whom first smelled a T-shirt. Pairs of subjects were placed close to each other and had to mimic each other’s movements as they moved. Afterward, they filled out questionnaires about whether they felt a connection with their peers.

Surprisingly, their scent similarities predicted whether they both felt there had been a positive connection 71% of the time. This finding implies that smelling a scent similar to ours generates good feelings. It can be one of the things we notice when we meet new people, along with things like where they grew up and whether they prefer science fiction or sports. But Sobel warns that if this is the case, it is just one factor among many others.

The COVID-19 pandemic has so far prevented Ravreby and his colleagues from further research with this design; experiments in which strangers get close enough to smell each other have been difficult to set up. But now, the team is studying the possibility of modifying people’s body odor to see if subjects who have been made to smell similarly clump together. If scent correlates with behavior, it’s further evidence that, like other land mammals, we can draw on our sense of smell to help us make decisions.

They and other researchers have many mysteries left to study about how our personal fragrances, in all their complexity, interact with personal lives. Each breath of air can say more than you think. “If we think of the bouquet that is body odor, there are at least 6,000 molecules. There are 6,000 that we already know about; there are probably many more”, concluded Sobel.

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