We are searching data for your request:
Upon completion, a link will appear to access the found materials.
Many animal species are capapble of secreting and also detecting pheremones from members of the same species, which relay messages and signals such as indicating sexual readiness.
Do humans do the same thing? Are humans capable of communicating in this subconscious fashion?
Yes, humans can secrete and sense pheromones, e.g. female tears dampen male sexual arousal.
Science 2011, 331(6014), 226-230
But then on the other hand, a key gene in mouse sex specific behavior (TRPC2) is a pseudogene, i.e. it is inactive, in humans.
Nature 2007, 448, 1009-1014
If you look at the references in those papers you will probably find a lot more examples.
- Previous studies found both men and women produce sex pheromones
- New research has found these pheromones trigger our subconscious
- During tests, men could correctly identify the smell of a women
- While gay men were equally able to distinguish the sex smell of men
Published: 17:56 BST, 1 May 2014 | Updated: 00:05 BST, 2 May 2014
Research found sex pheromones trigger our subconscious and men, in particular, are able to sniff out the gender they're attracted to. Stock image
If you remove deodorant, perfume and the smell of washed clothes, all of us give off a unique and distinctive scent - especially when we're on the lookout for a mate.
Previous studies have found genders produce sex pheromones, but new research has discovered these pheromones trigger something in our subconscious.
Researchers found we are able to sniff out the gender of the sex we're attracted to.
During tests, not only did men recognise the smell of women, but gay men were equally able to distinguish the sex smell of men, too.
Lead researcher Wen Zhou from the Chinese Academy of Sciences said: 'Our findings argue for the existence of human sex pheromones.
'They show that the nose can sniff out gender from body secretions even when we don’t think we smell anything on the conscious level.'
Whiffs of the active steroid ingredients androstadienone in males, and estratetraenol in females influence our perceptions of movement as being either more masculine or more feminine, the study found.
Earlier studies found androstadienone, present in male semen and armpits, can promote positive mood in females as opposed to males. Estratetraenol, first identified in female urine, has similar effects on males.
Pheromones in Humans: Myth or Reality?
Pheromones are volatile, odorous substances which are released by one animal and detected by another, causing some sort of physiological reaction. These reactions can manifest themselves in a variety of different ways: some pheromones modulate sexual activity, some affect aggression, some play roles in territory marking, and other pheromones have similarly diverse effects on the target animal. Pheromones have been demonstrated in a very large number of organisms ranging from amoebas to fish to mammals, including primates. However, the question of whether human olfactory signals exist has been a question of much debate and few definite conclusions. In this paper I will look at some possible examples of odor signaling in humans.
Mammals of all sorts use olfactory signals to indicate willingness to copulate, define territory, mark their young, and signal aggressive intent. These processes can be seen in many animals used as models for human systems, including rats, monkeys (both Old World and New World), hamsters and mice. The fact that pheromones are important biological signals in a plethora of other species indicates that the possibility of human pheromones should not be discarded lightly.
Although humans generally rate olfaction as their least important sensory modality, we still spend billions of dollars, years of our life, and a considerable amount of effort to modify the way we smell (at least in industrialized countries). These efforts typically include scrubbing with deodorant soaps and scented shampoos, applying deodorants to those parts of our bodies we feel need deodorizing, and finally applying perfumes and sprays to replace those natural odors we just discarded down the shower drain. This points out an obvious contradiction: if olfaction is considered unimportant and possibly even obsolete, why do we work so hard to change the way we smell? The first question to address is where do these odors we produce come from? Whereas animals release pheromones from their skin, urine, feces, and to some extent breath, most research on pheromones in humans indicates that the main odor-producing organ is the skin. For the purposes of this paper, the skin is what I will focus on. These odors are largely produced by the skin's apocrine sebaceous glands, which develop during puberty and are usually associated with sweat glands and tufts of hair. These glands are located everywhere on the body surface, but tend to concentrate in six areas1:
1) The axillae (underarms)
2) The nipples of both sexes2
3) The pubic, genital, and circumanal regions
4) The circumoral region and lips
5) The eyelids
6) The outer ear
The first four of these regions are generally associated with varying amounts of hair growth, which makes perfect sense, as the extremely large surface area of a tuft of hair is a very effective means of spreading an odor by evaporation. The fact that body hair and apocrine glands appear simultaneously at puberty is significant and suggests that body odor and its dispersal may be linked to sexual development. These supposedly non-functional structures, coupled with the olfactory system, would be called part of a pheromonal system in any other mammal.
The substances produced by these glands are relatively imperceptible by the human nose what we smell when we detect skin odor is not the fresh glandular secretions but rather the bacterial breakdown products of these glandular secretions. The sebaceous secretions themselves consist mostly of lipids such as squalene and other esters. When degraded by enzymes of bacteria naturally present on human skin, free fatty acids result, including those that smell hircine and are generally regarded as unpleasant. The most prominent examples of these hircine fatty acids have the general formula (CH3(CH2)nCOOH) and are called butyric acid (n=2), caproic acid (n=4), and caprylic acid (n=6).
The first studies I will discuss relate to evidence for the existence of pheromone signaling in human babies and children. The first interesting studies regarding children come from Michael Kalogerakis and Irving Bieber. They proposed a theory that olfaction is related to sexual identification in young children. Kalogerakis performed a study on young boys, two to four years of age, which strongly indicated that at some point in early childhood, a boy will begin to show an aversion to the odors of their father, and will simultaneously feel attraction to the odors of their mother. According to Bieber, this indicates a shift in sexual interest and acts as a biological trigger for the Oedipus response. Kalogerakis supports this theory with a case study of a boy named Jackie, who originally was closer to his father, but at the age of three years, three months, began to show a distinct preference for his mother's smells, especially at times right after she and Jackie's father had been having intercourse. At four years of age, Jackie would become nauseous at the smell of his father. This behaviour continued, tapering off slowly until Jackie was six, and his sexual identity had presumably been established.
