Does Sex Have a Smell?

by Michael Grisafe on October 5, 2012

An Unpleasant Aroma

Image courtesy of David Castillo Dominici / FreeDigitalPhotos.net

And no, I don’t mean that disturbing musky scent you vaguely remember upon arriving home too early as a child (but just in time for years of therapy to block out the visions that followed).

I mean pheromones. A pheromone is a fairly broad class of chemicals that signal information from one member of a species to another to trigger a response.1 Sometimes a pheromone can be chemicals released into the air, while in other cases they are secreted onto surfaces for direct contact by another member of that species.

Honey bees use pheromones to signal everything from the location of food sources to plans of attack 2, and mammals like dogs and cats frequently give off pheromones that signal mating readiness 3 (as anyone with a female cat in heat can attest to via howling tomcats outside their door).

So what about humans?

Scientists have been searching for human pheromones for decades, and what role they might play in human mating behavior. Along the way they have discovered pheromones that increase human reactions to fear 4, aversive pheromones that cause male avoidance 5, and pheromones that synchronize the menstrual cycles of women that live together.6

Bee and Flower

Image courtesy of Arvind Balaraman / FreeDigitalPhotos.net

While humans don’t seem to have an easily identifiable pheromone that leads to specific reaction like other members of the animal kingdom, there are certain pheromones that appear to be closely associated certain behaviors.

One of these behaviors is a strong sexual preference among humans for people with different immune systems than their own.7 Having kids with different immune systems from their parent is evolutionarily advantageous because all of those evil little microbes that have gotten so good at attacking their parent’s immune system will have to start off at square-one with their child. Because of this adaptive advantage, some scientists believe that body odors contain pheromones with information on a person’s immune system type. This information is then subconsciously processed, making others with different immune systems seem more attractive. It’s sort of like getting a head’s up from a potential mate that your genetic material is a good match.

In addition to assisting humans in finding good genetic matches between mates, body odor may also contain information about the sexual orientation and desirability of a potential mate. In an experiment conducted by researchers in Germany, body odor was collected from potential mates (I’m assuming from some hapless graduate student) and later presented to heterosexual and homosexual individuals.8 With the exception of heterosexual women, all of the groups in the experiment showed increased brain activity when presented with odors from their preferred partners. This supports the possibility of human body odor conveying a richer array of information on mating potential than previously thought possible.

Image courtesy of Ambro / FreeDigitalPhotos.net

So what if you don’t happen to have that stinky smell of sexy that gets the opposite sex hot and bothered? Can you cheat and make up for it with a gallon of “Axe” to override your sorry smell of desperation (technically, Axe is aerosolized desperation)?

Maybe.

According to researchers in Italy, heterosexual males and females exposed to the perfume or cologne associated with their preferred sex demonstrated a higher level of attraction to pictures of opposite sex.9 The researchers took this as an indication that perfume or cologne may actually increase a person’s attractiveness a bit. However, it’s pretty hard to say that these results are generalizable, because the study used several very specific Italian brands and perfumes and colognes vary widely (but if you’re interested in trying out your own experiment during your next bar crawl, the study’s scents were Givenchy’s Pi Neo cologne and Angel and Demon perfume).

In summary, how a person smells is about as important in human mate selection as how they look. So the next time your girlfriend starts giving you the deets on how hot the guy in the apartment next door is, stop her and ask the important question: “But how does he smell?”

(Which isn’t creepy at all.)


