Not too long a read but informative and

interesting.

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Women Can Smell a Man's Intentions



By Melinda Wenner, Special to LiveScience

posted: 09 January 2009 10:20 am

ET

It's not hard to

tell when a guy is "happy to see you."
The twinkle in his eye, his

swagger, that sexy smile — all are clear signs he's in the mood.



And, at least subconsciously, a woman can also tell by the scent of

his sweat, according to new research.



Scientists have long debated whether humans, like animals, use

chemical signals called pheromones to communicate sexual interest to potential mates. Problem is, the effects of

pheromones are thought to be subconscious — meaning that if we do communicate using them, we sure don't know it.

It's also hard to know what these pheromones might be and how we sense them, so researchers understand little about

them.

But if human

pheromones are going to be anywhere, they're going to be in sweat, right? Denise Chen, a psychologist at Rice

University in Houston, and her colleagues devised an experiment to compare how women respond to different forms of

male sweat — sweat produced in everyday situations versus that produced when a man is turned on.



The researchers

speculated that if humans do produce and respond to sweat pheromones, then a woman should respond to a guy's sexual

sweat differently than she does to his normal sweat.



Chen and her colleagues asked 20 heterosexual guys to stop wearing

deodorant and scented products for a few days. Then they told the men to put small pads in their armpits as they

watched pornographic videos and became aroused (the researchers confirmed, using electrodes, that the images did the

job). Later, the guys were asked to exchange those pads for fresh pads to collect the sweat they produced when they

weren't aroused.

Then

the researchers recruited 19 brave women to smell the men's pads while undergoing brain scans.



The investigators used

functional magnetic resonance imaging (fMRI), a technique that reveals the brain regions a person is using at any

given time — even if their brain activity is subconscious.



Sure enough, the women's brains responded very differently depending

on which sweat they sniffed. (And no, none of them passed out.) The sexual sweat, but not the normal sweat,

activated the right orbitofrontal cortex and the right fusiform cortex, brain areas that help us recognize emotions

and perceive things, respectively. Both regions are in the right hemisphere, which is generally involved in smell,

social response, and emotion.

The findings bolster the idea that humans do communicate via subconscious chemical signals, notes Chen in her

study, which was published in the Dec. 31 issue of the Journal of Neuroscience.

Our sexual intentions, in other words, may be a lot

clearer than we ever intended them to be. That crush you have on your co-worker? She may already know — at least

subconsciously.








The Sexy, Healthy Scent of a Man

By

Robert Roy Britt, LiveScience Senior Writer



posted: 04 November 2004 02:06 pm ET

How smells get to the brain. Credit: The Nobel

Foundation

How smells

get to the brain. Credit: The Nobel Foundation The scent of a man, at least among mice, can reveal the state of his

health and determine whether a female gets pregnant, a new study shows.

The research suggests that other animals, perhaps even

you, choose mates in part based on the strength of their immune systems.

Previous research had shown mice prefer to breed with

mates whose immune-system genes -- which produce chemicals that help the body fight invading cells -- are different

from their own. Such selective sex leads to healthier offspring.



The new study shows how the selection

occurs.

Researchers at

the University of Maryland examined molecules known as peptides that come from the immune system and end up in

urine. Each mouse's disease-fighting peptides are unique, like fingerprints. A female records and remembers the

scent of a mate's peptides using its vomeronasal organ, inside the nose.

"Exposure, during a critical period, to urine odor from

another male, will prevent embryo implantation, leading to loss of pregnancy, while exposure to the familiar odor

will not," said Frank Zufall of the university's School of Medicine.



Spiking the punch



"We can trick this odor memory and the outcome of the pregnancy-block

test by adding peptides to urine," Zufall told LiveScience. "In other words, we can switch an unfamiliar urine odor

to a familiar one (and vice versa) by spiking the urine with only a few peptides."

Other studies have shown that vomeronasal organs in

many animals detect pheromones and other molecules that pack information on sexual and social status. Pheromones

were first discovered in the 1950s to be sex attractants in insects.



"We believe that detection of [immune system] peptides via the nose

may be of general significance for social behaviors in all vertebrates," Zufall said.

