Scientists Gave Prairie Voles a Love Drug, and It Worked

What if we could do the same for humans?

Ryan Stephens/Wisconsin Department of Natural Resources/Rebecca J. Rosen

Of all the animals in the mammal class, very, very few (just three percent, according to one survey) display the romantic behavior known as "lifelong pair bonding" -- or, as it is more commonly known, monogamy. To better understand this phenomenon as it manifests in humans, scientists have taken to studying our brethren in this till-death-do-them-part project, and one of the best model animals is a tiny rodent that lives throughout the American plains known as the prairie vole.

Now, prairie voles don't live long (just a year or two) so their pair bonding isn't exactly Mr. and Mrs. Featherstone-level serious, but they do build nests together, share the work of parenting, and, also (how very human of them) cheat.

Over the years scientists have identified and studied the neurotransmitters in vole brains that play a role in their pairing behavior (oxytocin and vasopressin), and now, according to a new study in Nature Neuroscience, they have been able to "facilitate" the selection of partners by female voles through drug injections that manipulated the expression of the genes that encode oxytocin and vasopressin receptors (without either changing the underlying genes or injecting the neurotransmitters outright). The drug, Mohamed Kabbaj, one of the paper's authors, said, was "playing the role of mating," and the little voles paired off as they would normally after the deed.

Of course, vole relationships are far, far simpler than human ones (is anything as complicated as human ones?), but at a very basic sense, we know that our emotional attachment to another person isn't the work of metaphysics but chemistry. And as it's chemistry, we might some day be able to manipulate it, to pop a pill to ensure that love lasts. In a sense, we are already tinkering at the ethical edges of this, with drugs that treatment both depression and impotence proving a boon to marriages the world over.

But those uses may seem quite different than something like the human equivalent of this vole experiment. If we could, should we use drugs to make humans fall (and stay) in love? In an interview in The Atlantic last year, Ross Andersen spoke with Oxford ethicist Brian Earp, who argued that in certain circumstances it would be unethical *not* to take the drugs. As Earp reasoned:

Imagine a couple that is thinking about breaking up or getting a divorce, but they have young children who would likely be harmed by their parents' separation. In this situation, there are vulnerable third parties involved, and we have argued that parents have a responsibility--all else being equal--to preserve and enhance their relationships for the sake of their children, at least until the children have matured and can take care of themselves. One way to do this, of course, would be to attend couple's therapy and see if the relationship problems could be meaningfully resolved through "traditional" methods. But what if this strategy isn't working? If love drugs ever become safely and cheaply available; if they could be shown to improve love, commitment, and marital well-being--and thereby lessen the chance (or the need) for divorce; if other interventions had been tried and failed; and if side-effects or other complications could be minimized, then we think that some couples might have an obligation to give them a try. Of course, we aren't suggesting that anyone should be forced to take love drugs--or any drugs--against their will. But we do think that when children are involved, the stakes become higher for finding a workable solution to relationship difficulties between the parents.

Now that's still not quite the case of the voles, in which the drugs actually facilitated pairing. As to whether that would be ethical, I'd have a lot of questions about how, exactly, that would work, but, not for nothing, I can think of several well-worn strategies for finding a mate -- no pharmaceuticals necessary -- that aren't so morally pure themselves.