1Hoover, K.C. (2011). The scent of emotion, sex, and evolution. Maturitas. 70, 1-2.
2Honey Bee Suite. What makes honey bees aggressive?
3PetPlace Veterinarians. Cats and Mating.
4Frey, Monika C.M., Weyers, P., Pauli, P., & Muhlberger, A. (2012). Androstadienone in motor reactions of men and women toward angry faces. Perceptual and Motor Skills, 114, 807-825.
5Gustavson, A.R., Dawson, M.E., & Bonett D.G. (1987). Androstenol, a Putative Human Pheromone, Affects Human (Homo sapiens) Male Choice Performance. Journal of Comparative Psychology, 101, 210-212.
6Wysocki C, Preti G. (2004). Facts, fallacies, fears, and frustrations with human
pheromones. The Anatomical Record, 281A, 1201–11.
7Wedekind C, Füri S. (1997). Body odour preferences in men and women: do they aim
for specific MHC combinations or simply heterozygosity. Proceedings of the Royal Society of London B Biological Sciences, 264, 1471–1479.
8Lubke, K.T., Hoenen, M., Bettina, P.M. (2011). Differential processing of social chemosignals obtained from potential partners in regards to gender and sexual orientation. Behavioural Brain Research. 228, 365-387.
9Capparuccini, O., Berrie, C.P., Mazzatenta, A. (2010). The potential hedonic role of olfaction in sexual selection and its dominance in visual cross-modal interactions. 39, 1322-1329.

[Update:  10/12/12 Edited typo in the last sentence.  Thanks for the catch, Ashley Cummings!]

Elizabeth Fryer October 6, 2012 at 9:23 am

Michael, You did a good job of mixing data with a lighter tone—so as not to overwhelm the reader. I laughed out loud when I read “technically, Axe is aerosolized desperation.”

I’m curious about “the exception of heterosexual women.” You should probably give just a sentence to sum up their results. “Their brain didn’t react ever.” Or “Their brain reacted to all scents.” Something like that.

Michael Grisafe October 6, 2012 at 2:30 pm

Hi Elizabeth,

I’m glad you enjoyed the little poke at Axe (I was at a gathering the other day of business folks and the air fairly reeked of the stuff).

I agree that I should have delved a bit more into the heterosexual woman’s response. The results here were a bit more fuzzy. In general their brain reacted more to heterosexual men AND lesbian women than heterosexual women, but the standard deviation of this measure was pretty large. I was struggling with how to say this in a simple way for those unfamiliar with stats, so I just sort of glossed over it. In the future, I will have to put a bit more thought into conveying some of the more technical results in a simple and clear format.

PF Anderson October 6, 2012 at 9:32 am

I really like this post. And, as far as constructing a science blogpost goes, it’s darn near perfect. You’re doing a lovely job of explaining complicated concepts in simple terms. What puzzles me is that in the tags, you use the complicated terms, but don’t use them or define them in the post. What you’ve done is fine, but I’m thinking this might have been an opportunity to teach new words to people, expand vocabularies, add just a tiny bit of health literacy to the post. While it might be beyond the feasible scope of this post, a thought for future posts might be a big about the disagreements in the research literature (“both sides now”), and how you determine or select the evidence that persuades you. You probably don’t really need it, I’m just brainstorming how to make a very good piece even better. :)

Michael Grisafe October 6, 2012 at 2:39 pm

Hi PF,

Thanks for reading and commenting!

I really appreciate the positive and constructive feedback. As I write my next posts I am really struggling with exactly what you are articulating here. I want to capture the interest of people who may not have extensive knowledge of science, explain concepts to them, and maybe start to educate them in a deeper way. Some of my upcoming topics are a bit more complicated, and I almost feel like I need a larger story format to encapsulate the ideas. I think I’ll try to define the more complicated terms in future posts, and will attempt to include some of the reasoning for the analysis and conclusions I make in the articles. As you know, it’s a delicate tipping point between providing in-depth coverage that really educates, and having people click off the page because the writing has become too overwhelming. I’ll definitely try to strike this balance in the future.

Michael Grisafe October 6, 2012 at 3:05 pm

Oh, and yes! If I am not discussing the technical science terms, I shouldn’t use them as keywords for SEO! I’ll definitely get the wrong audience! Good catch.

Ashley Cummings October 6, 2012 at 11:14 am

I really like this post and the topic! I think it is very well written and understandable. But what are you trying to say in this sentence… “So the next time your girlfriend starts giving you the deets on how the hot the guy in the apartment is, stop her and ask the important question: ‘But how does he smell?’” This may need revising. Keep up the great work!

