The nose knows: the sexual power of pheromones

by Daphne R. Howland

Bees have them. Birds have them. Even pigs have them. And so do humans. But pheromones seem to elicit a much different effect in the animal kingdom, regardless of what the saleperson behind the scent counter tells you.

Why do some people seem to exude sexuality? What about those substances known as pheromones added to aftershave or perfume that mysteriously make you more sexually attractive? Are there pheromones actually strong enough to overpower an undesirable personality or attitude?

You can buy substances purported to contain pheromones. With names like \"Raw\" and \"SexScent,\" they are supposed to \"work like a charm.\" Many of the companies that manufacture these products are run by scientists who ardently defend them. They cite studies proving that their pheromone-laced scents have a proven capacity to help humans become more sexually attracted to one another, or at least feel good about themselves and their sexuality. But other scientists say these studies are flawed and misleading.

"Since we don't know a lot about the science, there is always the opportunity for individuals to stake claims," says Charles J. Wysocki, Ph.D., of the Monell Chemical Senses Center at the University of Pennsylvania. "Until we learn more, it's basically a discussion based on belief rather than data."

But even the most cautious pheromone researchers believe that isolating human pheromones could have major consequences for areas like infertility, menopause and other reproductive health issues. Wysocki and his colleagues, for example, are in hot pursuit of what pheromone perfume makers say they already patented.

Part of the reason the opposing groups of scientists have trouble finding a middle ground is because those who claim they've isolated human pheromones are keeping the evidence close to their vests. (Some companies admit they use pig pheromones, which haven't been proven to work on humans.) Studies conducted on consumers who have used the perfumes or colognes show mixed results; some of the products appear to generate a psychological effect that actually has nothing to do with sexual attraction or confidence.

"There are human pheromones in my products," insists Winnifred Cutler, Ph.D., a scientist who co-authored a ground-breaking study on human pheromones more than a decade ago. She now runs the for-profit Athena Institute, which tests and markets pheromones that you can add to your own perfume or aftershave at home. In her earlier studies, Cutler worked with George Preti, Ph.D., a chemist who now works with Wysocki at the Monell Center and who is critical of Cutler's current work. But Cutler remains undaunted.

"George is an excellent chemist. But my work focuses on women's sexuality. When others claim human pheromones don't exist, they're admitting that they don't know what our formula is. Which I'm happy about, because it's proprietary," Cutler says.

Cutler's 1/6-ounce vials sell for $98.50 for the women's version and a dollar more for the men's. She guarantees nothing, although published testimonials suggest that a dash of her pheromones can help you become more attractive at singles bars, spice up sex within your marriage, and can even help boost sales and other work-related accomplishments. "I have figured out the formula for human pheromones, and it works," Cutler says. "It doesn't matter how many people don't understand it."

While there is mystery, debate and controversy about the existence and role of human pheromones, their role is much better understood in animals. Pheromones are used extensively to biologically control populations of insects, for example. And even the more complex body systems of mammals apparently use pheromones to influence reproduction and other functions.

In general, pheromones can be defined as chemicals that have a biological or behavioral effect in their own right, as opposed to scents that trigger responses because of a learned association such as the "Pavlov's dog" response.

Most animal's noses have an organ known as the vomeronasal organ, or VNO, which appears to detect pheromones and then signals the brain to release hormones or neurotransmitters accordingly. The function of the VNO differs from the olfactory or "scent" role of the nose. Rather than sending information about smells up to the brain, it responds to other chemical signals. When your dog is able to sniff and track you down, he is using his old-fashioned sense of smell; when he goes nutty around a female in heat, his VNO is taking signals from her pheromones. A VNO has been discovered in humans, although many scientists believe it's only vestigial because no one has been able to find any wiring to the brain.

Pheromones are grouped into three types: primer, secondary, and, possibly, signaling pheromones.

Primer pheromones- influence menstrual cycles or otherwise trigger the release of hormones. They require exposure and time.

Secondary pheromones- found mainly in insects and in some mammals. These are the controversial "sexual attractant" pheromones that companies are packaging for retail sale. They trigger certain behaviors--a classic example being the behavior of a male mammal when he is near a female in heat. Although these behaviors are well documented in the animal kingdom--and fantasized about in the human kingdom--there is some question as to whether this is a real effect in humans, since it is a function of the VNO. And as mentioned above, there is some question as to whether humans even have a functional VNO.

Signaling pheromones- Some scientists consider this type to be controversial because it's unclear whether they trigger effects because of chemical qualties or because of a learned association with smell. In humans, for example, many researchers believe that mothers who are able to recognize which of a series of identical shirts belong to their own infants' are responding to pheromones. But others believe the mothers have simply learned to recognize their infants' scents, even though they can't be detected by an "ordinary" nose.

Regardless of the claims of scientists like Cutler, David Berliner, Ph.D., and others who sell patented (secondary) pheromones, it is the primer effects that most scientists believe to be the major, if not the only, effects of pheromones in humans.

In a discovery a year ago that gave a boost to the study of human pheromones, Martha McClintock of the University of Chicago was able to establish that women's exposure to other women's pheromones could speed up or delay the onset of ovulation. Twenty years before, McClintock had published a paper on the phenomenon of women's menstrual cycles becoming synchronized in group living situations like college dorms. In her recent study, McClintock used underarm sweat from nine women collected at different times in their menstrual cycles.

The substances were swabbed under the noses of 20 other women. Compounds collected at earlier points in the ovulatory phase shortened the recipients' reproductive cycles; those collected at later points lengthened their cycles. The work followed years of studies on rats that enabled McClintock to develop sophisticated models that plugged up many holes in similar studies by other scientists.

"Martha's rat studies were mathematically sound and able to prove her point. And having done that, she redid her human study," says David Abbott, Ph.D., a researcher at the University of Wisconsin-Madison Primate Center, who studies similar behaviors in Brazilian marmoset monkeys. "Her study showed subtle but highly predictable effects on the onset and delaying of ovulation in women. It invigorated everybody around the world, and it could have very precise consequences on human physiology."

McClintock's study has been the most concrete evidence to date that human pheromones do indeed exist. (Other studies, like Cutler's and Preti's work in the mid-80s, are considered too flawed to be reliable.) However, her study showed primer effects--effects based on a hormonal mechanism--so scientists must still come to some consensus as to whether pheromones in humans directly influence behavior. It may be that all the behavioral responses actually result from a hormonal effect.

"Because of McClintock's latest work, you can make the link from pheromones to hormones in humans. And we can make the link from hormones to behavior," says James V. Kohl, a clinical lab scientist and author of The Scent of Eros. "But to say that pheromones affect behavior? You can't say that for humans. I don't think we'll ever be able to make that leap because of the complex number of factors involved in human sexual attraction."

For most scientists, McClintock's study finally answered the question of whether humans emit pheromones. Now, the chemical compounds must be isolated and tested. And the questions now shift to "how?" and "why?" pheromones are at work in humans.

"I'm sure the scent story is in its infancy," says Wisconsin's Abbott. "We'll find that scent affects more than just ovulation. Maybe moods, maybe even a 'sixth sense.' It's hard to do controlled experiments with people and isolate all the confounding factors, so I believe it's going to take a long, long time."