Suzana Herculano-Houzel


Every social interaction – friendship, information exchange, buying and selling and even a simple request to a stranger for help with an address – involves an assessment of trust: how much can you believe the person in front of you? Of course, decisions about the trustworthiness of others involve complex social issues. But biology doesn’t stand aside. After all, social interactions are, first and foremost, exchanges between beings who have a very similar biology, subject to the influence of the same molecules. Like oxytocin, for example, which is produced by the brain but can reach it through the nose. 

Previously only a hormone associated with lactation and childbirth, oxytocin is now recognized as a substance whose pro-social functions already include the formation of emotional bonds between mothers and children and between lovers, sexual preference for a partner, and even trust in investors. In 2005, a study by the University of Zurich in Switzerland showed that three sprays of oxytocin in each nostril of young university students was enough to make them more likely to entrust all their money to bankers who would have full decision-making power over the amount to be returned to the investor. Unfortunately, spraying oxytocin up bankers’ noses didn’t make them pay more dividends to investors. It makes sense; deciding how much of the profits to share with the investor is not a matter of trust, since the banker is taking no risk in the transaction. Giving the brain oxytocin through the nose only makes a difference when the interaction is social, between real people, and involves trust.

Now for this: according to another study by the University of Zurich, a little oxytocin sprayed into the nose of couples about to start an argument reduces the production of cortisol, a hormone produced in response to the stress of a fight, and makes couples more likely to “open their hearts” during the tug-of-war – perhaps because it makes them trust their partner more, despite their woes. It wasn’t in the study, but a few hugs before an argument should have a similar effect: hugs are the natural – and much more pleasant – alternative to the bottle of oxytocin sold at the corner pharmacy.

Before you start thinking about hugging your next victim before arguing with them, there is one small catch. According to the study, dripping oxytocin up your nose doesn’t change anyone’s mind about the content of the argument. Unfortunately… or not!

Originally published in Folha de São Paulo on November, 2006.

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