1078. Manly Sweat Makes Other Men More Cooperative

By Paul Gabrielsen, Science Now, May 31, 2013

Take a whiff, men. A chemical component of other guys' sweat makes men more cooperative and generous, new research says. The study is the first to show that this pheromone, called androstadienone, influences other men's behavior and reinforces the developing finding that humans are susceptible and responsive to these chemical signals.

Pheromones are everywhere in the animal world. Bugs in particular give off these chemicals to sound an alarm, identify a food source, or attract a mate. And smitten animals may indeed have "chemistry" together—pheromone signals are a subconscious part of their communication.

Scientists didn't know if humans played that game as well. But in the last 30 years, they've identified both male and female putative pheromones that are linked to mood and reproductive cycles. Some fragrancemakers have even incorporated them into their products, hoping to add an extra emotional punch to colognes and perfumes. Real-life pheromones don't smell so nice, however: The specialized glands that produce these chemical compounds are located near the armpit, where they mix with sweat. Previous investigations focused on the chemicals as sexual attractants—studying a male pheromone's effect on female mood and behavior, for example.

Turns out that women aren't the only ones susceptible to the power of male pheromones. Evolutionary biologist Markus Rantala of the University of Turku in Finland crafted an experiment in which 40 men in their mid-20s played a computer game in which two players decided how to share €10. One player offers a possible split, and the other decides whether to accept or reject it. Each participant took a turn making or deciding on offers.

Then they took a hefty whiff of either yeast (a control) or androstadienone, a suspected male pheromone present in sweat (which was also mixed with yeast to mask any perceptible odor), and played the game again.

The 20 men who sniffed the pheromone offered, on average, half a euro more than the control group (about €5), and accepted offers around half a euro lower (about €3), the researchers report this week in PLOS ONE. Rantala and colleague Paavo Huoviala monitored the men's hormone levels throughout the experiment and found, to their surprise, that men with higher testosterone levels were the most generous players after sniffing the pheromone. "I didn't know that this pheromone could interact with testosterone at all," Rantala says.

The researchers speculate that their finding may hearken back to a time when cooperation between males conferred a survival advantage. "[A]pparently such behaviour is considered attractive by the opposite sex," they write.

Rantala doesn't think that it's too far-fetched to see this pheromone used as an advertising gimmick. "They could spray a pheromone in a car, for example," he says. "People will feel happier in the car and will probably buy more readily."

Don't expect your teammates to be more generous in your next pick-up basketball game, though. Rantala used high concentrations of the pheromone in his experiments, anthropologist Jan Havlíček of Charles University in Prague, who was not involved in the research, writes in an e-mail to ScienceNOW. "We don't know whether we would be able to observe a similar effect with [the] use of more realistic concentrations." The power of pheromones depends on context as well, he adds. "It would be interesting to see whether production of androstadienone is affected by the outcome of an actual competition," he writes, "such as a sports match."