October 11, 2004
Breastfeeding Women Secrete Aphrodisiac Chemosignal

University of Chicago researcher Martha McClintock and colleagues have found that

Breastfeeding women and their infants produce a substance that increases sexual desire among other women, according to research at the University of Chicago.

"This is the first report in humans of a natural social chemosignal that increases sexual motivation," said Martha McClintock, the David Lee Shillinglaw Distinguished Service Professor in Psychology at the University, and the lead researcher in a team at the University's Institute for Mind and Biology. Chemosignals are substances that while not necessarily perceived as odors, nonetheless have an impact on mood and menstrual cycles when absorbed through the nose.

The researchers found that after being exposed to the breastfeeding compounds for two months, women with regular partners experienced a 24 percent increase in sexual desire as reported on a standard psychological survey. Women without partners experienced a 17 percent increase in sexual fantasies after exposure for the period.

Women in the control group with partners who were exposed to a neutral substance reported an insignificant decrease in sexual desire, while women without partners in the control group experienced a 28 percent decrease in fantasies.

The work on sexual desire is reported in the paper "Social Chemosignals from Breastfeeding Women Increase Sexual Motivation," being published in the latest issue of Hormones and Behavior.

Joining McClintock in writing the paper were Natasha Spencer, Sarah Sellergren, Susan Bullivant and Suma Jacob, researchers at the University of Chicago, and Julie Mennella, a scientist with the Monell Chemical Senses Center, in Philadelphia. The study was conducted both in Chicago and Philadelphia.

In Philadelphia, Mennella recruited 26 breastfeeding women, who were asked to eat a bland diet to avoid transmitting odors such as curry through the breast milk. The breastfeeding women wore pads in their nursing bras, where the saliva from their infants in addition to their own perspiration and milk was collected. They also wore pads secured by underarm shields to collect perspiration.

The pads were collected, cut in pieces and frozen. Other studies in the McClintock lab have shown that the procedure is effective in collecting chemosignals.

In Chicago, the researchers recruited about 90 women between the ages of 18 and 35 who had not born a child. The women were divided into two groups, one group exposed to the pads with breast feeding substances, and the other group exposed to pads with potassium phosphate, a substance that mimics the concentration of the sweat and breast milk.

"Because preconceived ideas about pheromones could potentially influence their responses, study participants were blind to the hypotheses and the source of the compounds," Spencer said. "The study was presented to the subjects as an examination of odor perception during the menstrual cycle."

Participants were given a set of pads on a regular basis and asked to swipe them under their noses in the morning and at night and any other time of the day in which they may have wiped their upper lips, showered or exercised.

The women with partners were asked about their moods and were asked to complete daily a survey with a scale indicating "the degree you felt desire today for sexual intimacy." They also recorded their sexual activity. Women without partners were also asked about their moods and reported whether they experienced "any fantasies/daydreams today of a sexual or romantic nature." Among women exposed to the breastfeeding substance, "The effect became striking during the last half of the menstrual cycle after ovulation when sexual motivation normally declines," McClintock said.

From the abstract:

Here, we demonstrate that natural compounds collected from lactating women and their breastfeeding infants increased the sexual motivation of other women, measured as sexual desire and fantasies. Moreover, the manifestation of increased sexual motivation was different in women with a regular sexual partner. Those with a partner experienced enhanced sexual desire, whereas those without one had more sexual fantasies.

Suppose this compound is identified. How it gets used will depend on how rapidly it works. If it works rapidly then expect guys to wear it as a perfume. If it takes a few hours to work then guys will want to go on longer dates to allow more time for it to take effect. If it takes days then it will be a lot harder for a single guy to use it for his own benefit. However men in longer term relationships or even men travelling with women on extended business trips would have obvious incentives to use it.

Will women want to use such a compound on themselves? That depends in part on whether it just enhances desire to have sex or does it also enhance the pleasurability of the sexual experience?

