Scent plays a powerful role in choosing friends

We often think our first impressions come from sight as we notice how someone looks, speaks, and moves. We focus on what we see and hear, but there’s another sense, always present, usually unnoticed, that might shape friendship more than we realize: smell.

Every day, we pass strangers, meet new colleagues, and shake hands at events. Some of those people feel immediately familiar, others strangely distant.

Sometimes we like someone without knowing why. Sometimes we’re put off without a clear reason. Could it be the scent they carry – not necessarily a strong perfume or cologne, but the subtle mixture of personal habits that lingers in the air?

That’s the question a group of researchers set out to answer. Their study, recently published in Scientific Reports, reveals how scent – specifically what they call “diplomatic odor” – can guide social preferences from the very first encounter.

Our scent signals future friends

Unlike natural body odor studied in past research, diplomatic odor reflects daily life. It includes perfumes, shampoos, laundry detergent, pets, food, and everything else that shapes how someone smells during a typical day.

Study lead author Jessica Gaby is an assistant professor of psychology at Middle Tennessee State University (MTSU).

“It’s not just perfume,” said Professor Gaby. “It’s your dietary choices. Are you a cat person or dog person? What laundry detergent do you use?”

The study focused on how diplomatic odor influences friendship potential – how likely we are to want to connect with someone. Unlike studies of romantic attraction, this work explored platonic connections, the ones that make up most of our daily social landscape.

Friendship shapes mental and physical health. It helps people navigate life. Knowing what influences our initial decisions about friends matters. And as the study found, scent plays a surprisingly strong role.

Odor influences first impressions

The researchers designed a multi-part speed-friending event involving 40 women. First, they photographed the participants and gave them clean cotton T-shirts to wear during daily activities for around 12 hours.

Participants were asked to keep their habits unchanged, other than avoiding smoking and alcohol. They were told to wear the same products to the event that they used while wearing the shirts.

Then came the real test. In a controlled but realistic environment – a busy room full of chatter – participants smelled the worn shirts before any in-person meetings.

They rated how likely they would be to want to hang out with the wearer, be friends, or avoid them. This pre-interaction sniff test set the baseline.

The results already showed personal preferences. What smelled friendly to one person didn’t appeal to another. And that individual taste held meaning throughout the study.

Scent helps predict new friends

Next came the live speed-friending part. Each participant had about ten four-minute conversations with different people.

They sat across small tables, introduced themselves, and chatted. After each brief conversation, they filled out forms judging their chat partner’s friendship potential – just as they had done earlier, based only on scent.

“People take a lot in when they’re meeting face to face. But scent, which people are registering at some level, though probably not consciously, forecasts whether you end up liking this person,” said Vivian Zayas, professor of psychology at Cornell University.

The findings were striking. The friendship ratings based on smell alone closely matched the in-person ratings after the short chats.

“If you think you might be friends with someone you haven’t met based on a tenth-of-a-second exposure to their photograph, you are also more likely to judge them as a potential friend based on the scent of their T-shirt,” Zayas said.

Sight, smell, and first impressions

The study also included a test based on quick glances at portraits – 100 milliseconds per image. Even these brief flashes gave participants enough information to form an impression.

Yet when the researchers compared smell-based ratings with those based on photos, smell turned out to be the better predictor of how people felt after meeting someone. Multilevel statistical models confirmed that diplomatic odor had a stronger and more consistent effect than visuals.

Portrait-based judgments did matter – but not as much. The live interaction scores were more closely tied to what people had sniffed than what they had seen.

Importantly, this connection held even after accounting for other variables like time worn or intensity of the scent. The results were clear: scent quietly shapes social judgments, and does so powerfully.

Interactions can change perception

What’s more fascinating is that smell didn’t only influence how people felt going into a conversation – it changed based on what happened in that conversation.

Participants repeated the sniff test after the live chats. This time, they judged the same T-shirts again. And their opinions had shifted.

“It makes sense to me that the way you smell impacts the way I judge you,” Gaby said. “But I was most surprised by the learning, by the shift in the second set of readings – one interaction and you’re like, hmmm, maybe not.”

If someone had a good chat, their shirt smelled better afterward. If the interaction was disappointing, the scent seemed worse. This pattern suggests our brains update scent-based associations rapidly, using emotional memory to reframe what we’ve already experienced.

Scents and social chemistry

One of the strongest themes in the study was individual preference. There wasn’t one universally liked or disliked smell. What appealed to one person might not appeal to another.

“Everybody showed they had a consistent signature of what they liked,” Zayas said. “And the consistency was not that in the group one person smelled really bad and one person smelled really good. No, it was idiosyncratic.”

This finding adds depth to how we think about social chemistry. It’s not just about shared interests or mutual friends – it might also be about shared scent spaces, shaped by laundry, pets, and food.

The scent of friends

This study stands out because it took place in a natural setting. Participants weren’t isolated in scentless rooms. The researchers wanted to test scent in the kind of environment where friendships really form – noisy, busy, filled with competing sensory input.

In this real-world context, diplomatic odor still played a major role. It was perceptible and meaningful, even surrounded by other cues like voice, appearance, and body language.

The researchers also emphasized that diplomatic odor carries social information of its own. Unlike pure body odor, diplomatic scent reflects lifestyle and culture. It’s shaped by choice. This means scent may serve as a kind of soft signal about who we are – and who we might connect with.

Friendships help people thrive. They affect mood, resilience, and long-term health. And yet, we rarely stop to think about what drives those first moments of liking or disliking someone.

This research shows that our sense of smell plays a role in those judgments. Not consciously, not obviously – but powerfully.

The study is published in the journal Scientific Reports. 

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