Another intriguing study was carried out by Michael J. Russell of UCSF in 1976. He enlisted the help of ten recent mothers, whom he asked to wear a cotton pad in their bra for three hours before testing. Russell then tested the sleeping babies' ability to differentiate between pads worn by their own mothers and those worn by strange mothers. At the age of two days, only one of the ten babies responded to either type of pad, and he responded to both with a sucking response. At the age of two weeks, eight babies responded by sucking to a stranger's pad, and seven responded to their mother's pad. Also, one child responded only to its mother's pad. At the age of six weeks, however, things had changed. Eight babies responded to their mother's pad, one responded to a stranger's pad, and one did not react to it's mother's pad but did react with a jerk and a cry to the stranger's pad. These results may indicate either that a baby imprints on its mother's odor, or as Russell suggests, that the mother unconsciously marks her baby with a distinctive scent, a phenomenon observed in many other primates. This latter possibility is supported by the common parental observation that a child will reject their favorite blanket or stuffed animal after it has been washed, presumably because it has lost specific odors acquired in previous contacts.
A final childhood phenomenon worth mentioning is one observed by Dr. Alex Comfort. Comfort noticed that in the past three centuries, the age of onset of menstruation for girls has had a direct correlation with the amount of time that young girls spend with boys. In pre-Victorian times, menstruation began at an early age, only slightly above the average age of onset now. However, in Victorian times, when mingling between the sexes was minimized as much as possible, the average age of onset climbed a few years. In post-Victorian times, as boys and girls were allowed to mingle more freely and coeducation appeared, the average age fell once again. Admittedly, this could be due to a number of other factors, but it is Comfort's opinion that it is due to the exposure to odors of the opposite sex. In fact, this phenomenon has been documented in mice and is called the Vandenbergh effect: female mice raised alone in sterile cages have a much higher age of maturation than that of female mice raised alone in cages filled with a male mouse's bedding material. When the bedding belonged to a castrated male mouse, this effect was not observed.
There are variations in odor perception between human adult males and females. Le Magnen and Doty found that this is most evident in the case of women's acute ability to smell musk3, which are steroids, large cycloketone or lactones, often with side chains which are most likely involved with their biological specificity of action. All of these compounds are very similar to the male sex hormone testosterone (see appendix for structures). Whereas women are very sensitive (1 part in 109) to the musky odors of civetone (from the anal glands of the civet cat and used in many perfumes), exaltolide (a synthetic musk), and boar taint substance (a sexual attractant produced in the preputial glands of the boar), men are relatively insensitive (1 part in 106) to these substances. Moreover, women's sensitivity to these substances varies as a function of where they are in their menstrual cycle: during menstruation, women are no more sensitive to musks than men, but about ten days after menstruation (ovulation -- a woman's peak fertility period), women reach their maximum sensitivity. In addition, women on the pill, women who have had ovarectomies, pregnant women, and post-menopausal women are relatively insensitive to these substances. Le Magnen deduced from these results that sensitivity to musk in women is critically defendant on the levels of estrogen in the blood: during ovulation, serum estrogen is at a peak, whereas serum levels of estrogen are low during menstruation, pregnancy, in post-menopausal women, women who have had ovarectomies, and birth-control pill users. Further, it is the action of progesterone which causes nasal congestion during menstruation and pregnancy4, and might be responsible for the reduced sensitivity at these times.
Why is this relevant? Men secrete musky odorants in abundance. The -3-ol precursor of boar taint substance is found in male urine, and substances similar to testosterone, such as androstenone, are secreted in the smegma and from the apocrine glands of the underarms5 and pubic area of males. As is usually the case, bacterial action may be necessary for the release of the odorants. The fact that men's bodies secrete these substances and that women are maximally sensitive to them when they are most fertile indicates that there may be a olfactory-sexual role for these substances in human sexuality.
Indeed, a study performed by J. Richard Udry at the University of North Carolina attempted to delineate the relationship between coitus, orgasm and position in the menstrual cycle. He found that women do indeed engage in sexual intercourse about six times more frequently at about the time of ovulation, when women's sensitivity to the male musk odor is highest. In addition, the women are much more likely to have an orgasm at these times. Further, the women Udry studied women were several times less likely to have sexual intercourse or have an orgasm during and two to three days after menstruation, which is when women's sensitivity to the musky smell of men is lowest. Coupled with women's odor sensitivity, these results could indicate a possible pheromonal trigger for sexual behaviour.
There are several other effects in adult humans which might hinge on pheromones. Some of the most interesting results come from work done by Martha McClintock at Harvard. She performed a study on menstrual cycles in women who lived together in dormitories and found that when women are housed together, their menstrual cycles tend to synchronize and lengthen. She also found that the lengthening effect was attenuated in direct relation to the amount of time these women spent with men. In one woman's case, her regular cycle was six months long, but when she started seeing a man, it dropped to four and a half weeks. After she stopped seeing this man, her cycle once again lengthened. Of course, in an experiment like this, it is difficult to eliminate diet, work and sleep habits as factors, but the fact that this is such a widespread phenomenon indicates that something more basic is probably at work here. It is to be stressed that airborne odors or pheromones were not directly demonstrated in this study, but there is an identical phenomenon in mice that has been shown to be pheromonal in nature. This effect is called the Lee-Boot phenomenon, in which groups of female mice housed together experience increases and synchrony in their estrus cycles. When a female mouse is housed alone, this effect does not occur, but when a solitary female mouse is kept in a cage supplied with bedding from a cage full of female mice, the Lee-Boot effect is once again observed, indicating that the cues are chemosensory in nature. The attenuation of cycle elongation in women in response to male contact is also echoed in mice, and is called the Whitten effect. Once again this effect has been shown to be due to olfactory signals.
