Sex in lieu of favours is a fast emerging practice on the US campus.
Sex in exchange for help in preparing for a test, laundry washing, tickets to a college football game, many things. Perhaps anything a girl would desire but can't afford.
The anecdotal evidence is now backed by a survey at the Michigan University. 27 percent of the men and 14 percent of the women respondents said they had had such mutually beneficial exchanges even when they weren't in a committed relationship. And it is not a one-way traffic either. Men too have been enticed, reports CNN.
Although they weren't hard up for resources, the students surveyed "recognized the value of this socio-economic currency system," says Daniel Kruger, research scientist at the University of Michigan School of Public Health, who published his findings in the April issue of "Evolutionary Psychology."
"It's more about getting what you want than getting what you need," he says.
The trend is catching up. Ask 27-year-old Stephanie Greson who works part-time in online marketing for a chocolate company in San Francisco.
She wangled a nerve-tingling stay deep in the Amazon forests from a guide.
"It was amazing," Gerson says of her adventure in 2000. "We built our homes out of palm leaves, I saw animals I'd never seen before, he taught me the medicinal properties of all the plants, we picked fruit off the trees, we swam with and ate piranhas. And, of course, we had sex ... for almost two weeks."
Gerson never felt sleazy or uncomfortable with her unspoken arrangement with the busboy.
"It was a good barter both ways," she says. "I got to stay in the jungle, and he got to have sex with a cute, young American girl."
Such trades aren't so unusual. Throughout history, humans have used their bodies to get what they want -- from ancient Egyptian ruler Cleopatra, who cemented her power through liaisons with Roman rulers Julius Caesar and Mark Antony, to the man and woman who were arrested at a Fort Wright, Kentucky, motel in late June for allegedly swapping sex for gasoline. Regardless of our motivation, scientists say we're hardwired to use our bodies as a bargaining chip.
"Women are turned on just by the simple idea of their guy getting off his ass and doing something for them," says Rocky Fino, author of "Will Cook for Sex: A Guy's Guide to Cooking."
It works both ways, he stresses.
Ben Corbett, a 39-year-old contractor from Boulder, Colorado, credits his tool belt with prompting the barrage of come-ons he fields from female clients -- most of them married -- on a regular basis.
"It starts with the flirting, and it just progresses," says Corbett, who has run a construction and remodeling business for 20 years. "They'll touch my hand, and there's all this physical contact. Or they'll run around in their pajamas."
"Once," he says, "I was painting the hallway right outside a client's bedroom, and she was lying on her bed like a girl at a slumber party with her legs up and her arms crossed and her head resting on them, asking me if I had a girlfriend.
"It's all about the fantasy of being taken by the rough-hewn construction guy," muses Corbett who, despite the temptation, has avoided getting sexually involved with his clientele for fear of jeopardizing his business.
Call it crass, sexist or gender stereotyping all you want, but there are thousands of years of biological programming at work here, says Dr. Chris Fariello, director of the Institute for Sex Therapy at the Council for Relationships, a nonprofit relationship-counseling group based in Philadelphia.
Plain and simple, a partner who provides more resources -- wealth, shelter, home repairs -- is seen as more attractive and stands to reap more sexual rewards.