Chemical Signals: How You are Subconsciously Influenced by Other People's Sweat and Chemical Signals
Chemical signals that we humans cannot see, smell, taste
or hear are constantly at play in our environment, but researchers
are just beginning to skim the edges of this oceanic topic.
In animals, the topic is much more clear-cut. It's known
that animals secrete pheromones, chemical substances that
can communicate gender or reproductive status. Even sea urchins,
for example, give off pheromones into the water around them
that trigger other nearby urchins to simultaneously eject
their sex cells.
Are you attracted to your co-worker because of his
or her charm and wit, or is it really their chemical
signals you find irresistible?
In humans, pheromones, and how they affect us, is a controversial
topic -- more on this below -- but there is emerging new evidence
to show that pheromones are not the only chemicals at work.
Chemicals from those around us may be influencing you as you
read this -- and more than you think.
Fear-Induced Sweat Heightens Awareness
A study on 75 women, published in the journal Chemical Senses,
found that sniffing someone else's fear-induced sweat may
make you more alert and even more intelligent. Each woman
had a piece of gauze that either contained nothing or contained
sweat from people's armpits who had been watching either horror
movies or non-scary documentaries.
The women who wore the sweat-containing gauze did significantly
better on word-association tests than those who did not.
"It is well-documented in the research literature that
animals experiencing stress and fear produce chemical warning
signals that can lead to behavioral, endocrinological and
immunological changes in their fellow animals of the same
species, but we wanted to see if this applies to humans as
well," said lead researcher Denise Chen, assistant professor
of psychology at Rice University.
Those women exposed to fear chemicals were 85 percent accurate
when it came to processing meaningfully related word pairs,
while those exposed to nothing or neutral sweat were 80 percent
"We demonstrated that in humans, chemical signals from
fear facilitated overall accuracy in identifying word relatedness
independent of the perceived qualities of the smells,"
Chen said. "The effect may arise from a learned association,
including greater cautiousness and changes in cognitive strategies."
Synchronized Menstrual Cycles
If you are a woman, you may have already noticed that at
some point in your life your menstrual cycle seemed to magically
start and end at the same time as your close friends, family
or co-workers. This is something that women sharing the same
office, dorm, apartment, home or workspace often report.
Martha McClintock, PhD, who, in 1971 as an undergraduate,
first published a study showing that menstrual cycles among
women living together converged at the same time each month,
found that this phenomenon is not just a coincidence.
She conducted a study at the University of Chicago that found
women's menstrual cycles change in response to the scent of
perspiration from other women. When women were exposed to
the smell of other women's perspiration, it caused their menstrual
cycles to speed up or slow down.
The nature of the change depended on when the sweat was collected
-- before, during or after ovulation.
"We had provided the first evidence that pheromones
could affect physiology [the timing of ovulation]," said
McClintock of herself and colleagues. "Now, we wanted
to see if they could affect behavior. And yes, we found that
they are psychologically potent."
Although the study did not identify the chemicals that cause
this response, many cite this study as one of the first to
support evidence of human pheromones.
Mothers Know Their Babies Chemically (and Vice Versa)
At the heart of the entire issue of pheromones and chemical
signals is whether or not humans have a vomeronasal organ
(VMO), which is what animals use to detect the chemical signals
of other animals.
Although one has not been identified in humans, some researchers
think that pits in humans' nostrils may indicate a VMO, but
there's controversy over whether or not it works.
Further, a study by Duke University researchers found that
pheromones can activate the main olfactory system in mice.
In other words, humans may respond to pheromones through our
regular sense of smell, no VMO needed.
But while the method remains unclear, one thing is for certain.
There must be chemical communication among humans, says Charles
Wysocki, PhD, of Monell Chemical Senses Center.
"We know it's chemical, but is the information being
transferred pheromonal?" asks Wysocki. "No one knows."
An interesting display of these chemical signals involves
mothers and their babies. Studies have shown that infants
respond to breast pads worn by their mothers, but not those
worn by other women. And, women are able to pick a T-shirt
worn by their infant from a pile of T-shirts.
Many experts remain skeptical that perfumes and other
products enriched with so-called human pheromones can
make a person more attractive to the opposite sex
Pheromones Affect Us, But No One Knows How
Most experts do agree that humans emit pheromones, and that
these chemical signals play a role in human interactions.
However, while their impact may be significant (scientists
are still trying to determine how pheromones affect humans,
and to what extent), it is not the same impact experienced
"They don't work directly, but can modulate how we feel
and influence our moods," McClintock said. "A pheromone
won't make you suddenly turn on the sidewalk and follow somebody's
perfume trail, or stand there dumbstruck, unable to move --
as they do, in effect, in animals and insects. But they definitely
do have an effect on the emotional state of people."
Potential uses for pheromones are vast, but the jury is still
out on whether or not any of these will come to fruition.
Some researchers say pheromones could be used as a mood enhancer
to alleviate depression and stress and increase sexual desire.
Others have branched off of the studies about pheromones and
menstrual cycles to suggest they may be used as fertility
treatments or contraceptives.
It has even been hypothesized that pheromone treatment may
control prostate activity in men, thereby reducing the risk
Further, studies have found that chemical signals may in
fact play a role in who we select for a partner. It may not
be based entirely on factors we can assess, like personality,
sense of humor, looks, etc. Instead, it may be based on a
person's immune system genes.
Selecting a mate whose immune system genes are as different
from your own as possible ensures the best chance for fighting
off disease. Mice do this inherently using some type of odor
or odor/pheromone signal. It turns out humans may too.
Geneticist Carole Ober, PhD, and colleagues at the University
of Chicago have been studying an isolated group of people
in the United States and Canada called the Hutterites.
Although the group is highly removed from outside populations,
and therefore highly inbred, upon examining the genetic makeup
of 411 married couples, Ober found that fewer than expected
Hutterites chose a mate who was similar in immune system genes.
In fact, couples rarely shared a similar cluster of genes,
which would have been expected in an inbred society
What About Those Pheromone Perfumes?
Many products have hit the market claiming to contain pheromones
that will help you attract a member of the opposite sex. Do
Many experts remain wary, but reportedly 74 percent of those
who tested a pheromone product called Athena, developed by
Dr. Winifred Cutler, a biologist and behavioral endocrinologist,
had pleasant results. They experienced an increase in hugging,
kissing and more, so perhaps the only answer is to try one
and see for yourself -- or leave it up to your own pheromones
to do the job!
Top Six Signs that Someone is Physically Attracted to You
Four Most Common Hormone Disorders in Women
Daily April 1, 2006
Scientist: Big Clue to Human Pheromone Mystery
Sense Detects Pheromones, U. of C. Researchers Show
Potential Participants in Your Sex Life
Psychological Association: Communicating Through Pheromones