Michael Russell provided some more insight on the phenomenon of menstrual synchrony. A colleague of his, on reading McClintock's paper, mentioned that she too had noticed the same phenomenon among her friends, except that in every case, it was her own menstrual cycle which determined the synchronization of her friends'. Upon hearing this, Russell asked his colleague if he could use her underarm scent to help confirm and extend McClintock's findings. She consented, and proceeded to wear sterile cotton pads under her arms regularly. Russell the recruited sixteen female volunteers, each of whom came in three times a week for four months to have a liquid applied to her upper lip. One group of women had pure alcohol applied to their lips, and the other group had a mixture of alcohol and Russell's colleague's underarm scent from the previous day applied. The group which received pure alcohol did not experience changes in their menstrual cycle, but those that had the mix of alcohol and underarm scent applied showed a radical change in their cycles: The average time lag between cycles had been 9.3 days, but after four months, this had decreased to 3.4 days, and fully half the women were in exact synchrony with Russell's colleague, discounting the the aforementioned one day time lag. None of these women had ever even met Russell's colleague. McClintock's study showed that women who lived together reported menstrual synchronization, and Russell's study provided a likely mechanism: underarm scent. Another possible interpretation of this study leads to the conclusion that there may be dominant women with regard to menstrual synchrony, a phenomenon observed in many animals.
Dr. Russell provided yet another interesting result. At the same time he was performing his experiments on babies' ability to discriminate between their own mothers and strange mothers, he performed another experiment on whether young adults could discriminate between their odors and others' and between male and female odors. Twenty-nine college age students, 16 male and 13 female, were asked to wear a clean undershirt for twenty-four hours without using soap, deodorants, or perfumes. After twenty-four hours passed, the shirts were collected and put in buckets with the armpit right above a strategically placed sniffing hole. Two tests were then performed: the subjects were presented with three shirts, one theirs, one from a strange female and one from a strange male. The subjects were then asked to identify which shirt was theirs, taking as much time as needed. The subjects were then asked to identify which shirt belonged to the strange male and which shirt belonged to the strange female. The subjects generally sniffed each bucket once in succession, and then repeated the process. The results were impressive: 81% of the males and 69% of the females identified their own shirts correctly, for an average success rate of 75%, which is highly significant when compared to the chance percentage of 33%. In the second sex-identifying test, the subjects performed just as well: 81% of the males and 69% of the females were correct, for an average of 75%. Once again, this result was very significant, as chance would dictate a 50% success rate. When asked to characterize the odors of the shirts, the subjects generally said the males' shirts smelled musky and the females' shirts smelled sweet. This observation jibes well with the previous discussion of variations in odor perception.
One final effect needs to be mentioned due to large amount of research on it. There have been many studies on whether or not human vaginal secretions might contain some kind of sex pheromone (or "copulin", as one researcher calls them). Several researchers have found that human vaginal secretions contain various small (C2 to C6) fatty acids, with acetic acid predominating. Richard P. Michael found that about 30% of the women (he called them 'producers') produced a significant amount of those small fatty acids (not including acetic acid) that induce copulatory behaviour in infra-human monkeys. In addition, these "copulins" increased up until ovulation, and then decreased as menstruation approached. Michael also noted that women on birth-control pills did not show this mid-cycle increase, and had a lower overall fatty acid content. Michael theorized that these fatty acids or "copulins" were a sexual trigger in humans, but this has never been demonstrated, although the producers' secretions did increase copulatory behaviour in rhesus monkeys. When David Goldfoot's group in Wisconsin tried to confirm these results, however, they were unsuccessful.
Are pheromones in humans a myth or are they real? At this point, it is difficult to say either a definite yes or a definite no. The field is obviously very confused, and for every paper one finds that seems to demonstrate the existence of human pheromones, one can find another equally compelling study refuting their existence. In this paper I have tried to consider a few compelling bits of evidence, but it should be noted that none of these results are yet widely accepted, and no pheromone has yet been isolated and conclusively linked to a physiological effect in humans. Further, much of the work in this field is of a qualitative nature, without adequate controls or firm statistical basis.
However, some of the results mentioned above are quite compelling. McClintock's study and Russell's extension seem to strongly indicate there is some odorant that affects women's menstrual cycles. The fact that men secrete musk-like substances that women are maximally sensitive to during ovulation coupled with the finding that there is a demonstrated increase in coitus during this period is also very intriguing. "Copulins" may or may not be human sexual releasers, and they seem to stimulate copulatory behavior in monkeys, although this result has not been confirmed.
To close, I would like to propose a new way of looking at pheromones, specifically in humans. With our highly developed intellect and rich compliment of emotions, ambitions, motivations and desires, it may not be profitable to look at human pheromones the same way we look at animal pheromones. Instead of looking for odorants that cause a definite physiological response, it may behoove us to look at how possible pheromones affect our attitudes. We are not machines that blindly fall into some stereotyped behaviour in response to an odor, but we may be machines that are nudged towards a type of behaviour by pheromones in concert with our higher intellect.
1. This is an overgeneralization there are substantial differences in apocrine gland distribution and quantity between the various races. The six areas outlined here are generally found in caucasians, but blacks and Aborigines tend to have more and larger glands, with a higher number on the chest and abdomen than is found in an average caucasian. In addition, Aborigines have a much more powerful scent gland in the circumanal region. Asians, on the other hand, tend to have smaller and far fewer apocrine glands than either Caucasians or blacks, and many have none at all. In fact, only about 10% of Japanese people have any underarm odor at all, and at one point having scent glands in the underarms qualified a Japanese male for a military exemption and a free ticket to a medical center where they could receive treatment.
2. Interestingly, the mammary glands themselves are highly modified apocrine glands
3. Musk is a basic ingredient of all perfumes and colognes.
4 . This phenomenon might be responsible for womens' reputed proclivity for unusual foods during pregnancy and menstruation.
5. A note about underarms: many of the authors of the references for this paper have pointed out that underarms are the ideal location for the dispersion of odors and /or pheromones. This is because 1) They are among the warmest parts of the body, and are among the first parts to perspire. 2) They are amply endowed with apocrine and sweat glands. 3) There is usually a strong growth of hair, which is a very effective means of dispersing an odor (as noted above). 4) Underarms are high on the torso and thus well-situated to disperse odors in the region of other people's noses. 5) Finally, being under the arms, armpits are protected from excessive evaporation. To release odors, the arms must be raised or in motion. Comfort speculates that underarms may even be specialized for this purpose.
