Women's Health Writeup: I'm only cheating cause my body TELLS me to

Sep 27 2010 Published by under Blog Carnivals, Neuroscience, Uncategorized


Welcome to my post on the Women's Health Writeup! I at first didn't see much I could do in this article on cheating (is fidelity obsolete?), but the more I read, the more I saw to write. Sci isn't an ethicist or sociologist and thus cannot really comment on the question of cheating in those terms, but she sure as heck is a NEUROSCIENTIST. And this article is all about neuroscience. Well, sort of.

Cheating Spouses: Why Both Men and Women are Straying Away from Marriage (titled in the print version "Is Fidelity Obsolete?")

Basically, this article goes through the timeline of a adulterous episode between "Sara" and "Ben" (quotations eliminated from here on out because that gets annoying). As it goes through, it gives various sociological and neurological reasons why women cheat, showing what may be going on in the brain at every stage.

But what they've got...isn't entirely accurate. So I'm going to go through this article, and talk about (to the best of my knowledge) what really IS going on the brain.

Part one: The flirtation

As Sara approached Ben that night, she felt giddy—almost as if she'd already pounded the glass of wine she hadn't yet ordered. She didn't know it, but by the time Ben pulled out the barstool next to his, invited her to sit down, and asked what she'd like to drink, the area of Sara's brain that houses her dopamine receptors (a.k.a. "the pleasure center") was lit up like the Christmas tree at Rockefeller Center. A neurochemical rush of dopamine, phenylethylamine, and oxytocin flooded her body, and she instantly felt excited. Eager. Spontaneous.

Credit goes to this author for making neurochemistry sound like a romance novel. If I could do that, I assure you my professional papers would be a lot more entertaining.

But this is where, when I read the article, warning signs started going off in my brain..."like a Christmas tree at Rockefeller Center".

Let's go through this bit by bit. The "pleasure center" they are talking about is probably the nucleus accumbens, an area of the brain associated with feelings of reward (like from drugs, sex, or rock and roll). This area does indeed have a ton of dopamine receptors, and is sometimes referred to as the "pleasure center" (though we know that's not really it, now, but I don't expect the author to know that) so spot on there. Where I started going "whaaa", was the next bit:

A neurochemical rush of dopamine, phenylethylamine, and oxytocin flooded her body, and she instantly felt excited.

Ok, so dopamine for excitation, check. But...oxytocin? Oxytocin does have effects on pair bonding, but that's usually associated with sexual activity and orgasm, not during flirting. Though oxytocin does increase what we call "affiliative behavior" which is how much time you want to spend with a person. But would oxytocin "flood your body" during flirting? Probably not, that's gonna happen later.

Finally, phenylethylamine. WTF is phenylethylamine?! Most of us know it as a drug, but it is also a trace chemical in your brain. Apparently phenylehylamine can increase the amounts of dopamine getting released in the nucleus accumbens. Which I presume would indeed increase the heady effects of dopamine...if we had any proof of this occurring during flirtation or sexual activity. We don't. Most studies on phenylethylamine refer to its use as a club drug and the related unprotected sexual activity, but I didn't find anything on flirting or extra-pair copulation, though there are increases after positive interactions between humans and dogs. The idea that it would increase during sex isn't such a stretch, but it hasn't been tested (to my knowledge), and there's no real reason I could see to even mention phenylethylamine...except that it's got a very cool sciencey sounding name.

Moving on.

In a study of women between the ages of 17 and 30, those with higher levels of estradiol (an ovarian hormone that gives a woman the physical characteristics most desired by men—think high cheek bones, symmetrical facial features, and an hourglass figure) were more likely to flirt, kiss, and have a serious affair with someone other than their primary partner than were those with lower levels of this reproductive hormone.

The article they are referring to here is Durante and Li, "Oestradiol level and opportunistic mating in women", Biology Letters, 2009.

Durante, K., & Li, N. (2009). Oestradiol level and opportunistic mating in women Biology Letters, -1 (-1), -1--1 DOI: 10.1098/rsbl.2008.0709

Basically, the study showed that women with higher estradiol levels in the peri-ovulatory and luteal phase of the menstrual cycle were correlated with higher senses of desirability and a lower relationship commitment in women. That finding is just fine, but it's not ALL. And that paragraph above doesn't really show the findings of the relationship. The main finding, to my eyes, is that women with higher estradiol levels perceive themselves as being MORE ATTRACTIVE TO MEN than women with lower estradiol levels. They may not necessarily have a desire to stray, they merely know that they are attractive. Attractive and confident women may get more flirtatious attention, and thus may be more inclined to keep their options open. The estradiol may have something to do with it, but what isn't mentioned in the article is how much attention men pay women, and how that is influenced by attractiveness and whether women are likely to cheat. If "Ben" above, isn't giving Sara the eye, she's probably not going to hop into bed with him. Is it the estradiol? Or is it the attractiveness, and the major social benefits that come with it, that are at fault here? Or is it both?

