Wednesday, January 31, 2007

A Genetic Test for the Likelihood of Cheating?

Psychologists at the University of New Mexico recently reported on the results of a study that shows how genetic similarities between partners are predictive of sexual responsiveness and cheating, according to this NewScientist article. The team focused on specific genes belonging to the major histocompatibility complex (MHC), analyzing 48 heterosexual couples who had been in an exclusive relationship for at least two years. The participants were asked about their sexual responsiveness towards their partner and their unfaithfulness in the relationship.

The results show that MHC genetic similarities dramatically affected the women. They were less sexually responsive to their partners, more likely to have affairs, and more attracted to other males, particularly during fertile days of their menstrual cycles. In relationships where MHC genetic differences were significant, these potentially relationship-splitting behaviors were either absent or greatly reduced.

The fraction of MHC genes shared directly correlated to the woman's number of adulterous partners – if the man and woman had 50% of the MHC genes in common, the women had a 50% chance of cheating with another man, on average.

Men did not seem to be affected by the MHC similarities. The men's average sexual interest for their partners was the same regardless of genetic similarities or differences, and the same was true for their interest in women outside of their primary relationship.

The results were so predictive for the women that there has been talk of developing a genetic test to determine how likely a woman is to be faithful to a specific partner.

Is it just me, or do others find that a scary concept?

The study results make sense when you think in evolutionary terms. Every species is more likely to prosper when there is plenty of genetic diversity. I just think the idea of a compatibility test makes the whole dating process a bit too clinical for my taste. What do you think?


  1. Hi Andrew,

    I've been meaning to reply since you commented on my Thurs. 13 post last week. I read a couple posts on your site and like what you're doing. For what it's worth, I was a psych major in college.

    Yes, I agree. Messing with genetics is usually 110% scary, I particularly don't care for scientists changing genes in foods. I have never had an affair, nor has my husband, in almost 18 years of a great marriage (it feels like much less time, but it can't be because our boys are almost 17 and 11.5!), and this test sounds like a genetic pre-nuptial agreement. "Hey babe, I love you, but before we get married I just need you to take this little test." ;)

  2. Good morning Andrew,
    Very interesting study. I think MONOGAMY is crucial, so it wouldn't bother me a bit to have that test applied to dating. I just wish there was a genetic one for guys faithfulness likelihood as well. Even if the chemical is different than the MHC. Would certainly possibly prevent a lot of heartbreak.

  3. Genetic tests in general scare me, though I am the mother of a child with Down Syndrome, so maybe I'm a little bit biased.

    Thanks for your comment on my blog the other day. Out of curiousity, how did you find me?

    Look forward to reading more of your stuff!

  4. my god - tell me this is not so...

    it takes the whole fun outta finding a mate..

    and the problem i see with genetics is that, even though people beileve them to be 100 percent -- genetic testing is not!

  5. Part of me thinks it's freakish but most of me thinks it will never catch on. For one thing, from what I've seen and how I've seen it reported in the news, the average American doesn't seem to understand the nature of genetics well enough put this in context. For another, there are too many other variables. Anyone who would put that much stock in a single test probably has enough relationship insecurity to overpower even a genetically compatible result.

  6. Anonymous2:44 PM

    Funny thing about talking about cheating, I believe it lays the foundation to do it. To be entertained by, or give validity to a study about cheating, means the person interested has thought about it, After nearly thirty years of marriage, my wife and I still believe that sexual infidelity is the only deal breaker in a marriage. So we look and dont touch, we stay focussed on each other and look at cheating like a drink to a sober alcoholic, it just ain't done. Scientific studies that try and deal with matters of the heart are just dumb, what does science have to do with genuine love? 'Nough said!

  7. Ew! This is extremely creepy to me! Someone up above in the comments said it sounds like a pre-nup agreement possibility and it does. Of COURSE women are going to have a genetic disposition towards multiple mates...WE ARE MAMMALS! We are biologically wired to seek out additional mates. The thing that sets us apart from the wilderness animals is the fact that we can produce rational thought. The genetic test may show a woman is likely to cheat genetically, but it certainly won't be able to measure her heart and her committment to her man. Only time will tell that.

  8. Andrew,
    I agree,way to clinical. Just because we are geneticly predisposed to something does not make that our reality. My thought is that if a person knew they were perdisposed to cheating, then they now have a built in excuse and will most likley fullfill this finding.
    Very dangerous road to go down.

  9. Like most studies, I think the sampling is too small and exclusive. Part of the problem is that it was only 48 couples which makes the conclusions reached anecdotal and not scientifially valid. Another part of the problem is the couples were all college age and you cannot generalize results derived from college kids to the entire population.

    In college, people tend to be more shallow and desire to experiment more (and therefore more likely to cheat). They also feel less inclined to be in permanent relationships and work at them by building a solid foundation of communication. As you get older, things like "sexual responsiveness" will come secondary to other relationship concerns (like attentiveness, respect, communicativeness, etc.).

    For such a study to even begin to have any validity, they would need to do similar testing on a much larger cross-section of the population and they would need to focus on married couples. This seems like just another one of those studies where the researchers wanted to find a specific result and found what they wanted to find. I wouldn't take it seriously at all.

  10. We can't start applying probable likelihoods to individuals, it would just result in an unfair stereotyping. Populations genetics tell us many Kenyans are amazing runners, should we tell them to get their own race because the Olympics will become too lopsided?

    In any case, we can't let any genetic inclination dictate our lives or give us excuses. Just because someone might appear more likely to cheat, doesn't mean they will cheat, and it wouldn't make it more forgivable. We're still in control of our actions. As for the tests, relationships need to be built on trust. A test would only create unhealthy, destructive suspicion or, conversely, foolish overconfidence.

  11. Hi Andrew

    I found this interesting for a different reason. I'm into serious astrology (and no, that is not an oxymoron!)

    The thought that a gene which controls sexual fidelity could be pinpointed made me wonder if there might be any correspondence between that and astrological indicators for the same trait. It would be interesting to have the birth data of those sampled !

    Ann (Twilight from Learning curve on the Ecliptic)

  12. Hi, Andrew. I think blaming infidelity on genetics is nothing more than a cop-out. It's that simple. This is just one more example of people being unwilling to take responsibilty for their own behaviour. This is a glaring example of 'group denial'. How convenient for cheaters!