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
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.
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)?
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!]