Either way, what we have here is a correlation/causation distinction. Estradiol may be CORRELATED with less satisfaction in a relationship and a willingness to stray, but estradiol may not be the CAUSATION. The article makes it sound like estradiol is the causation, and that we're being controlled by our hormones (though the article does mention exceptions to this).

specifically, how we think our partner smells. You've probably heard about the research showing that the more you like a guy's natural scent, the more dissimilar your genetic makeup is likely to be, and the more sexually attracted you'll be to him because of the high chance that you'll make healthy, good-looking babies. Well, scientists at the University of New Mexico wanted to know if partners' genetic similarity had anything to do with their sexual satisfaction too. So they studied 48 heterosexual couples who had been together for at least two years, quizzing them about their sexual histories and testing them for genetic compatibility. Sure enough, the more similar a woman's genetic makeup was to her partner's, the less she seemed to enjoy having sex with him and the more likely she was to report having had affairs.

Sadly, I couldn't find the article they were referring too (people at U New Mexico? Is that the best you can do for a citation?!), but this bit relates to the MHC complex that has been so touted among women's magazines. That you care about what your guy's sweat smells like, and that this will influence attraction. The idea is that MHC, your major histocompatibility complex, is a group of molecules that plays a big role in your immune system. The basic deal is that you want to mate with someone with a different MHC than you, so that, by your powers combined, you will make more immune babies. The great thing about this MHC is that we can actually detect it by SMELL, and thus will be able to better select a mate. That's all well and good, but it's actually a lot more complicated than that. For example, your MHC by smells prefers someone who is dissimilar, but your MHC by SIGHT prefers someone MORE similar to you. Not only that, but your preference for MHC-different dudes completely reverses when you're ON THE PILL. A large number of women these days ARE looking for mates while on the pill, and this may have an influence on who they are sexually attracted to, one which may change when they settle down and go off the pill in preparation for kids. So the MHC complex does have an effect, but that may change based on your circumstances. And of course, sexiness isn't everything in terms of long-term relationships, either.

Other studies show that some men also have more of a physiological propensity than others to pull a Tiger. Swedish researchers found that the fewer receptors for vasopressin (a neurotransmitter associated with feelings of attachment and a need to protect a partner) a man has in his brain, the more likely he is to seek sexual variety and to be disloyal. In addition, the more testosterone a male receives in utero, the higher his likelihood of infidelity, says psychiatrist Daniel G. Amen, M.D., a brain-imaging specialist and the author of Change Your Brain, Change Your Body. (Here's a clue: If your dude got a hefty dose of the hormone before he was born, his ring finger is likely longer than his pointer finger, says Amen. Go ahead—put down the magazine and check out your guy's hand. We'll wait.)

I recall this study coming out, but I cannot find it to save my life right now. I do recall that men with higher vasopressin (and thus fewer receptors) have more extra-marital sex (does anyone else remember this article? Anyone?). This is interesting, as in prairie voles, vasopressin is important in pair-bonding, and usually only to one lady at a time. But in this, the author is pretty well correct, at least as far as I can remember from the study. In addition, vasopressin DOES enhance a dude's ability to recognize sexual cues. However, this:

there's no pill (yet!) that can lower estradiol levels in a woman or pump more vasopressin into a man.

was probably silly. If a guy has FEWER vasopressin receptors (as stated above), he probably has MORE vasopressin around already. This is because the receptors respond to the levels of hormone that are in your body. If you have more hormone, less receptors are needed, while if you have less hormone, more receptors are needed to soak up every last bit of the hormone that's around. So if you have LESS, vasopressin receptors, pumping in more vasopressin is probably a bad idea. Also, if, as above, you get increased recognition of sexual cues with vasopressin, you probably want to keep that low if your guy has straying tendencies...

Thanks to our fast-paced, get-it-when-you-want-it lifestyle (e.g., instant information via a smartphone, the continuous wonder of what e-mail might await, a DVR that lets you fast-forward through commercials), we're overworking the pleasure centers in our brains. The result? It's taking more and more to satisfy us, including our sexual appetites.