1. Hopson, Janet. Scent signals: The Silent Language of Sex. New York: William Morrow and Company, 1979
2. Stoddart, D. Michael. Mammalian Odours and Pheromones. London: Edward Arnold Ltd., 1976
3. Shorey, H.H. Animal Communication by Pheromones. New York: Academic Press, 1976
4. Vandenbergh, John G. (ed). Pheromones and Reproduction in Animals. New York: Academic Press, 1983
5. Doty, Richard L. (Ed). Mammalian Olfaction, Reproductive Processes, and Behavior. New York: Academic Press, 1976
6. Theimer, Ernst T. (Ed). Fragrance Chemistry: The Science of the Sense of Smell. New York: Academic Press, 1982
7. Wells, F. V. and Marcel Billot. Perfumery Technology Art: Science: Industry. Chichester: Ellis Horwood Ltd, 1981
8. Comfort, Alex. "Likelihood of Human Pheromones." Nature, vol. 220, pp. 432-479
9. McClintock, Martha K. "Menstrual Synchrony and Suppression." Nature, vol. 229, pp. 244-245
10. Russell, Michael J. "Human Olfactory Communication." Nature, vol 260, pp.520-522
11. Udry, J. Richard and Naomi M. Morris. "Distribution of Coitus in the Menstrual Cycle." Nature, vol. 220, pp. 593-596
12. Michael, Richard P. et al. "Volatile Fatty Acids, 'Copulins', in Human Vaginal Secretions." Psychoneuroendocrinology, vol. 1, pp. 153-163
13. Huggins, George P and George Preti. "Volatile Constituents of Human Vaginal Secretions." American Journal of Obstetrics and Gynecology, vol. 126, pp. 129-136
14. Kalogerakis, Michael G. "The Role of Olfaction in Sexual Development." Psychosomatic Medicine, vol. 25, pp. 420-432
15. Bieber, Irving. "Olfaction in Sexual Development and Adult Sexual Organization." American Journal of Psychotherapy, vol. 13, pp. 851-859
16. Michael, Richard P. et al. "Human Vaginal Secretions: Volatile Fatty Acid Content." Science, vol. 186, pp. 1217-1219.
© 1994-2014 Melissa Kaplan or as otherwise noted by other authors of articles on this site
Do Human Pheromones Exist?
Jan 23, 2018
ISTOCK, JACOB WACKERHAUSEN
S earch for &ldquopheromones products&rdquo on the internet, and dozens of sprays and perfume additives will appear&mdashmany claiming to be able to increase your attractiveness to the opposite sex. Some companies, such as the Athena Institute, which, according to its founder, Winnifred Cutler, published its 108th consecutive ad in The Atlantic this month, assert that scientific studies back up their claims.
While there have been several experiments examining the effects of compounds extracted from people&rsquos armpits, much of the data on sex-related behaviors, The Scientist has found, go back more than a decade and were met then&mdashand still now&mdashwith skepticism from pheromone researchers. &ldquoI am not compelled by any studies that are out there that say there is an active steroid component from the underarm that causes [sexual attraction],&rdquo says George Preti, an organic chemist at the Monell Chemical Senses Center in Philadelphia who conducted.
The problem with [pheromone] companies is not specific to them. It’s a much more general question about claims made without good evidence.—Tristram Wyatt, Oxford University
Within the scientific community, pheromones are broadly defined as chemical signals released by an animal that induce specific effects on other members of the same species. Although these substances are typically associated with sexual attraction, researchers have found they can have a broader range of influence, such as prompting aggression or modifying parental behaviors.
While pheromones are well-defined among other members of the animal kingdom, the presence of such molecules in humans remains controversial. “I still have an open mind about whether human pheromones exist,” says Ron Yu, an investigator at the Stowers Institute for Medical Research who studies rodent pheromones. “But I just don’t find any of the published studies convincing enough.”
Cutler disagrees. There is robust scientific evidence, she argues, for the Athena Institute’s pheromone cosmetic fragrance additives, which are sold to both men and women and cost approximately $90 per two- to four-ounce vial. “We at Athena, as well as independent researchers, have tested the efficacy of Athena’s pheromones as sexual attractants using double-blind, placebo-controlled protocols,” she tells The Scientist.
The human pheromone experiments
In 1986, Cutler and her colleagues published a pair of studies in Hormones and Behavior that reported that both male and female armpit secretions could shift women’s menstrual cycles. These findings were widely covered by the press—The Washington Post, for example, ran a story titled, “Pheromones Discovered in Humans,” which stated that the team was the first to establish the existence of pheromones in people. The reporter did note, however, that “[t]he human pheromones are not sex attractants, nor do they act almost immediately as animal pheromones do. Instead, the human pheromones act over a period of weeks or months to alter the timing of women’s menstrual cycles.”
Around the same time, Cutler established the Athena Institute and, a few years later, she created two trademarked pheromone products, Athena Pheromone 10:13 for women and Athena Pheromone 10X for men. These formulations, which Cutler says are synthesized copies of chemical substances isolated from armpit extracts, were tested in three published, double-blind, placebo-controlled investigations: the effect of the latter was tested in 38 men by Cutler and her colleagues, and the former was examined in studies by two teams of independent researchers. One study included 36 female university students and the other 44 postmenopausal women. All three papers reported that individuals who received the pheromone formulation reported increased frequencies of sexual behaviors, including kissing, formal dates, and sexual intercourse.
Despite what appeared to be promising results, Preti was skeptical. “I’m not excited by this paper and I’m wary of this mystery chemical,” he told New Scientist in a 2002 story about the study on female university students. Preti, who coauthored both 1986 papers about the effects of armpit extracts on menstrual cycles with Cutler, still expresses that doubt today. Without knowing what the compounds are, he tells The Scientist, scientists cannot repeat these experiments to validate their effects.
When asked about her pheromone formulas, Cutler says that her products were carefully selected from human underarm extracts, “based on my analysis of a world of literature that I do not let my competitors know about.”
Other issues associated with these studies, according to Yu, are the relatively small sample sizes and their reliance on self-reported behaviors. As a result, he says, “I don't think [these studies] are powerful enough to draw a solid solution.”
