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    Sadhu bjf's Avatar
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    Default Pheromones, in context

    Volume 33, No. 9 October 2002

    Pheromones, in context
    In a field plagued by murky results and marketing hype, a few things are finally becoming


    Monitor staff
    Print version: page 46

    This is a field of research

    where the opinions of experts range from gung-ho boosterism to outright skepticism, where accusations of data

    fudging and sexism fly, and where the popular press is always watching from the sidelines, ready to trumpet each new

    claim and counterclaim to the world as soon as it is made.

    On one side of the debate are the pheromone

    boosters, some of whom have founded companies that sell pheromone-based perfumes and pharmaceuticals. On the other

    side are skeptics who argue that the phrase "human pheromone" is a contradiction in terms. Between the two extremes

    lies a middle ground of researchers who are doubtful of the strongest claims but unwilling to ignore the possibility

    that humans, like many other animals, use chemicals to communicate.

    Among them is Martha McClintock, PhD,

    who can be credited with starting the human pheromone phenomenon. In 1971, the University of Chicago psychologist,

    then an undergraduate at Wellesley College, published a study showing that the menstrual periods of women who lived

    together tended to converge on the same time every month, an effect thought to be mediated by pheromones.

    Now, more than 30 years later, McClintock and others in the middle ground are finally making progress in

    understanding the effects of human pheromones. Many aspects of the field remain unclear--including the definition of

    the term "pheromone" itself (see sidebar on page 48)--but at least one conclusion can be drawn from the research

    conducted so far: Their effects are far more dependent on social and psychological context than originally


    Stop lights and sweaty underarms

    When McClintock first began studying menstrual synchrony

    in the 1970s, data addressing how one woman could affect the hormonal cycle of another was nonexistent. But it

    seemed plausible that pheromones were responsible, especially since one of the original definitions of the term

    described them as "ectohormones," substances that worked between individuals in much the same way that

    "endohormones," like testosterone and estrogen, worked within them.

    There were hints that the pheromones in

    question were associated with underarm secretions, but it took until 1998 for McClintock and Kathleen Stern, PhD, to

    show that fluids collected from a donor woman's underarms, when applied to the upper lip of a female recipient,

    could hasten or delay the recipient's menstrual period. The study fell short of identifying the exact chemicals

    responsible, but even many skeptics agree that it provides strong evidence for the existence of human pheromones.

    The pheromones thought to be responsible for menstrual synchrony are known as "primers"--substances that can

    influence long-term changes in hormone levels, such as those that take place during the menstrual cycle, the onset

    of puberty or pregnancy. But researchers were also eager to find evidence for human "releasers"--quick-acting

    pheromones that in non-human animals can trigger stereotypical behavioral responses, such as sexual intercourse.

    Although some were skeptical that any stimulus--auditory, visual, tactile or chemical--could elicit stereotyped

    behaviors in humans, others were more optimistic.

    Those researchers focused their attention on so-called sex

    attractants like androstenone, a substance found in boar saliva, and "copulins," primate vaginal secretions that

    supposedly triggered male mating behavior. When further research showed that these substances had mixed or minimal

    effects in humans, however, excitement within the scientific community died down. But interest continued outside the

    scientific community, and some researchers founded companies to develop and market pheromone-based products intended

    to boost self-confidence or sexual attractiveness. Two of the substances that received the most attention were the

    hormone-like chemicals androstadienone and estratetraenol, which are found in human sweat.

    "The idea was

    that men produce androstadienone and that's a sex attractant to women, and women produce estratetraenol and that's

    a sex attractant to men," explains McClintock, who is critical of the claims made by many commercial pheromone

    companies. "Then they backed off from the sex attraction and modulated it more, to say, 'Well, it just makes you

    feel more self-confident and open to social communication.'

    "We have found that these compounds do have

    very interesting effects on psychological state and brain function," she adds, "but it's not the simple picture

    that was originally portrayed."

    In 2000, McClintock and then-graduate student Suma Jacob, PhD, now a medical

    resident at the University of California, Los Angeles, reported that androstadienone and estratetraenol's effects

    on behavior were both sex- and context-dependent. In one experiment, the chemicals improved women's mood but had

    the opposite effect on men; in another experiment, they kept women's mood from deteriorating over the course of the

    testing session, but didn't improve it. McClintock and Jacob concluded that if the substances were indeed

    pheromones, they were modulators, not releasers--substances that affect behavior by altering psychological state,

    not by triggering fixed responses.

    Meanwhile, researchers like Winnifred Cutler, PhD, one of those who

    founded companies to market pheromone-based perfume additives in the 1980s, were trying to show that the substances

    worked as advertised. In 1998, she reported that her male perfume additive significantly increased men's likelihood

    of having sex. Last spring, San Francisco State University psychologist Norma McCoy, PhD, reported similar results

    using Cutler's female perfume additive.

    In McCoy's view, their studies show that the pheromones work under

    real-world conditions, regardless of laboratory results. "I think that we've once and for all demonstrated that

    this pheromone, however it's constituted, does have powers over the other sex," she says. "There is something that

    makes women attractive, and it can be very, very powerful."