The idea here is that we have so much overstimulation that we're tolerant to it, and thus require more hedonism to satisfy our lusts. I keep hearing this touted for everything from drugs to food to sex, but I haven't seen a study. I'll wait on the study.

A Side Note: The Side Bar.

The side bar in the print version of this article (not listed in the online version), cited the now very well known stripper study, which found that women made more money stripping while they were ovulating. The authors argued that this is economic evidence for male detection of the "hidden" female ovulatory cycle, and while that may be the case, a colleague of mine who studies this found some problems with this paper. For example, do women who are ovulating behave more flirtatiously and dance more...sexily, when ovulating? Some studies show that they do, and if this is the case, then it's not the men sensing the ovulation, it's the men sensing the change in female behavior. But hey, it was a scientific article about strippers, and bound to get a lot of press. Back to the article.

Turning up the Heat

Sara and Ben start taking it up a notch (Women's Health notes that she's a hottie and he's apparently gotten a lot of action). First there's a lot of stuff about social and emotional needs, and the section gets more like a romance novel:

But in the next instant, Ben's hands were on the small of her back, and he pulled her closer to him, kissing her gently at first and then with more intensity. Sara couldn't resist then—mostly because she was so turned on. Much more so than when she was with her husband.

(Can't they just have romance novel sections in these magazines? I guess people would be too ashamed).

That's because when you're with a new partner, the neurochemicals that surge through your body (for both men and women) are much stronger than those released when you're with a long-term lover, says clinical psychologist David J. Ley, Ph.D., author of Insatiable Wives: Women Who Stray and the Men Who Love Them. "As a result of the higher levels of neurochemicals, a new lover's caress is often way more stimulating than your spouse's," he says.

I really wish people would CITE this stuff. A book author is not enough. I need PAPERS. I have no idea what to even search for here, but none of it would surprise me. Novelty is a very stimulating thing in terms of reward, after all.

Ley notes that another factor at play in Sara's overwhelmingly strong attraction to Ben was an additional change happening in his body. For men, the prospect of sex with a new partner creates a physiological response that doesn't happen before sleeping with a familiar partner: Neurochemicals in their semen (predominantly testosterone and prostaglandin) rise higher, producing more semen and an ability to have longer, more vigorous sex.

I think it's interesting how they mention oxytocin in Sara, but not in Ben. Ben is experiencing a major surge in oxytocin here, at least, if he's got an erection, he is (and presumably he's got one by this point, or he will shortly). Perhaps testosterone and prostaglandin sound more manly? Otherwise, the problem here is testosterone. It turns out that only prostaglandin is associated with higher seminal volume and concentration following sex. In fact a study in stallions (heh, heh) found that testosterone doesn't change during arousal, and in fact decreases during the act itself. But testosterone sounds really manly. And virile.

Did Sara know this? No, says Ley—but, he adds, we unconsciously pick up on the complex interplay of chemicals happening in each other's bodies.

This bit plays to the idea that we can sense pheromones, the chemical factors that trigger responses in many animal species. Sadly, while animals have this, there's not a lot of proof that humans do. Our noses have lost a lot of their working power over the course of evolution, and it's possible we don't have the ability to sense pheromones at all anymore. Even whether we actually give off pheromones is in doubt.

So what is she responding to? I mean, she's obviously responding. Well. Let's see. She's had a drink. She's been flirting. He's kissing her and pulling her close and making very obvious by his behavior that she's very desirable. Adding in some pheromones at this point might just be overkill. Nothing extra needed here. But pheromones sound so good! So sciencey! I didn't let him seduce me! His pheromones did the talking and I couldn't resist! Oops, I fell! Oops, I fell again!

(I tried to find the video of Austin Powers falling over in that plane in the first movie...and couldn't).

The rest of the article centers on more sociological factors (the influence that knowing about the high divorce rate may have), and other issues. But it does end on the note that

your biology doesn't have to be your destiny. "Just because we may be predisposed to cheat doesn't mean we can't choose to be in happy, monogamous relationships," says Ley. "Whether or not you'll stray is not out of your control—and understanding the biological forces driving your attraction to other people can help you resist temptation."

This is certainly true. We have been looking into the things that make us human, that drive us to procreate, to populate, and to otherwise get it on. But if there is one thing that centuries of hardcore behavioral codes, restrictive undergarments, and those long-term happy couples who have been married for decades, it's that we are more than the sum of our chemicals. Whether cheating is biologically ingrained, or merely socially unacceptable, it IS something that is within our control.

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