The hunt for human pheromones
In the literature, there are four compounds that are commonly cited as potential human sexual attractant pheromones, androstenone, androstenol, androstadienone, and estratetraenol.
Despite their prevalence in scientific studies and consumer products, Tristram Wyatt, a zoologist at the University of Oxford, argued in a 2015 Proceedings of the Royal Society B paper that there was no scientific basis for claiming these molecules were pheromones at all. Androstenone and androstenol, he says, were proposed simply as a matter of coincidence, when researchers discovered molecules in the human armpit that were known to act as pheromones among pigs. Subsequent studies were not able to provide sufficient proof that these compounds influence human behavior.
I still have an open mind about whether human pheromones exist. But I just don’t find any of the published studies convincing enough.—Ron Yu, Stowers Institute for Medical Research
Androstadienone and estratetraenol have an unusual origin story. They were first proposed by the pheromone company EROX in the early 1990s. “No evidence of how they found these molecules and chose them out of all the potential hundreds was ever published,” Wyatt tells The Scientist. Still, many studies have utilized these molecules. As recently as 2014, a group of researchers published a study in Current Biology, reporting that these molecules could convey masculinity or femininity to members of the opposite sex. Last year, another team contradicted these results in a study published in Royal Society Open Science.
“The problem with [pheromone] companies is not specific to them,” Wyatt says. “It’s a much more general question about claims made without good evidence.”
There is, however, more convincing evidence of human pheromones that are not involved in sexual attraction, according to Preti—for example, compounds that modulate menstrual cycles or hormone release.
Scientists have also observed that a secretion from areolar glands on a lactating mother’s nipples will induce a suckling response in an infant, even if the child is not her own. “If it should turn out that the preliminary observations of the pheromone in babies is correct, and the molecules could be identified, that would give greater confidence for researchers to start serious study of possible human pheromones in a sexual context,” Wyatt tells The Scientist. “But it’s perfectly possible that pheromones are not involved in human sexual behavior—we are complex animals, and other cues and signals may have evolved to take their place.”
As for pheromone products, the main active ingredient in them is likely “hope,” Wyatt says. “The placebo effect is strong. If you have spent $50 on something to add to your perfume, you might go out to the bar with greater confidence, and that’s how an effect by individual consumers could be realized—but it’s not because of anything in the products.”
First Evidence of a Human Response to Pheromones
Scientists have found evidence of a response to pheromones in the human brain, a new report says. These volatile compounds--secreted by one member of a species to elicit a response (either behavioral or physiological) from another individual--and their use in communication has long been documented in lower mammals such as rodents and pigs. But now, in a study published in the August 30 issue of the journal Neuron, scientists at Huddinge University Hospital in Sweden have detected a pheromone effect in humans.
Ivanka Savic and colleagues used positron emission tomography (PET) to scan the brains of 12 men and 12 women while the subjects smelled synthetic versions of compounds related to the hormones estrogen and testosterone. The estrogen compound caused the men to experience increased blood flow to the hypothalamus, the region of the brain rodents use for pheromone detection, but had no effect on the women. The testosterone-related compound, meanwhile, caused heightened blood flow in the women, but not the men.
Such gender-specific reactions in the brain lend strong support to the theory that humans can detect pheromonal signals, although the exact pathway for detection is as yet unknown. Indeed, the researchers concede that the existence of human pheromones remains an open question but believe their current study calls for "further, extensive research of chemosensory signals in humans."
Can Pheromones Really Make You More Attractive?
The short answer is yes. For decades, scientists have debated the effectiveness of human pheromones, but there’s a growing amount of evidence to suggest that they do indeed play a role in the way we perceive others.
Experiments have proven time and time again that sex pheromones trigger an arousal response in the brain. While the jury is still out on exactly how we sense and perceive these chemical signals, there’s no doubt that we are in fact affected by them.
Of course, pheromones are limited in what they can do – after all, there’s no such thing as a magic love potion. Wearing a scented cologne might make you more attractive to women, but it won’t change who you are, your actions, fix damaged relationships, or make every woman in the room want to sleep with you. You still have to make the effort to socialize and act on a woman’s feelings of attraction. Think of pheromones as something that can enhance the good qualities you already have, not a way to make yourself something that you’re not.
Humans Emit Sex Scent Signals
Aug. 29, 2001 -- While it is well documented that females and males of many species can communicate through chemical signals called pheromones, there has remained some question as to whether humans can communicate this way as well.
Using brain imaging, Swedish researchers have found new evidence that men and women can in fact send and receive subconscious odor signals. And, that men and women, it seems, respond to the smells differently.
Pheromones are airborne chemical messengers released from the body (through, for example, sweat and urine) that have a physical or emotional effect on another member of the same species.
Most animals smell or "sense" pheromones through a specialized half-moon shaped structure located inside the nose called the vomeronasal organ. Pheromone signals picked up by the organ are then relayed through nerves to an area of the brain called the hypothalamus, which is well known for its ability to alter emotions, hormones, reproduction and sexual behavior.
Ordinary, non-pheromone smells such as the scents of food or flowers are recognized by a different part of the nose called the olfactory epithelium.
Evidence of Human Pheromones
The strongest evidence for pheromone signaling between humans had been revealed by Dr. Martha McKlintock, who discovered in 1998 that the menstrual cycles of women living together tend to synchronize because of the chemical messages released in their sweat.
The latest study, which appears in this week's issue of the journal Neuron, used PET (positron emission tomography) scanning techniques to analyze the brains of 24 men and women while they smelled chemicals almost identical to the naturally produced sex hormones estrogen and testosterone.
Dr. David Berliner, an expert in the field of chemical signaling and CEO of Pherin Pharmaceuticals, which produces synthetic pheromones, says: "These findings corroborate that human pheromones do exist, and that women can communicate chemically with men and vice versa. This is a very important finding because it shows specific areas of the brain that are activated by these chemicals."
The scientists, led by Dr. Ivanka Savic of the Karolinska Institute, found that the hormone-like smells "turn on" the brain's hypothalamus, which is normally not activated by regular odors.
