Three Interesting and related articles about scent
Not too long a read but informative and
interesting.
Bel
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.
