We Pick Friends Who Smell Like Us

Have you ever experienced that magical moment when you meet someone new and it feels like you’ve known them forever? Maybe it’s happened to you with a new classmate, a colleague, or even a stranger you encountered in an unexpected place — a pub restroom, perhaps? In those first moments of meeting them, there’s an inexplicable connection — an instant click. Conversations flow effortlessly, your vibes match immediately. There’s chemistry. It’s what we fondly refer to as a click friendship.

For years, scientists have been on a quest to unravel the mystery behind these instant connections: why do we click with some people instantly? What hidden cues lead to forming such bonds?  It turns out that we may not be all that different from our furry friends in this matter. You may have noticed the intricate ritual of sniffing and scent-sharing that occurs when two dogs meet for the first time; it’s a ceremony that decides whether to reposition into a friendly play pose or bark aggressively. It’s not just dogs though; most land mammals rely on olfactory information to assess potential friends and foes. Researchers at the Weizmann Institute wondered: Do humans also sniff each other subconsciously to decide whether they can be friends? In a study published in Science Advances, they showed that this may indeed be the case: people who smelled similar were more likely to hit it off than those who didn’t. Yes, you read that right — our noses might play a much bigger role in our friendships than we imagined.

Friends who instantly clicked smell similar

The scientists conducted this study on 20 non-romantic same-sex friend pairs who mutually described their first encounter as a click friendship. They collected the participants’ body scent-containing T-shirts and sampled them using an instrument called an electronic nose (eNose). An eNose is a smell-detecting device containing various metal oxide sensors capable of detecting different volatile chemicals. When exposed to a mixture of volatile molecules that make up a smell, the molecule-sensor interactions create a unique pattern of electrical signals, thereby allowing us to record a smell fingerprint of the sample. Using the eNose, the researchers discovered that click friends exhibited more chemical similarity in their body odors compared to random pairs. To confirm this, the scientists called on professional smellers — individuals with a heightened sense of smell. The smellers were given randomized pairs of scent-containing T-shirts and asked to rate their similarities. The smellers’ results were in agreement with the eNose: click friends indeed smelled more similar to each other than random pairs.

Body scent can predict whether strangers click with each other

These results raised a fundamental question: if friends smell more similar than random pairs, can we predict whether two strangers could hit it off based on body scent alone? To explore this, the researchers devised an experimental set up. They recruited strangers, engaged them in interactions to identify pairs that clicked and those that didn’t, and then analyzed their smells using the eNose. To determine whether an interaction clicked or not, the researchers used the Mirror Game, a tried and tested imitation exercise to study non-verbal interactions between people. The exercise is based on the principle that coordinated body movements often reflect relationship quality and outcome. In the study, two strangers were asked to stand face-to-face at a close distance so they could subconsciously smell each other, and try to mirror each other’s hand movements. Based on scores for synchrony and whether they mutually reported a click, the researchers identified click and non-click pairs. They then performed eNose analyses of all the participants’ body scents. To their surprise, they found that the strangers who reported clicking with each other had significantly more chemical similarity than the ones who did not click.  In other words, the eNose could predict with ~ 70 % accuracy which individuals would click from their body scents alone!

These findings shed light on an interesting facet of human behavior: just as we gravitate towards friends who bear visual similarity to ourselves, it seems that we are also naturally drawn to those who smell like us. Click friends smell similar, and strangers who smell similar are more likely to hit it off than those who don’t share scent similarity. So there’s indeed chemistry in social chemistry! It makes you wonder whether we also pick romantic partners based on scent similarity. Could we have gotten the old adage wrong — perhaps it’s not love at first sight but love at first sniff?