    Charles Wysocki, PhD, of the Monell Chemical

    Senses Center, disagrees. "There's no good evidence in the biomedical literature that these are human pheromones,"

    he says. According to his analysis of McCoy's data, the additive appeared to work only because women who received

    the placebo and the "pheromone" started out with different levels of sexual activity, then regressed toward the

    mean--a statistical flaw disguised by the study's data analysis methods.

    McClintock, too, remains

    skeptical. Social and psychological conditions are important mediators of pheromonal effects, she says, and any

    claims that a particular product will increase the user's opportunities for sexual intercourse regardless of

    context are, in her opinion, misleading.

    "It's like saying that if you see a red light, you cannot control

    yourself from stopping no matter the circumstance," says McClintock. "Human behavior just isn't like that in any


    A dead-end duct?

    The debate over whether pheromones affect human behavior is hardly over,

    but at least enough evidence has been collected that a consensus has emerged on some effects, such as menstrual

    synchrony. In contrast, the biological details of how pheromones affect humans remain "a total mystery," according

    to Cornell University psychologist Robert Johnston, PhD, although a few tantalizing clues are beginning to emerge.

    In 1999, Noam Sobel, PhD, and his colleagues at Stanford University used functional magnetic resonance

    imaging to show that the human brain responded to androstadienone even when subjects were unable to smell it, a

    result confirmed in a later study by Jacob, McClintock and their colleagues. In 2001, Ivanka Savic, PhD, and her

    colleagues at the Karolinska Institute in Sweden reported that androstadienone and estratetraenol affected men and

    women's brains differently: The former boosted hypothalamic activity only in women, while the latter increased

    hypothalamic activity only in men. The hypothalamus influences the pituitary gland's release of hormones, so it is

    in a key position to affect reproductive behavior.

    Despite these suggestive neuroimaging results, it remains

    unclear how the presence of pheromones is communicated to the brain. In many animals, a pair of tiny ducts in the

    nasal septum called the vomeronasal organ (VNO) is responsible for detecting pheromones, but the evidence for a

    working human VNO is mixed at best. Because the main olfactory epithelium, where ordinary smells are detected, can

    also detect pheromones in some animals, the absence of a VNO would not rule out the possibility of human pheromones.

    But its presence would be a major support for the pheromone boosters.

    In a series of experiments in the

    1990s, researchers at the University of Utah claimed to have shown not only that the human VNO existed, but that

    adrostadienone and estratetraenol elicited different electrical responses in the VNOs of men and women. The result

    parallels that of Savic's neuroimaging study and, if true, would provide for a pathway for pheromones to influence

    the brain. However, because the Utah group is also heavily invested in a pheromone-based pharmaceutical company,

    many researchers are skeptical of their results, especially since no one has yet discovered a functional nerve

    linking the VNO to the human brain.

    "I don't see any serious scientific flaws in the experiments they've

    published, but then again, they haven't published everything they've done," says Michael Meredith, PhD, a

    professor of neuroscience at Florida State University, who recently reviewed the evidence for the human VNO. He

    concluded that the evidence remains equivocal, and that only further research--by other groups of researchers--will

    resolve the debate. Bernard Grosser, MD, chair of the psychiatry department at the University of Utah, acknowledges

    that a pathway from VNO to brain remains to be found, but he says he is confident that one exists. "Anyone who has

    gone in and duplicated the work we've done has found essentially the same results," he says.

    In some ways,

    the VNO question is a distraction from the main issue, which is how pheromones affect human behavior. Knowing the

    answer to one question tells you very little about the other, says Sobel, now a professor of psychology at the

    University of California, Berkeley. Ultimately the question of whether there is such a thing as a human pheromone

    will depend on tying specific chemicals to specific neural, behavioral or psychological responses--and on coming to

    some agreement about what a pheromone is in the first place.

    Future research

    Future studies may

    settle some of these controversies. McCoy hopes to extend her work on sex pheromones to postmenopausal women.

    McClintock intends to study the influence of odors given off by breast-feeding women on the fertility of other

    women. Meredith, Johnston and others plan to continue studying the biological mechanisms by which chemical messages

    affect social behavior in rodents and other animals.

    How important these substances are in everyday life

    remains an open question. But whether or not one believes that human pheromones are sex attractants, as McCoy and

    Cutler do, there are still a number of social domains in which chemical messages could have an important effect,

    says McClintock.

    "In animals, [pheromones] are involved very strongly in care of offspring, in recognizing

    members of your social group, in recognizing family members," she says. "In thinking about what the normal function

    might be, we know from the animal work that we need to think broadly in social terms and that the same compound

    might serve differently in different contexts.

    "The field of physiological or biopsychology typically looks

    at how biology causes changes in behavior," she adds. "What we're trying to do is say that that's a very

    reductionist approach, and what is really important is to realize that psychology and social interaction also

    regulate the biology."

  2. #2
    Doctor of Scentology DrSmellThis's Avatar
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    Thank you for that post! Is

    this good for the research section, do you think?
    DrSmellThis (creator of P H E R O S)

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