They also found the brains of men and women respond very differently to the hormones.
Women's hypothalami are activated when they smell the chemical similar to testosterone but not to the estrogen-like substance, whereas men's hypothalami have the opposite response: They are turned on only by the estrogen-like chemical and not the testosterone-like one. There is also sexual disparity between the specific sub-regions of hypothalamus that are activated.
In other words, the way we chemically perceive the opposite sex is very different than the way we perceive members of the same sex. Researchers believe this could explain why some of our behaviors are gender-specific.
Can Pheromones Make Us More Sexually Attractive?
If these pheromones turn on areas of the brain that control mood, hormones and sexual behavior, one might then ask: "Can these chemicals make us more attractive?"
The answer is: Maybe. Researchers at the University of Chicago and University of Utah have found that the same sex hormone-like chemicals used in the Swedish study can in fact have a pheromone effect by producing changes in mood, heart rate, breathing, and body temperature. However, there is currently no indication these chemicals can actually increase sexual arousal or attraction.
Many perfume companies have tried to capitalize on the potential sex-specific effects of these chemicals by adding them to their fragrances. But most of these companies add hormones from animals such as pigs and deer, so they probably don't work. Pheromones are generally species-specific, so a perfume enhanced with pig pheromones is really only useful for other pigs.
The promotions of one company that adds human hormones to its fragrances claim the additives will "put you and your partner at ease, boost your confidence, and contribute to a feeling of well being." The general idea is that pheromone perfume can replace our naturally produced pheromones that have been washed off through bathing and hidden by layers of clothing.
If these claims are true, pheromones may make us more attractive to potential mates by bringing out our best qualities and allowing us to appear more self-assured and relaxed. That "feeling of well being" may also make us a lot more pleasant to be around.
Pheromones as Therapeutics
The ability of these sex hormone-like chemicals to activate areas of the brain that control hormones indicates they may have more broad-ranging therapeutic value as well.
For example, Pherin Pharmaceuticals is currently developing numerous synthetic pheromones that it hopes will be effective in decreasing symptoms of anxiety disorders, premenstrual syndrome in women, and prostate enlargement in men.
Berliner has personally tested many of these compounds. "I love it!" he enthuses. "And it takes only seconds to work. It is very hard to explain with words, but it makes you feel relaxed. All of a sudden your internal life changes for the better, although the outside world has not changed at all."
Do humans secrete and detect pheremones? - Biology
If you haven’t already, please take the time to read the Introduction to Pheromones page.
A lot is written about pheromones on the internet, but much of the information out there is inaccurate. You can usually rely on “scientific” websites, but even they have their bad apples, some of which are displaying outdated information on pheromones or have fallen victim to the many pheromone fallacies that exist. Even worse are the plethora of junk pheromone stores which are the usual perpetrators and proliferators of the inaccuratepheromone information. Here we will be discussing exactly what a pheromone is (please note: not all of this is established science, but it is the most up to date understanding of pheromones even if it isn’t academically supported).
Definition of “PHEROMONE”
An amalgamation of the definitions of pheromones offered by www.dictionary.com is:
“A chemical secreted by an animal, usually associated with insects, which influences the behavior, physiology or development of others of the same species, often functioning as an attractant of the opposite sex.”
The word “pheromone” is derived from the Greek “pherein”, which means to carry, and hormon, which means to excite. Thus, pheromones can be described as an inter-body hormone, or a chemical that transmits a message between bodies. These messages are detected by other individuals which may or may not be of the same species, and usually signal something (be it fear, aggression, sexual arousal or many others) to those individuals. The effects of the detection of this signal carried by the pheromone or pheromones are varied and could range from sexual excitement to avoiding contact with an individual who is sending the signal. A more specific example of this is the reported altering of the phase of the menstrual cycle of women who live in close proximity, which has been linked to certain pheromones.
In mammals there are three groups of pheromones:
- Releaser pheromones that “release”, or cause, an almost immediate change in behavior. Examples of this include attraction and aggression.
- Primer pheromones have affects that are more long term, for example the altering of the phase of menstrual cycle in women.
- Information pheromones carry information about an individual. This might include fitness, immune system type (Major Histocompatibility Complex genes), etc.
Generally, the pheromones in pheromone products are hormone related. For example, androstenone, androstenol and androsterone are all androstenes, and generally signify factors involved with sex. Copulins, a group of pheromones only produced by women, are mostly acids and organic acids.
It is also interesting to note that pheromones are not necessarily species specific. For example, out of androstenone, androstenol and androsterone, only androsterone is uniquely human pheromone.
How pheromones are produced
In humans pheromones are secreted onto our skin through the apocrine glands (sometimes called human scent glands). These are similar to eccrine glands where our salty sweat comes from, but the apocrine glands secrete a more oily substance. The apocrine glands are normally associated with hairy areas such as arm pits and the crotch area, and are also usually accompanied by eccrine glands which help to disperse the pheromone secretions. Apocrine glands are activated at puberty, along with hair growth in the axillary (arm pit) regions and crotch which increase the surface area for pheromone dispersal. Certain pheromones are directly related to masculinizing or feminizing hormones (testosterone or estrogens), and so high levels of these hormones will cause high levels of the related pheromones to be released.
Pheromones evolved because metabolic waste (hormones, short peptide chains, fats, sugars, etc.) that was secreted onto an animal’s skin can give certain information about the internal chemistry and health of that individual. Over time species adapted to this fact giving rise to the whole pheromone chemical communication system. Modern animal and insect species have a somewhat more specialized pheromone system, where secretory glands and receptor systems have evolved.
Bacterial action may also have some role to play in pheromone production, but not much is known about this at the time of writing. For example, the pheromone androstenol may oxidise (by bacterial action) to androstenone. Androstadienone can also be converted into androstenone. However, bacteria are responsible for causing the bad smells associated with body odor, and they do this by metabolising the chemicals (including the pheromones) in the oily apocrine secretions. A study on bacterial action on pheromones can be found here.
Copulins are created in a different way to the “hormonal” pheromones. They are secreted into the vagina along with the bodies natural lubricant in redinness for sex.
