美国纽约和洛杉矶等地最近流行一种新的交友方式：闻睡衣，找朋友。

Sniff¹ your way to love? Singles who attend so-called pheromone（信息素） parties haven't ruled it out.

The get-togethers - which have been held in New York and Los Angeles and are planned for other cities - ask guests to submit a slept-in T-shirt that will be smelled by other participants.

Then, voila（瞧，可不是） ! You can pick your partner based on scent², or so the theory goes.

The parties started as an experiment in matchmaking by a California woman weary of online dating, but it turns out they also have a root in science. Researchers have shown that humans can use scent to sort out genetic³ combinations that could lead to weaker offspring.

At an art gallery in Los Angeles on a recent night, partygoers huddled⁴ around several tables covered with plastic freezer bags stuffed with shirts and an index card bearing a number. Once they found one they liked, a photographer snapped a picture of them holding the bag and projected it onto a wall so the shirt's rightful owner could step forward and meet his or her odor's admirer.

Judith Prays, a Web developer, said she came up with the idea for pheromone parties after she failed to find a match online. Prays said she'd date men for a month or so before things soured until she started seeing a man who wasn't what she was looking for and wound up in a two-year relationship.

What she remembered was his smell.

"Even when he smelled objectively bad, I thought he smelled really good," the 25-year-old said. "And so I thought, OK, maybe I should be dating based on smell?"

At first, it was an experiment. Prays invited 40 friends to a party in New York and asked them to sleep in a T-shirt for three nights, put it in a plastic bag and freeze it, then bring it to the party. Bags were coded with blue cards for men and pink for women and numbered so the shirts' owners could pinpoint⁵ their admirers.

The night was a hit, Prays said, adding that half a dozen couples hooked up and one pair formed a relationship. Since then, she has held similar parties in New York and Los Angeles and is planning others for Atlanta and San Francisco.

Research studies using similar T-shirt experiments have shown that whose smell a person prefers is dictated⁶ by a set of genes⁷ that influence our immune response - which researchers say is nature's way of preventing inbreeding（近亲交配） and preserving genetic adaptations developed over time.

"Humans can pick up this incredibly small chemical difference with their noses," said Martha McClintock, founder⁸ of the Institute for Mind and Biology at the University of Chicago. "It is like an initial screen."

In one such study, McClintock and her colleagues had participants sniff inside a covered box without knowing that in some cases they were smelling worn T-shirts. What they found was people preferred the odors of those who had different genetic makeups⁹ from their own, but not radically¹⁰ different.