Research on infidelity consistently suggests that about 15 percent to 20 percent of American adults, male and female alike, engage in sexual infidelity at least occasionally. Men who cheat are often lauded for their sexual conquests, referred to as "studs" and "players" by their friends. Meanwhile, women who cheat tend to be socially denigrated as "sluts" and "nymphomaniacs." Either way, the behavior is profoundly damaging to a supposedly monogamous long-term partnership -- violating trust and decreasing the emotional connection between the two partners.
So why do we cheat? In truth, there are countless reasons that men and women cheat on their significant others. And based on recent research, it appears that one of them may involve a person's genetic makeup. (That odd noise you just heard is millions of cheaters worldwide wiping their brows and absolving themselves of responsibility for the pain they've caused their spouses.) In short, certain genetic variations may influence the ways in which people process and/or respond to various neurochemicals -- most notably vasopressin, oxytocin and dopamine (all of which are released before, during and/or after sexual activity). And this in turn many influence a person's propensity to cheat.
My favorite research on genetics and infidelity involves not humans, but voles. (Voles are tiny rodents that look a lot like mice, only rounder, fuzzier, and infinitely cuter.) One well-known vole study focuses on the difference between prairie voles, which are known to be monogamous, and montane voles, which are highly promiscuous. The study links these very different mating behaviors to the ways in which vasopressin is processed in the brain. (Among other things, vasopressin affects socialization, sexual motivation and pair-bonding.) Essentially, in prairie voles, the vasopressin receptors are located near the nucleus accumbens (commonly referred to as the "pleasure center"). So in prairie voles, vasopressin stimulates the pleasure center, thereby creating and reinforcing the desire to attach and become monogamous. In montane voles, however, the vasopressin receptors are located elsewhere in the brain, and this neurochemical reward linking sex and long-term attachment doesn't exist. Hence the promiscuity. Further research tells us that it is possible to manipulate vasopressin levels in male montane voles in ways that transform them into family-centric partners and fathers, similar to their prairie vole cousins. The same is true for female montane voles, but it is oxytocin -- a hormone linked to emotional intimacy and maternal bonding -- rather than vasopressin that needs to be manipulated.
Of course, it's not just rodents that seem genetically predisposed to either monogamy or non-monogamy thanks to genetic variants affecting vasopressin and/or oxytocin. One study of humans looked at the link between promiscuity (but not necessarily infidelity) and variants of both vasopressin and oxytocin receptor genes, finding a significant relationship between five different variations of the vasopressin receptor gene and promiscuity among women (though not among men). The research team did not find a link between oxytocin genes and promiscuity. And,according to the researchers, it is not immediately clear why the relationship between vasopressin and promiscuity exists in women but not men.
Nevertheless, experiments in which vasopressin and/or oxytocin are intentionally administered (usually via nasal spray) to humans appear to increase both trust and social bonding. This suggests a few potentially useful applications. For starters, there is evidence that intranasal oxytocin can reduce the antisocial effects of autism. On the flip side, it is possible that people with Williams syndrome, a rare genetic condition that causes oxytocin levels to sit at roughly triple the normal amount (causing these individuals to be overly trusting, often to their detriment) might effectively be treated with drugs that block oxytocin production and/or reception. And of course these sprays could also, at least potentially, be used as a way to promote partner bonding and therefore marital fidelity.
It's not all about vasopressin and oxytocin, of course. Other genetic variants are also in play, including those affecting the production and/or reception of dopamine (a neurochemical that directly stimulates the brain's pleasure center). For example, a study of 181 healthy young adults found that, in general, people of both genders with a specific dopamine receptor subtype (the D4 receptor) are significantly more inclined toward non-monogamy. Essentially, this genetic variant reduces the impact of dopamine, leaving these individuals desiring (perhaps needing) more stimulation and novelty -- thereby increasing their tendency to seek out a "bit of strange."
So does this research give cheaters a genetically driven free pass? No, it does not. The fact that there is a correlation between certain genetic variations and promiscuity does not mean these genetic permutations automatically cause sexual infidelity. For an analogy, consider alcohol. Plenty of people are genetically predisposed toward alcoholism, but not all of them become alcoholic because there are many other factors in play. The same is true with a genetic predisposition toward promiscuity. Other factors are in play, including vows of monogamy.
When tempted to stray (for whatever reason, including genetics), upholding a vow of monogamy can be viewed as a personal sacrifice made toward strengthening the emotional bond (or at least toward not hurting a loved one). So even though humans cannot (yet) choose or alter their genetic coding, we are (except in a few extreme instances) able to decide what we want to do with that coding. So do we give in to every little impulse? Or do we place value on more than just what seems fun and interesting in the moment? Despite genetic predispositions, the choice is ours to make.
Robert Weiss LCSW, CSAT-S is Senior Vice President of Clinical Development with Elements Behavioral Health. As a well-known subject expert on the relationship between digital technology and human sexuality, he has served as a media specialist for CNN, The Oprah Winfrey Network, the New York Times, the Los Angeles Times, and the Today Show, among many others. Weiss writes a blog on addiction and is author of numerous books, including Closer Together, Further Apart: The Effect of Technology and the Internet on Parenting, Work, and Relationships (co-written with Dr. Jennifer Schneider). For more information, please visit his website.