How pheromones are sensed and processed
Pheromones fall under a category of chemical sensing (chemosensing for short) that is very similar to the way we smell. Our regular sense of smell (which is what you are using when you are smelling flowers) is called olfaction, but pheromones are thought to be detected and processed through an accessory olfactory system. In mammals this is the Vomeronasal System. This consists of vomeronasal pits situated somewhere in the nose, at the bottom of which lies the Vomeronasal Organ (VNO), which is where cells specialized for detecting pheromones lie. From here signals are sent by neurons (nerves) to the accessory olfactory bulbs, which is the part of the brain responsible for processing the information relayed by the pheromones and mediating a response. Most pheromone signals will end up at the hypothalamus. Interestingly, the epithelium of sensory cells in the nose is sometimes referred to as an extension of the brain because of their location and the way the signals are processed.
In humans, this picture of pheromone sensing becomes more complicated with some scientific studies casting some doubt over the existence of a VNO in humans, which it was thought would rule out the possibility of human pheromones having any effect on other individuals. There was also some doubt over the existence of the appropriate genes that would code for the pheromone receptor proteins in the receptor cells, making it even more likely that the pheromones being secreted onto our skin would be redundant. With this and the thoughts that our VNOs are vestigial, we are left with a situation where the whole pheromone system as an evolutionary relic akin to the appendix. Some suggest that this is due to the evolution of tri-colour vision, which led to an evolutionary trade off. However (and there had to be a “however”, or I wouldn’t be writing this!), anecdotal evidence from pheromone users has always contradicted the science in this regard, but only relatively recently has the science started to catch up with the anecdotal evidence.
First of all, (aside for anything concrete about the vestigality of the VNO in humans) there is no evidence that the VNO is actually required for pheromones to be detected, and current knowledge and speculation is leaning towards the idea that VNO is not the crucial pheromone sensing organ it was once thought to be, at least to the point of having the pheromone detection load shared with the generic olfactory membranes (click here for relevant study). There has also been significant evidence for the detection of pheromones having an impact on brain activity of specific areas of the brain (click here for relevant study), which has actually shown that the presence of that particular pheromone affects activity in parts of the brain linked with social cognition and attention. Incidently, while our organs of chemosensing in general have reduced in size, the areas of the brain associated with the processing of these signals have actualy grown in size compared to other areas. There is also evidence (click here for relevant study) that pheromones affect the release of Luteinizing Hormone which itself is responsible for causing temporary spikes in the release of sex hormones (specifically testosterone), which can happen during attraction and arousal.
Interestingly, the most abundant pheromone on the market is androstenone, but this pheromone has been shown to have no action in the VNO. The only male pheromone on the market that has shown to have an effect on the VNO is androstadienone, which is a less well known male pheromone. We are therefore left with two categories of pheromone, compounds that activate the VNO and those that don’t. The first type can be subcategorised into a group called vomeropherins, but normally all of the compounds are just labeled “pheromones”.
Contrary to popular belief, pheromones do have a perceivable odor that we can detect through normal olfactory pathways. This smell is mostly identified as an acrid bad body odor smell, but some pheromones have a more pleasant smell and some have been described as the scent of fresh sweat, in a good way. However, these smells are only detectable at high concentrations. The “pheromones are completely odorless” myth arose due to the fact that some of the action of pheromones which causes reactions in other people is subconscious, and the pheromones can be present in levels far lower than their detection thresholds for generic olfaction to have an affect. This means that pheromones do not have to be smelt to work. There are also those who can not actually smell androstenone (about 25% of the male population), although studies suggest that people’s noses can learn to smell androstenone (relevent study).
The affects of pheromones on behavior gets even more complicated in humans because we have evolved higher processing (consciousness) which can override, contradict or otherwise alter the affects our basic instincts have on our behavior. Take, for example, a situation where a guy is in a deeply committed relationship and is exposed to a very attractive signature of female pheromones. Here, higher processing would at the very least (assuming a high level of integrity on the guy’s behalf) cause the attraction to be ignored, and at the most could cause the guy not to notice the woman at all. Behavioral reactions to pheromones have another added layer of complexity due to the nature of attraction and courtship in humans, with factors such as social status (think about levels of “attainability” here) and shyness playing their part to inhibit pheromone influences, but there are other factors such as a persons tendency to be sexually aggressive or just aggressive in general that can amplify the normal pheromone effects. A persons mood prior to sensing the pheromones can also play a role. All of these factors are intensified with the use of exogenous (i.e. from a bottle) pheromones.
General pheromone discussion
The whole concept of using exogenous pheromones relies on there existing a kind of “human musk”, similar to the musk in deer. This musk would consist of many different pheromone compounds, each or by association with other pheromones carrying a message. Some of these messages are used as criteria in attraction an example of this would be testosterone levels in men. Several compounds may contribute to this message being transmitted, and some will signal “high testosterone” if they are secreted in high levels on the skin. These compounds or compound could then be identified and synthesized. However, the pheromones that are sold as pheromone products are only gross attraction pheromones, meaning that they only signal “high testosterone” or “youth” or “approachability” to everyone, and don’t give any information about the person behind these particular criteria. There is further evidence which suggests the existence of a very specific pheromone profile, but it will be made up of other compounds, probably relating to the immune system (opposite MHC genes, the “sweaty t-shirt study”, and this article) and other genetic qualities. It would therefore be possible to tailor a pheromone mix specifically for an individual, in essence creating the impression of an ideal partner, but at the moment this is beyond current technology.
The pheromone compounds that are commonly used in pheromone products are:
There are others, but these are the most common three. Click here for details on some of the general affects of these pheromones.
So, pheromones are not miracle sex attractants, but they do play a role in the day to day interactions of humans, albeit a more subtle one. They are a part of everyone’s life they say that only 10% of communication is verbal, but how much is pheromonal? More than you think maybe.
The scent of a woman — or a man
These patterns may look like random collections of dots, but to a person who's been sniffing certain chemical signals, they may look more masculine or feminine.