The study was led by Trese Leinders-Zufall and will be

detailed in the Nov. 5 issue of the journal Science.



Picky, picky



Similar peptides exist in human immune systems. But our vomeronasal

organ has apparently been rendered defunct by evolution, many scientists believe, though there's some uncertainty

about this. In fact the question of how and whether scent affects a woman has been widely debated in recent years.



Since discovering

powerful sex pheremones in silkworms decades ago, scientists have been hot to learn whether humans could be

similarly stimulated. The investigation has proved frustrating.



"Compared to insects, whose behavior is stereotyped and highly

predictable, mammals are independent, ornery, complex creatures," notes writer Maya Pines of the Howard Hughes

Medical Institute.

Like

any animal, we humans are picky. And that provides a line of investigation.

Stinky T-shirts

In 1996, Claus Wedekind, a zoologist at Bern University

in Switzerland, conducted what's become known as the stinky T-shirt study. Wedekind had 44 men each wear a t-shirt

for two nights straight, then tested how women reacted to the smelly shirts.

Like mice, women preferred the scent of men whose

immune systems were unlike their own. If a man's immune system was similar, a woman tended to describe his T-shirt

as smelling like her father or brother.



Since then, companies have developed pheremone-based perfumes and

cologns, with promises of increased sexual attraction. Researchers don't agree on their effectiveness.



More research is needed

to figure out how and to what extent a woman's nose leads her to sex, and how adept she is at picking a healthy

partner.

"We cannot rule

out that other parts of the human nose are able to detect the peptides," Frank Zufall said. "We can now ask whether

these peptides are present in human secretions such as sweat and saliva, whether they can be detected by the human

nose, and if so, whether they have any influence on our own social behavior."






When a Woman Smells

Best

By Sara

Goudarzi, Special to LiveScience

posted: 18 January 2006 ET
The scent of a woman is more

attractive at certain times of the month, suggests a new study that had men sniffing women's armpit odor.



"We were interested

whether armpit odor changes across menstrual cycle," said study author Jan Havlieek of the Department of

Anthropology at Charles University, Prague. "To test this, we asked a group of women to wear cotton pads in their

armpits for 24 hours."

The women didn't wear perfumes, use deodorants, eat spicy or smelly foods, smoke, drink alcohol or use

hormonal contraceptives such as the pill. Body odor was collected during three phases: menstrual (at the beginning);

follicular (between the first day of menstruation and the onset of ovulation); and luteal (the fertile stage).



"The fresh pads were

subsequently rated for their attractiveness and intensity by a group of 42 men," Havlieek told LiveScience.



The most attractive

smells, men said, were from the time between the first day of menstruation and ovulation.



The cycle



The typically 28-day

menstrual cycle involves the physiological changes that occur in a woman to prepare for a possibility of pregnancy.

It is controlled by the reproductive hormone system.



A cycle is divided into four parts and starts on the first day of

menstruation, which is the shedding of tissue and blood from the womb. In the follicular phase, a dominant ovarian

follicle—which is a sack that contains the ova, or egg—grows, becoming ready to ovulate. The mature egg is then

released in the phase known as ovulation around day 12. The cycle ends with the fertile phase.



Although many men would

tell you they're always in the mood, Havlieek and colleagues discovered that men find odors during the follicular

phase the most attractive and least intense. On the other hand, the highest intensity smells, corresponding to the

lowest attractiveness for men, were found during the time of menstrual bleeding.

"Traditionally it's believed that ovulation in human

female is concealed and there are no changes in attractiveness across the cycle," Havlieek said.



The study is detailed

in the January issue of the journal Ethology.



Further sniffing



Two other studies by different research teams came to similar

conclusions. But those investigations used T-shirts for odor sampling, "making it difficult to pinpoint the source

of the smell," said Havlieek, whose team restricted sampling to armpits only.


Finally,

the attractiveness of women's faces also changes during the month.



Havlieek's team found that facial images of women in the follicular

phase—when the dominant ovarian follicle is getting ready to ovulate—are considered more attractive as compared to

images taken in the luteal or fertile phase of the cycle.



The researchers hope to find out which chemical compounds are

responsible for the odor changes across a woman's menstrual cycle.