Also, some women will want to defend themselves against having their sex drive manipulated by someone else without their knowledge. One way to do that defense would be to develop compounds that block the effect of whatever compound(s) that will be isolated and found to be involved in this effect. However, another line of defense is detection. Imagine a chemical strip that is designed to react only to the aphrodisiac. A woman could wear such a strip as, perhaps, a ribbon tying up her hair or somewhere else inconspicuous and then she could check whether the strip changed color while she was sitting in a bar or restaurant.

A growing knowledge about what increases and decreases sexual drives is inevitably going to be used in the war between the sexes. Whether the net increase in knowledge will end up being used more by the offensive or the defensive or perhaps only under negotiated peace treaties remains to be seen. My guess is all of the above.

Share |      Randall Parker, 2004 October 11 03:59 PM  Brain Appetite

Michael Vassar said at October 12, 2004 7:31 AM:

The biggest beneficiaries, if it works fast, may be the early-adapter owners of bars, dance-clubs, and other places which are substantially mate-search facilitation zones. They could produce much larger exposures than a perfume would be likely to, and the increased popularity of their establishments would much more than pay for it.

Hans Gerwitz said at October 12, 2004 9:05 AM:

Even establishments would need a relatively fast-acting compound, though. I expect it to require prolonged exposure. If simply puffing a compound under the nose of a woman made her want to mate, men would have evolved a gland for it ;-)

I could see it being used to lace pillowcases, for example. Maybe it will be the foundation of a new, subtle eugenics... particularly if an "anti-aphrodisiac" is developed. I wonder if there are indirect effects; imagine if it caused shoppers to increase their purchasing of cosmetics, fashionable clothing, etc.

Engineer-Poet said at October 12, 2004 10:56 AM:

This could also explain one way that women entering the workforce decreases fertility; they are less exposed to lactating women and don't have the stimulatory effect on their libido.

Andrew McManama-Smith said at October 12, 2004 3:43 PM:

Hahah, that's way out there man!

Engineer-Poet said at October 14, 2004 3:55 PM:

Another possibility is use of pheromone antagonists by parents and schools.  Keeping one's daughters and female students from getting pregnant before they graduate, perhaps with antagonist sprays in classrooms or bedrooms, may be one way to reduce the odds of them winding up as unfortunate statistics.

brian donovan said at October 14, 2004 9:38 PM:

Thanks for posting this. Very interesting, although I confess to being a bit creeped out by the details at first. Just FYI, in case you didn't know, the complete paper is online at http://www-news.uchicago.edu/releases/04/041006.chemosignals-paper.pdf.

ClarissaB said at October 18, 2004 7:53 PM:

No doubt that this article is interesting; however, is it really necessary. Researchers spend their time and money on sexual desires of women in the midst of breast feeding. By finding this out we now know that women who want to increase their sexual desire should seek out breast feeding. Or women without children should sniff other women and their children's saliva and breast milk. Please inform me on the importance of this information. People today have to separate what information is just junk to the brain and which one is knowledge.

Rootshell said at October 19, 2004 3:21 AM:


It could be argued that such research might capture the imagination of men somewhat more than women. Further its monetization, whether the compound is fast acting or not, would be fairly straight forward. Combine sex, money and imagination in the minds of men and what's "necessary" becomes not nearly as important as does necessity being the mother of invention.

Rootshell said at October 19, 2004 3:36 AM:

...and of course the Luddite in me says that if we developed only what was necessary our lives would be much, much simpler. Stare at your hair dryer for a minute and get back to me.

Carl Ratner said at November 20, 2004 3:56 AM:

If you read the article you'll see that there was minimal increase in sexual desire and fantasies, and no increase at all in sexual activity. Even the highly sanitized conditions of directly smearing the liquids under women's noses only led to an increase of 3 sexual fantasies a month. In real life, the scents will be masked by odors in the environment and will not be applied directly to women's noses. So there will be zero affect on sexual desire and fantasy, and continued zero effect on sexual activity. If you want to understand sexual desire and activity the place to look is cultural artifacts such as cologne, clothing, make-up, sexual images in media.

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