http://www.charlotte.com/observer/natwor/docs/pheromones0828.htm

The Sniff of sex

Scientists find signs of human pheromones

Swedish study indicates odorless hormones may trigger brain response

By SHANKAR VEDANTAM Washington Post

Certain chemicals similar to the male and female sex hormones trigger
distinctive brain activity when sniffed by the opposite gender, providing
the strongest evidence yet for the existence of human pheromones,
scientists reported Monday.

Brain scans of two dozen volunteers in Sweden found that a part of the
brain involved in regulating sexual behavior lit up when women were exposed
to a substance similar to testosterone, while the same brain area in men
lit up when they were exposed to a substance similar to estrogen.

The research, which convincingly demonstrated that the effect of these
chemicals on the brain is not because of their odor, will be of interest to
romantics and pharmaceutical companies.

While human pheromones have long been embedded as real in the public
imagination, spawning a bustling market of perfumes and potions for suitors
seeking to turn on the opposite sex, scientists have long debated whether
they existed.

The new research suggests that at least some human behaviors may be
subliminally influenced by invisible chemicals with no obvious odors.

"It's great, it's very exciting and very interesting," said Noam Sobel, a
neuroscientist at the University of California at Berkeley who studies
pheromones.

No visual or auditory signal that he could think of, said Sobel, has ever
been known to produce so sharp a distinction between men and women. "Is it
proof that these are pheromones?" asked Sobel. "No, but it is another block
in the wall, and it is a block in the wall that closes up the hole."

While animal studies have shown that the part of the brain activated in the
new study - the hypothalamus - is associated with reflexive sexual
responses, it remains unclear whether humans necessarily respond in
similarly predictable ways.

"I'm leaving open the possibility that these and other compounds may be
human pheromones, but one should not walk away after reading this paper
(believing) that these two compounds are the (only) human pheromones, and
that one affects females and the other affects males," said Charles
Wysocki, a neuroscientist at the Monell Chemical Senses Center in
Philadelphia. "There's much, much more work that needs to be done."

Besides sex, pheromones are widely involved in regulating other behaviors.
Animals, for example, mark territory using pheromones. Scientists have also
found a specific piece of tissue in the nasal passageways of animals called
the vomeronasal organ, which is what they use to sense pheromones.