Human beings maintain polite fiction that we don’t constantly smell. Despite our efforts to the contrary, we all have our own smells, pleasant and less, and if we are like other terrestrial mammals, our particular perfume could mean something to our fellow human beings.
Some of them, like the smell of someone not bathing all month, or the characteristic smell of a small child pretending not only to have filled his diaper, are explained by whether same. But scientists who study human smell, or your sense of smell, wonder if the molecules coming out of our skin may be registering on a subconscious level in the noses and brains of the people around us. Are they carrying messages that we use in decisions without realizing it? Could they even be shaping who we do and who we don’t like to spend time with?
In fact, in a small study published Wednesday in the journal Science Advances, researchers investigating pairs of friends whose friendship “clicked” from the beginning found intriguing evidence that each person’s body odor was more close to that of his friend from what was expected by chance. And when researchers got couples of strangers to play a game together, their body odors predicted if they felt they had a good connection.
There are many factors that shape who people make friends with, such as how, when, or where we meet a new person. But maybe one thing we catch, the researchers suggest, is how they smell.
Scientists studying friendship have found that friends have more in common than strangers, not just things like age and hobbies, but also genetics, brain activity patterns, and appearance. Inbal Ravreby, a graduate student in the laboratory of Noam Sobel, an olfactory researcher at the Weizmann Institute of Science in Israel, was curious as to whether especially fast-paced friendships, of the kind that seem to form in an instant, they had an olfactory component: whether people might be picking up similarities in their smells.
The science of smell
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He recruited 20 pairs of so-called click friends, both of whom characterized their friendship in this way. He then subjected them to a regimen that is common in human body odor research: stop eating foods like onion and garlic, which affect body odor, for a few days. Leave the post-shave and deodorant. Bathe with a perfume-free soap provided by the lab. Then put on a cool, clean, lab-provided t-shirt and sleep on it so that it looks good and smells good, before handing it over to the scientists for review.
Ms. Ravreby and colleagues used an electronic nose to assess the volatile substances rising from each t-shirt, and also had 25 more volunteers assess the similarity of odors. They were interested in discovering that, indeed, the smells of friends were more similar to each other than those of strangers. This could mean that the smell was one of the things they caught when their relationship started.
“It is very likely that at least some of them used perfumes when they met,” Ms. Ravreby. “But he didn’t mask what they had in common.”
However, there are many reasons why friends may smell the same: eating in the same restaurants, having a similar lifestyle, etc., making it difficult to know if the smell or the basis of the relationship came first. To investigate, investigators made 132 strangers, all of whom first smelled a T-shirt, enter the lab to play a game of mirrors. The pairs of subjects were close to each other and had to imitate each other’s movements as they moved. They then filled out questionnaires about whether they felt a connection to their partners.
The similarities in their smells, surprisingly, predicted whether they both felt there had been a positive connection 71 percent of the time. This finding implies that smelling an odor similar to ours generates good sensations. It can be something we pick up on when we meet new people, along with things like where they grew up and whether they prefer science fiction or sports. But Dr. Sobel warns that if this is the case, it is just one factor among many.
The Covid pandemic has so far reduced further research with this design by Ms. Ravreby and colleagues; Experiments in which strangers get close enough to smell each other have been difficult to organize.
But now, the team is looking to modify people’s body odor to see if subjects who have similarly smelled come together. If smell correlates with their behavior, this is more evidence that, like other terrestrial mammals, we may be taking advantage of our sense of smell to help us make decisions.
There are many mysteries for them and other researchers to study about how our personal fragrances, in all their complexity, interact with our personal lives. Every puff of air can say more than you know.
“If you think about the bouquet that is body odor, it’s at least 6,000 molecules,” Dr. Sobel said. “There are already 6,000 we know; it’s probably a lot more.”