Chemical reaction

A recent study published in the prestigious journal, Proceedings of the National Academy of Sciences, showed that female rats liberally plied with the active ingredient in marijuana, THC, became more receptive to the sexual advances of their male peers. Perhaps cannabanoids go straight to the soul and induce true-rat-love in the female, who falls hard for her beau. Or so we’d like to believe. Marijuana actually just swims for part of the brain’s reward pathway, and its effects are compounded when it comes into blissful contact with effect-enhancing female sex hormones. The process is really nothing more than a series of chemical reactions, gradients and electrochemical potentials.

Hardly romantic, but we’re still convinced that love will save the day. In fact, over the course of human history, we’ve cooked up a steamy assortment of mythology surrounding love: volumes of scholarship, literature, and quotations on what it is and why we bother.

Some of these aphorisms are quaint and almost plausible. Serious-minded commentators, like French romantic writer George Sand, have only nice things to say: “There is only one happiness in life, to love and be loved.” Though that seems to discount the possibility of enjoying happiness that comes instantiated by, say, a Sno-Cone or sumptuous Moon Pie, this attitude does reflect a more or less typical view of love for the average human. Even notable skeptics who are going to sizzle on the grills of hell for their heathen atheism scorn not love. “To fear love is to fear life, and those who fear life are three parts dead already,” Bertrand Russell says. How exactly he decided that fearing love led to being “three parts dead” is a bit opaque, but you get the idea.

Love is an institution not peculiar to human beings, and has roots that extend back into our animal past. Even as far down the mammal chain as whales and dolphins, one finds behaviors that might be labeled love by a brave observer. Dolphins will buoy a wounded comrade so it can breathe, and elephants show signs that are best described as “anguish” or “grief” at the death of a friend, going so far as to cover the body with sticks and grass. And as far as romantic love is concerned, it is not uncommon in nature to find pair-bonding (where couples stay together for life) in some species.

But within our own, some have rebelled against the pull of love. Journalist H.L. Mencken found it to be “the triumph of imagination over intelligence”; the father of the Peanuts comic strip George Schulz commented on how unrequited love “takes the taste out of peanut butter”; and the creator of the Simpsons, Matt Groening, thinks that “love is a snowmobile racing across the tundra and then suddenly it flips over, pinning you underneath. At night the ice weasels come.” As is generally the case, these skeptics come closer to hitting the mark without actually hitting it.

Yet neither skeptic nor romantic sees love as does modern science—an interaction of chemical messengers in the brain’s reward circuitry, namely the nucleus accumbens and caudate. Few are willing to admit that this process is a devious method devised by natural selection to promote the replication and perpetuation of genes, often at the expense of our happiness. It may seem incredible, but even loneliness, jealousy and depression—the dark sides of romantic love—are mechanisms activated to stimulate changes in our behavior and make us more likely to mate successfully with members of the opposite sex. The fleeting joys of love and intercourse are in many ways dominated by a lifetime of unpleasant feelings (dictated by neurochemistry, of course) whose purpose it is to provoke us to seek intercourse and neurotically fight for increased status or anything else that might yield an edge in the mating game.

We’d like to deny that the defining elements of love are shallow, that the questions that are ultimately swimming through our heads have more to do with subconscious calculations about the quality of our proposed partner’s genes than with anything else. But the cues by which we make these judgments are largely superficial, inscrutable to rational analysis, and rapid. Modern theories of cognitive science propose a wide array of these subconscious behaviors whose mechanisms cannot be analyzed by our rational, sequential analytic processors. Think reflexes: You can’t consciously stop the “startle” response when you hear a gun shot, for instance. And as noble as it is to think that one would be capable of loving someone whose face was ripped off by the east-west bus, it is almost impossible that, if you did not know them before, you would become romantically involved with them. This has to do with a snap judgment of “bad genes” that is made by one of your sub-processor modules upon seeing this individual. These hidden processes heavily influence a considerable measure of our actions, and some scientists claim to have found that something as historically ignored as smell plays an important part in defining human attraction.

 

Dr. Davidson toys with his pen like a large Scottish cat. “The idea is that tolerance is not specific to drug abuse; it can be any phenomenon. People become tolerant and adapt to the constant flow.”

