The Science of Attraction
- Dr. Mark W. Bland
- Mar 23
- 4 min read
Have you ever had the experience of meeting someone with attractive looks, only to decide that the “chemistry” is just not there? Or, perhaps you’ve met someone with less than striking looks, only to find them irresistible? You may be surprised to learn that sexual selection operates for humans as it does with other species and, while attraction is obviously complicated, whether or not we find ourselves attracted to someone really does come down – at least in part – to chemistry!
The attractiveness we feel towards a potential partner has been found to be linked to a gene complex which regulates the immune system, known as the Major Histocompatibility Complex (MHC). The MHC’s function is to distinguish between “self” and “non-self” as a way to regulate the immune system’s response to foreign invaders. Clearly, being able to tell the difference between our own cells and foreign matter is an important first step in launching an attack on any foreign invaders – such as bacteria or viruses – so that the immune system attack can target the invaders and leave our own cells and tissues alone. Not surprisingly, it is the MHC that generates tissue transplant rejection as well.
So what does this have to do with the sex appeal of others? Researchers have learned that variability in the MHC has a lot to do with whether we find someone attractive. The basic idea goes like this: the more differences there are in this gene complex between potential partners, the more variable these genes will be in a couple’s children, which in turn will confer a greater chance for long-term survival and healthy lifespan for them. Exactly how we are able to figure out the MHC variability of those we meet and interact with is not well understood, but it appears that we are able to detect these differences subconsciously in one another’s scent.
In one study, women were asked to smell T-shirts worn by anonymous males overnight (freshly showered, and without deodorant or cologne), and were then asked to pick the ones which were most appealing (or, smelled the best). Interestingly, women consistently selected those worn by men with a significantly different MHC as compared with their own. Moreover, this genetic difference can also be detected in saliva, suggesting that kissing may have evolved as a “taste-test” of sorts for potential partners.
There is a potential and serious downside to this, however. Women who are taking birth control pills (which chemically simulates pregnancy) tend to choose wrong in the T-shirt test. Then, when they go off the pill, their impaired ability to detect another’s MHC is reversed. It has been suggested that the pill may actually contribute to divorce: women “select” a husband or partner while on the pill, and then stop taking it to have a baby – only to realize they’ve made a mistake in their mate selection!
Obviously, MHC compatibility is only one factor in mate selection for humans. In other studies, the traits women found attractive in men have been shown to vary, depending on such factors as whether they were seeking a short-term or long-term partner, and where they are in their menstrual cycle. In general, women who are seeking a short-term partner, as well as those who are close to ovulating, prefer high-testosterone males (as indicated by a big square jaw, V-shaped torso, and deeper voice). Conversely, women in other phases of their monthly cycle, along with those looking for long-term partners, consistently found males who they considered as warm, faithful, financially successful, and with “paternal potential” more attractive.
So, what about men? Besides studies which suggest that men tend to prefer youth and beauty, it has also been learned that men also respond to the menstrual cycle of women. For example, female exotic dancers who are ovulating were found to make an average of $70/hr, while those who are menstruating make $35. And, those who are neither ovulating nor menstruating make $50. Further, dancers taking birth control pill average $37 per hour, with no performance peak, while dancers not on the pill averaged $53. That dancers who are ovulating make more than the others indirectly suggests that men are “wired” to detect when women are in their fertile phase, thus leading to more attention for them. Why there are such variations has not yet been determined, but the author of the study suggested that the dancer’s monthly cycle brought about changes in body odor, waist to hip ratios, and facial features – not to mention subtle changes in their behavior.
We have much to learn about the science of attraction, but biologists and evolutionary psychologists are uncovering new details on a regular basis. And yes, it really is all about chemistry!
Interesting reading:
Gangestad, S.W., Thornhill, R., Garver-Apgar, C.E. (2010). Men's facial masculinity predicts
changes in their female partners' sexual interests across the ovulatory cycle, whereas men's intelligence does not. Evolution and Human Behavior, 31(6), 412-
Miller, G., Tybur J.M., & Jordan B.D. (2007). Ovulatory cycle effects on tip earnings by lap
dancers: economic evidence for human estrus? Evolution and Human Behavior, 28(6),
Miller, S. L., & Maner, J. K. (2011). Ovulation as a male mating prime: Subtle signs of women's
fertility influence men's mating cognition and behavior. Journal of Personality and Social Psychology, 100(2), 295–308. https://doi.org/10.1037/a0020930.
Roberts, C.S., Gosling, L.M., Carter, V., Petrie, M. (2008). MHC-correlated odour preferences in
humans and the use of oral contraceptives. Proceedings of the Royal Society B: Biological Sciences, 275(1652), 2715–2722. https://doi.org/10.1098/rspb.2008.0825.
Wedekind, C., Seebeck, T., Bettens, F., & Paepke, A. J. (1995). MHC-dependent mate
preference in humans. Proceedings of the Royal Society B: Biological Sciences, 260(1359), 245-249. DOI: 10.1098/rspb.1995.0087.
Ziegler, A., Kentenich, H., & Uchánska‐Ziegler, B. (2005). Female choice and the MHC. Trends
in immunology, (26)9, 496-502. https://doi.org/10.1016/J.IT.2005.07.003
