A new study shows that men and women who inhale a whiff of the hormone oxytocin rate strangers as more attractive.
When oxytocin courses through our blood, "we are more likely to see people we don't know in a more positive light," says Angeliki Theodoridou, a psychologist at the University of Bristol, UK, who led the new study.
This effect adds to the hormone's known role in human relationships. One study found that oxytocin levels spike after new mothers look at or touch their newborns and may help bonding.
Other work has hinted at the importance of oxytocin in social situations between adults too.
People administered the hormone make overly generous offers in an economic game that measures trust, while men who got a dose of oxytocin proved better at remembering the faces of strangers a day later, compared to subjects who got a placebo.
In the latest trial, Theodoridou's team tested 96 men and women in a double-blind placebo-controlled trial. After participants got either a spritz of oxytocin or a placebo, they rated pictures of 48 men and women for attractiveness and 30 for trustworthiness. Her team also tested for mood.
No matter their sex or mood, volunteers who received oxytocin rated male and female strangers as both more attractive and trusting.
Theodoridou's study did not examine how oxytocin could affect social judgements, but she speculates that the hormone dampens brain activity in a region involved in processing fearful emotions, called the amygdala.
A previous study found that oxytocin tempered amygdala activation in volunteers who saw a face that had previously been paired with a slight shock.
Although Theodoridou's study shows that oxytocin acts similarly on men and women when rating strangers, sex differences could emerge in real-world situations, says Jennifer Bartz, a psychologist at Mount Sinai Medical School in New York. More research is needed to see if this is the case, she says.
Unsurprisingly, entrepreneurs are already trying to make a buck off of oxytocin's social effects. One company offers a spray that claims to engender trust in others, though it offers little more than testimonials as evidence that it works.
Could a similar spray spark romances between total strangers? Theodoridou doesn't think so. "I would not endorse any of these products," she says.