Women looking for that special someone might want to think twice before spritzing Chanel No. 5. A new study suggests that a woman's natural scent may be all she needs.
Recent research shows that a man's testosterone levels, which are linked with sexual interest, are significantly higher when they smell the shirt of a woman who is ovulating. These findings could lead to the development of new fragrances that mimic this effect, and answer basic questions about human biology.
"This is an issue that has been hotly debated: whether or not ovulation is concealed in human females," said Jon Maner, a co-author of the recent paper in Psychological Science. "In lots of other species, there are very obvious indicators, but it has long been assumed that human females didn't give off these cues."
Over the last 10 years, however, psychologists have found that ovulating women may behave differently, with a tendency to be more flirtatious, have sexual fantasies more frequently, and prefer hyper-masculine men.
In surveys, men report being more attracted to ovulating women. The new study builds on this research by measuring the response of men to a specific chemical cue.
The researchers performed two separate but related experiments. In the first scenario, the scientists gave four women plain, white T-shirts. The women wore the shirts over three days when they went to sleep. The researchers then collected the shirts in plastic bags, divided them up according to whether the woman was ovulating, and froze them.
In the second experiment, the scientists added an extra variable: fresh T-shirts that hadn't been worn by anyone.
T-shirts in hand, the scientists asked dozens of men to stick their noses into the bags. As the men sniffed the shirts, scientists sampled the participants' saliva, which was used to measure testosterone.
Men who smelled the shirts of ovulating women in the first experiment had, on average, testosterone levels that were 37 percent higher than the men who smelled the shirts of non-ovulating women.
For the second experiment, the testosterone levels of the men who smelled the T-shirts of ovulating women were, on average, 15 percent higher than men who sniffed the two other T-shirt samples.
Other studies have linked higher levels of testosterone with an increased in sexual arousal, said Maner. Whether a 37 percent or 15 percent difference in testosterone is enough to affect a man's behavior is unknown.
Another unknown is the whether a man could detect an ovulating women in a real-world situation, say a crowded bar. The two experiments were done under controlled laboratory conditions. Nevertheless, scientists say the experiments could have real world significance for potential love connections.
"The men were smelling T-shirts, not real women," said Maner. "We would expect that the odor coming from a woman will be stronger than from a T-shirt that was frozen."
Exactly how far the odor diffuses away from a woman remains to be seen. Scientists also haven't identified the specific chemical scents that stimulate increases in testosterone levels in men.
It's possible that men are directly detecting the higher levels of estrogen during ovulation, said Jim Roney, a scientist at the University of California, Santa Barbara. Equally possible is that men are sensing other chemicals that rise and fall depending on the amount of estrogen. Scientists just don't know.
Despite the remaining unknowns, the new research marks a milestone for smell scientists.
"This is one of the first papers to show (a change in testosterone) in response to a chemical stimulus," said Roney. "It's a new area of research."