Michael Grisafe October 6, 2012 at 2:48 pm

Heya Ashley,

That is my lame attempt at a joke. I sometimes forget that other people don’t live in the same crazy brain space as me. In my mind, I was addressing a woman about her female friend in the same Valley Girl lingo I picked up living in California (in which grown women often refer to their female friends as “girlfriends”). I think if I was a female writing this article, it may have been taken that way. But as it stands, it sounds like some sardonic male jealously addressing his girlfriend who is talking about a “hot guy” next door. I just basically meant to emphasize that smell and pheromones might be as important to attraction as how pleasing a person is visually. I thought it was funny, but then again, I think I may be an audience of one for this joke. Sorry if it fell flat!

Michael Grisafe October 12, 2012 at 4:04 pm

Ok, so it only took me a a couple weeks to see my typo here. I must have gone through a couple drafts and forgotten to update a couple missing words. Thanks for the catch! The sentence now reads: “So the next time your girlfriend starts giving you the deets on how hot the guy in the apartment next door is, stop her and ask the important question: ‘But how does he smell?’”

Thank you for your help!!!

Ashley Cummings October 13, 2012 at 1:05 pm

No problem. :)

number1monkeyfan October 6, 2012 at 11:38 am

I’m here again!

You need to work on the graphics on your blog mate! Smell goes a long way in making a person seem attractive to the opposite sex, graphics do the exact same thing for your blog.

Great post nevertheless, can’t fault the writing but didn’t find the topic very exciting.

xoxo

Michael Grisafe October 6, 2012 at 2:56 pm

The graphics were a bit lame, right? Man, if I only had some money to buy real graphics! Alas, I am a poor grad student, but I will try to do a better job. My original idea was to have a pic of a man or woman smelling the other’s semi-nude body. Sadly, none of my friends would agree to this moderately creepy call for models, and there was nothing that I could find like that on the net for free (hence the girl with the “stink face”). Sorry you didn’t like the topic. Be sure to check out some of my fellow student’s posts. There were some really interesting ones about
Interior Design and Health: http://www.mindthesciencegap.org/2012/10/05/interior-design-an-overlooked-health-promotion-strategy/
Star Treck Health (ok it is more than that): http://www.mindthesciencegap.org/2012/10/04/of-nanites-and-knees-looking-at-the-history-and-pop-culture-of-implants/
and stinky feet (if you want to keep the smell theme): http://www.mindthesciencegap.org/2012/10/04/bare-your-soles-to-infection/

Amy October 6, 2012 at 2:09 pm

Great article. It reminds me of this: http://www.pheromoneparties.com/

Michael Grisafe October 6, 2012 at 2:57 pm

Thanks! I LOVE that video link!! Thanks for sharing!

Elizabeth Fryer October 7, 2012 at 2:19 pm

I loved the graphic of the girl with the “stink face,” as you say. It made me smile. I think it’s placement at the top of the post, right after the “Does Sex Have a Smell?” title is perfect.

…you can’t please all of the people all of the time.

Michael Grisafe October 7, 2012 at 5:47 pm

Thanks! I suppose as long as it pleases some of the people some of the time…

Margaret October 8, 2012 at 10:55 am

Michael,
Ok, I will admit the reason I did not post sooner was because I was happily looking at all of the research you did on this subject. Reading the statistics and the types of experiments done for these results. You did a lot of amazing research here! I like the topic, but agree a little with PF Anderson, with this much research, we as the audience would love some new terminology taught to us.

Fun topic. I know that I dated at least one of my ex’s, just because he smelled so good. Too bad that does not make a lasting relationship.

Thanks,
Margaret

Michael Grisafe October 8, 2012 at 8:57 pm

Hi Margaret,

Yeah, the source material was pretty interesting. Did you have a chance to check out the fMRIs on the sexual orientation study? I’m actually interested in doing some follow-up research to see if there are documented differences in response patterns of people with different sexual orientations.

I’ll try to educate a bit on my next write-up. I don’t really have that much time to do research this week, so it will probably be focused on a single article analysis.

Sorry to hear things didn’t work out with your ex. :( Maybe you could try out one of the pheromone parties posted in the video above. :)

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