Next up, the women were randomly assigned to one of three “smeller” scenarios: they smelled either their partner’s T-shirt, a stranger’s T-shirt, or a clean T-shirt laundered with unscented detergent. The scientists didn’t reveal which shirts were which.
Following the smelling portion of the study, the women were asked to take part in a stressful, interview-style test in front of judges and cameras, which the researchers called the “anticipation phase.” It involved a mock job interview and a math portion where they had to count backwards in intervals of 17.
The researchers followed up by asking the women questions about their stress — for example, if they felt anxious, physically uncomfortable, or tense. They also took saliva samples that were used to measure levels of cortisol, a stress hormone. Finally, the women were allowed a “recovery phase” where they could relax and read magazines.
Ultimately, the study found that "the majority of women experienced a stress-reducing benefit during the anticipation and recovery phases due to smelling their partner’s T-shirts,” says the study’s lead author, Marlise Hofer, a graduate student in psychology at the University of British Columbia.
This isn't the first time that studies have found a link between scent and emotion. While the research on the relationship between scent and sexual attraction is mixed, the famous "T-shirt study," led by researcher Claus Wedekind, found that men and women can identify partners who are genetically compatible simply by sniffing their sweaty T-shirts. Other studies have even found that women are capable of sniffing out heightened testosterone levels in men.
The authors of this study found that sniffing your partner’s clothes may be even more calming when you know they belong to your partner, the author added. “We asked after, ‘Did you think you were smelling your partner's shirt?’ [In] women who knew they were smelling their partner’s scent, we did see a reduced cortisol benefit,” Hofer says.
While the findings, published in the Journal of Personality and Social Psychology, looked at how a man's scent affects his partner, there's no reason why smelling your girlfriend's shirt wouldn't defuse your own stress too, says Hofer.
“We’d expect to find similar results even if we’d done it the other way around," she says.