W. ZHOU ET AL/CURRENT BIOLOGY 2014
People learn about each other by looking and listening. But some information passes from person to person without either knowing it. That’s because the body can transmit signals through subtle scents. In a new study, scientists suggest that people attracted to men can pick up a manly scent coming off of guys. Similarly, a sniff may give away a woman’s gender — but only to people attracted to women.
The study suggests the human body produces chemical signals, called pheromones. And these scents affect how one person perceives another. Scientists have demonstrated the effects of pheromones in a whole range of animals, including insects, rodents, squid and reptiles. But whether people make them has been less clear.
Educators and Parents, Sign Up for The Cheat Sheet
Weekly updates to help you use Science News for Students in the learning environment
The new study’s findings “argue for the existence of human sex pheromones,” Wen Zhou told Science News. An olfaction researcher at the Chinese Academy of Sciences in Beijing, she studies the body’s ability to detect smells.
Zhou says people emit chemicals similar to those given off by animals. For example: When a female pig sniffs a chemical found in the saliva of male pig, she gets ready to mate. Men produce a similar chemical to that in their armpit sweat and hair. It’s called androstadienone (AN-dro-STAY-dee-eh-noan). Other scientists have shown that when women smell this compound, their hearts beat faster and their mood improves.
In much the same way, a chemical in women’s urine — estratetraenol (ES-trah-TEH-trah-noll) — lifts a man’s mood.
To explore the human impacts of these two chemicals, Zhou and her colleagues recruited 48 men and 48 women to take part in tests. Half of these recruits were attracted to people of their own gender or to both men and women. The scientists had all of their volunteers watch a video showing 15 dots moving around on a computer screen. At the same time, each recruit inhaled a concentrated form of one of the two chemicals. They weren’t aware of this, however. Each compound had first been cloaked with the scent of cloves, a strong spice.
The dots moving across the computer screen didn’t look like people. However, the way they moved reminded the study participants of people walking. And men who took a whiff of a female’s scent while watching the dots were more likely to rate those dots as looking feminine — but only if those men were attracted to women. Women had the opposite reaction. Those attracted to men said the dots looked masculine after a whiff of the male scent. The response of gay men was similar to that of heterosexual women: While inhaling a male scent, they thought the dots looked masculine. And women who were attracted to other women thought the dots looked feminine while inhaling a female’s scent. Zhou and her colleagues published their findings May 1 in Current Biology.
The brain recognizes gender in the scents that people give off, even when we are unaware of it, Zhou says.
But not every researcher is convinced the study settles the question of human pheromones. One doubter is Richard Doty. He directs the Smell and Taste Center at the University of Pennsylvania in Philadelphia.
“The notion of human pheromones is fraught with problems,” he told Science News. For example, hesays, the new study may not reflect the real world. The human body may excrete these compounds at such low levels that the nose won’t detect them. If true, he says, the chemicals might not drive a person’s perception as strongly as the new test suggests.
feminine Of or relating to women.
gay (in biology) A term relating to homosexuals — people who are sexually attracted to members of their own sex.
heterosexual A term for someone attracted to people of the opposite gender.
masculine Of or relating to men.
olfaction The sense of smell.
pheromone A molecule or specific mix of molecules that makes other members of the same species change their behavior or development. Pheromones drift through the air and send messages to other animals, saying such things as “danger” or “I’m looking for a mate.”
R. Kwok. “Secret signals.” Science News for Students. Jan. 15, 2013.
P. Wysong. “Cool Jobs: Scents of science.” Science News for Students. Sept. 12, 2012.
About Stephen Ornes
Stephen Ornes lives in Nashville, Tenn., and his family has two rabbits, six chickens and a cat. He has written for Science News for Students since 2008 on topics including lightning, feral pigs, big bubbles and space junk.
Classroom Resources for This Article Learn more
Free educator resources are available for this article. Register to access:
You really can smell fear, say scientists
The smell of fear, one of the most terrible cliches of pulp fiction, is actually founded in fact, scientists claim today.
People can unconsciously detect whether someone is stressed or scared by smelling a chemical pheromone released in their sweat, according to researchers who have investigated the underarm secretions of petrified skydivers.
The team found that the smell of fear triggered a heightened response in brain regions associated with fear when inhaled by volunteers in a brain scanner. The research suggests that, like many animal species, humans can detect and subconsciously respond to pheromones released by other people.
The research was funded by the US Defence Advanced Research Projects Agency - the Pentagon's military research wing - raising speculation that it is a first step to isolating the fear pheromone for use in warfare, perhaps to induce terror in enemy troops. But Darpa denied that it had any military plans for fear pheromones or plans to fund further research into the field.
Dr Lilianne Mujica-Parodi at Stony Brook University in New York State and her team taped absorbent pads to the armpits of 20 novice skydivers - 11 men and nine women - on their first tandem jump. The pads soaked up sweat before they leapt from the plane and as they fell. For comparison, the team collected sweat from the same individuals as they ran on a treadmill for a similar duration at the same time of day they had made their jump.
They transferred the two types of sweat to nebulisers and asked volunteers in a brain scanner to breath it in. The team did not tell the volunteers about the experiment. New Scientist magazine reported that the volunteers' amygdala and hypothalamus - brain regions associated with fear - were more active in people who breathed in the "fear" sweat. The volunteers in the brain scanner were unable consciously to distinguish between the two types of sweat.
In a conference presentation last year, Mujica-Parodi wrote: "We demonstrate here the first direct evidence for a human alarm pheromone . our findings indicate that there may be a hidden biological component to human social dynamics, in which emotional stress is, quite literally, 'contagious'." She declined to comment further on the results because the study is under review with a scientific journal.
Simon Wessely, a psychiatrist at the King Centre for Military Health Research at King's College London, told New Scientist that the idea that a fear pheromone could be developed as a chemical weapon was scientifically implausible. He said that a purely physiological cue was not enough to induce fear.
Most researchers do not believe that humans can detect pheromones. In other mammals this is done using a structure in the nose called the vomeronasal organ. Although humans have one of these it is not connected to the brain. However, human pheromones could still be detected elsewhere and some small studies have suggested that human behaviour can be modified by an alarm pheromone.