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Instant Friends Smell Alike

Social chemistry is smell chemistry, which explains why some hit it off fast.

Key points

  • Instant friendship may have to do with the smell generated by our immune systems.
  • We subconsciously choose friends who have a similar smell.
  • When seeking partners for romance and sex, we seek out some difference, but not entirely different genes.
Kate Mangostar/Freepik
Source: Kate Mangostar/Freepik

New research from Israel suggests an explanation for why some people instantly click as friends.

Smell plays a big role in the social interactions of other land mammals–notably dogs. We've all seen dogs sniff each other out before choosing to play. Generally, a dog can tell from a distance if another dog is an enemy by smell.

We humans pick up smells subconsciously, science suggests–both our own and others. In the new research, a team at the Weizmann Institute of Science recruited same-sex nonromantic pairs, people whose friendships formed very rapidly before they had a chance to figure out how much they had in common.

After collecting body odor samples, the team analyzed how similar the friendship pairs' samples were, compared to random pairings. In one experiment, the researchers used a machine called eNose that analyzes odors chemically. In another trial, the team used human volunteers and asked how similar the samples were.

Either way, the friendship pairs' samples were deemed more similar than the random pairs.

Next, the team recruited strangers to engage in nonverbal social interactions in pairs and afterward asked them if they thought a friendship was possible. Again, the strangers that eNose deemed to have a similar smell were more likely to feel friendly. Smell predicted friendly feelings with 71 percent accuracy.

Why might this be? It may all come down to our immune systems and the subtle odors they produce. When it comes to friendship, we choose similarity.

For a romantic partner, we want difference, but not too much

Online daters who complain that they can't make any decision until they experience in-person "chemistry" have more than a little science on their side.

In romance, smell may play a different role. Science suggests that young heterosexual women find single men to have more powerful body odor than partnered men and that men can smell when a woman is aroused. Differences attract when it comes to smell and sex, possibly to give a potential baby a chance at better health. The differences occur "in the sequence of more than 100 immune system genes known as the MHC, or major histocompatibility complex." However, heterosexual women don't choose men with the most differences in those genes, but somewhere in the middle.

Video and online dating are at a big disadvantage here, as we can't (yet) smell electronically. One new nonprofit service, Smell Dating, gives you a chance to smell swatches of dirty T-shirts from potential dates.

Heterosexual women, is there a man you really like but just don't want to date? You wish you did, but you don't? It's possible that women "friend-zone" men because of smell cues since we like similarities in friendship and differences in sexual partners. One study has found that if you end up in a monogamous relationship with a man whose MHC is much like yours, you will be less sexually interested in him and more likely to cheat.

The good news here is that our MHC patterns are very distinct–and no one MHC pattern will appeal to everyone. If you smelled Justin Bieber's or George Clooney's used T-shirt, you might not swoon.

According to Smell Dating, scent is a powerful source of useful information regardless of your gender or orientation (the service doesn't even ask you for that information). So if you're dating online, these are all good reasons to meet in person as soon as you feel it's safe. And if you're hoping to make new friends, look for in-person situations as well.

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