Human beings maintain the polite notion that we do not smell constantly. Despite our efforts to do the opposite, we all have our own odors, pleasant and less so, and if we are like other terrestrial mammals, our particular perfume can mean something to our fellows.
Some of them, such as the smell of someone who has not bathed for a month, or the distinctive breath of a small child who pretends not to have just filled his diaper, are self-evident. But scientists who study human sense of smell, or your sense of smell, wonder if the molecules that fly out of our skin can register on some subconscious level in the noses and brains of the people around us. Do they carry messages that we use in making decisions without realizing it? Can they even shape who we do and don’t like spending time around?
In fact, in a small study published Wednesday in the journal Science Advances, researchers examining pairs of friends whose friendships “clicked” from the start found intriguing evidence that everyone’s body odor is closer to that of their friend. than is expected by chance. And when researchers made strangers play together, their body odors predicted whether they felt they had a good relationship.
There are many factors that shape who people become friends with, including how, when or where we meet a new person. But perhaps one thing we understand, the researchers suggest, is how they smell.
Researchers who study friendship have found 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 Rareby, a graduate student in the laboratory of Noam Sobel, an olfactory researcher at the Weizmann Institute of Science in Israel, wondered if particularly fast friendships, of the kind that seem to form in an instant, have an olfactory component – whether people can see similarities in their smells.
The science of smell
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She attracted 20 pairs of so-called click friends, who both characterized their friendship in this way. She then put them through a regimen that is common in human body odor research: Stop eating foods such as onions and garlic that affect body odor for a few days. Discard after shaving and deodorant. Bathe with unscented soap provided by the laboratory. Then put on a fresh, clean T-shirt provided by the lab and sleep in it so that it becomes good and fragrant before handing it over to the scientists for examination.
Ms. Ravrebi and her colleagues used an electronic nose to assess the volatile substances rising from each T-shirt, and had 25 other volunteers assess the similarity of odors. They were interested to find that indeed the smells of friends were more similar to those of strangers. This may mean that the smell is one of the things they felt when their relationship began.
“It is very likely that at least some of them used perfumes when they met,” Ms. Ravrebi speculated. “But that didn’t hide what they had in common.”
However, there are many reasons for friends to smell the same – to eat in the same restaurants, to have a similar lifestyle, and so on – which makes it difficult to say whether the smell or the basis of the relationship came first. To investigate this, the researchers had 132 strangers, all of whom first sniff a T-shirt, enter the lab to play a game with a mirror. Pairs of subjects stood close together and had to mimic each other’s movements as they moved. They then filled out questionnaires to see if they felt connected to their partners.
The similarities of their scents, strikingly, predict whether they both believe there is a positive relationship 71 percent of the time. This finding suggests that smelling an odor similar to ours evokes good feelings. It can be one thing we understand 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 only one of many factors.
The Covid pandemic has so far limited further research using this design by Ms. Ravrebi and colleagues; experiments in which strangers get close enough to smell each other are difficult to organize.
But now the team is exploring how to change people’s body odors to see if subjects who have been made to smell in a similar way bond together. If the smell correlates with their behavior, this is further evidence that, like other terrestrial mammals, we can use our sense of smell to help us make decisions.
There are many mysteries about them and other researchers who need to explore how our personal scents, in all their complexity, interact with our personal lives. Each breath can say more than you know.
“If you think of a bouquet that is a body odor, that’s at least 6,000 molecules,” Dr. Sobel said. “There are 6,000 we already know about – probably many more.”
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