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Picture this: You’re sitting down, engrossed in a meal, when an unfamiliar person walks by. There’s something about them—Hair? Smile? Vibes?—that instantly draws you in and makes you want to strike up a friendship.
A new study suggests that it could be the scent they exude that attracts you to them. Not just the way their skin or hair smells, but the deodorant and shampoo they use, the foods they consume, even their laundry detergent.
Our sense of smell tends to operate below the level of conscious awareness, says Jessica Gaby, a psychology researcher at Middle Tennessee State University and an author of the study, so our responses to it are often hidden from us. “But at the same time, it’s inescapable,” she says. “You can’t fake it.”
Gaby and her colleagues, who were at Cornell University when the study was conducted, brought 40 women aged 18-30 together in a Cornell dining hall, a large, refurbished barn with café tables that doubles as a beer hall at night. The scent of popcorn, beer, and leftover dinner wafted over the room: The idea was to have a complex olfactory environment. The women all identified as heterosexual, so the researchers could focus on the type of attraction that might lead to friendship.
Our responses to scent are inescapable. “You can’t fake it.”
In the first phase of the study, the participants received cotton T-shirts and were instructed to wear them for 12 hours straight without altering their daily routines, and to keep notes about their activities. One participant used spray paint in an art project, another had sex, another said she spilled a small amount of black beans on her shirt. In the second phase of the study, the participants were instructed to view photographs of different individual women, some of whom they would later meet. They then each sniffed the worn T-shirts, then had four-minute meetings, speed-dating style, with the other individual women, then sniffed their T-shirts again. After each step, they judged their friendship potential with the other women on a scale of 1 to 7.
The researchers found that odor was a better predictor than a photograph for in-person social judgments: If woman A liked B’s smell initially, she was more likely to see friend potential following the face-to-face meeting as well. That brief in-person encounter also appeared to shape later changes in perception of the woman’s smell: The more they liked the other woman in person, the more they later liked the smell of her T-shirt, which suggests a learned response element. The findings were published in the journal Scientific Reports.
Humans use a wide diversity of cues to determine whether they want to become friends with someone, of course. But smell is one important one, Gaby says: Odor has been shown to influence how people perceive other social cues and each individual has a unique biological odor signature. “It doesn’t overshadow the other pieces,” she says. “Smell is giving complimentary information.”
Scent evaluations are intensely personal, Gaby adds. No two individuals experience an odor in exactly the same way, due to genetic differences as well as preferences shaped by personal experiences, and even the strength of one’s sensitivity to smell, which can be affected by environmental exposures, among other factors.
Valentina Parma, the assistant director of the Monell Chemical Senses Center in Philadelphia, calls the new paper a forward-thinking, methodologically thoughtful study that addresses a largely underexplored area of social cognition: the role that so-called diplomatic olfactory cues—the smells that are shaped by our perfumes, deodorant, shampoo, or laundry detergent, as well as dietary and lifestyle choices—play in shaping platonic friendships.
Parma’s work had shown previously that body odors retain their social communication power even when masked by other neutral scents like cedarwood oil in a lab setting. This study takes it a step further by incorporating diplomatic scents, which reflect the world we live in, she says. “In relationships, both biological signals and intentional self-presentation deserve careful consideration.”
People tend to undervalue the role scent plays in their everyday lives
“One of the study’s greatest strengths is its ecological realism,” she says. “Much of the existing body odor literature relies on un-fragranced body odors, which limits applicability to real-world scenarios. This work bridges that gap.”
Parma, who is not involved in the new work, notes that it is based on a relatively small and homogeneous sample of people, which the authors themselves also acknowledge. Some relevant questions remain open, she says, including how smells influence impressions over more extended time periods, and what mechanisms shape the connection between odor and social perception.
People tend to undervalue the role scent plays in their everyday lives, she adds. Humans are a highly visual species—visual information can seem to dominate our judgments and interactions. “However, smell, which often operates below the level of conscious awareness, can profoundly shape impressions, reactions, and behaviors, particularly in ambiguous scenarios,” Parma says.
Inbal Ravreby, a postdoctoral fellow at Cornell who was not involved in the study, says the study is highly relevant to daily life. While it was already known to the scientific community that scent can influence mate choice and that people perceive the body odor of their friends as more pleasant than random people do, she says the study shows us that the interaction with someone actually shapes the way we perceive their smell.
“It seems that there is a feedback loop here: The judgments of diplomatic body odor predict future interaction quality, or first impression when interacting, which in turn, predicts the perceived pleasantness of the diplomatic body odor,” she adds. “These two key findings are fundamental to our understanding of the influence of others’ smells on our social lives, and the influence of our social interactions on our olfactory perception.”
Gaby is interested in exploring whether the findings apply to men and the longevity of first impressions based on body odor. “There’s a potential for learning and for building associations with the body odor or another person,” she says.
Scent silently bolsters our experience of the world. “It’s not a primary signal, but it’s inescapable,” she says. “You could stop looking at somebody, but you can’t really stop smelling them, because you have to breathe.” 
Lead image: melitas / Shutterstock
