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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.

Chemical Signals

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 accurate.

"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.

Chemical Signals

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 by animals.

"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 of cancer.

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 they work?

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!

Recommended Reading

The Top Six Signs that Someone is Physically Attracted to You

The Four Most Common Hormone Disorders in Women


Science Daily April 1, 2006

New Scientist: Big Clue to Human Pheromone Mystery

Sixth Sense Detects Pheromones, U. of C. Researchers Show

Pheromones, in Context

Pheromones: Potential Participants in Your Sex Life

American Psychological Association: Communicating Through Pheromones

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