That probably accounts for the law of diminishing returns from sex, and why the national divorce rate flirts with 50 percent. After a while, the same behavior—or maybe the same partner—doesn’t hold the same sparkle it did before. The lesson from this of course is to have sex in the library, using the novelty of the experience to elicit an overwhelming dopamine release.

But this also has a happy upside. If the jollies one gets from lovemaking diminish with chronic exposure, then those of us who have episodic sexual encounters can take heart from another phenomenon often observed in drug abusers: sensitization. It is possible that if one has sex infrequently enough, then those encounters will be infinitely sweeter and more overwhelming when the citadel finally is sacked (think back for a moment on the effulgent sparkle of YOUR FIRST BREAST). In fact, if one has sex infrequently enough, then each successive encounter will be more powerful than the last. “If someone is forced to have sex ten times a day for a month and then presented with a receptive female the next day he would prefer to watch TV. But if someone only has sex once a year, they would jump on the person. There is an analogy between this and the drug abuse literature,” says Dr. Davidson.

When asked whether his rats fall in love, Dr. Davidson is evasive. “That will be a difficult concept to test,” he says. “Well, you know the part of the brain in humans related to these emotions, the amygdala; rats have a large amygdala but it’s certainly hard to test without asking the animal.” Yet Mr. Squeaks seldom speaks, and when he does it’s generally profane.

“Love is the brain’s way of tricking people into being monogamous,” he adds. Now that seems believable—judging from the size of human testicles (closer to those of the promiscuous chimpanzee than the gorilla) humans are at best selectively monogamous. Could it be that we convince ourselves that love is something real to promote more stable relationships?

Dr. Davidson would say so. “Marriage has helped people avoid fighting over mates,” he says.

Yet arguments like his, though perhaps slightly more primitive, haven’t stopped luminaries of the likes of Plato and Aristotle from effusively praising love. What we have here is more than just a mistake in thinking; in fact it’s probably adaptive to believe in love, in the mystique and mythology, perhaps because it helps us rear our children and stay together during the process, providing one another with support and encouragement.

The reluctance of many people to think about human behavior in scientific terms mystifies some scientists, but not Dr. Davidson. “People like to think that they are special,” he says. “If we are just a collection of atoms complying with the laws of physics, that doesn’t make us special does it?”

 

Although a post on www.ratemyprofessors.com describes Dr. Warren Meck as a “nutcase… amusing, but in a scary psychokiller kind of way,” I am undeterred. Dr. Meck, a professor in the psychological and brain sciences and director of Duke’s undergraduate program in neuroscience, agrees to talk with me about romantic love. He’s sitting in a spacious, sunny office festooned with lots of books and phrenology bobble-heads.

Dr. Meck says the hormones oxytocin and vasopressin have been of particular interest to scientists studying love. A recent paper in Nature has shown that promiscuous voles become chaste and monogamous after extra V1a vasopressin receptors have been added to the ventral palladium bit of their forebrains.

Apparently, in 1998, neurobiologists convened to talk about love in a frigid Scandinavian country, presumably so that heat-provoked romantic passions wouldn’t distract them from the task at hand. Dr. Meck pulls up the website on his chic Macintosh widescreen. “This research involves people who normally have zippo to say [about love] but may study maternal behavior in rats and voles. They study what forms the bond between mother and offspring, and look for neurochemicals released by the hypothalamus during the birthing process.”

Though, according to Dr. Meck, conference organizers told scientists to “take the stuff you usually don’t extrapolate to humans and let your hair down because you’re in Sweden at a special conference,” he warns against the perils of taking discoveries from animal research and applying them willy-nilly to humans. “In animals there is a tight chain of stimulus response,” he says. “Humans forever break this chain.”

Indeed we’re complicated, culture-bearing creatures. Craven democrats might even call us nuanced. Dr. Meck, however, is not entirely satisfied with the dopamine, oxytocin, and vasopressin model of love, surmising that there is much more to Cupid’s elixir. As an example, he refers me to a paper published in the International Journal of Neuroscience in 2003, which found that people who had a tendency to “fall in love,” as measured on the “Passionate Love Scale” questionnaire, produced less digoxin, a chemical secreted in the hypothalamus (a region involved in sex) that regulates neuronal signaling (Kurup and Kurup 2003). Perhaps these loving individuals have cells that are more easily influenced by the chemical soup (dopamine, oxytocin, vasopressin, opiates, et al.) produced in the process of falling in love and are therefore more susceptible to Aphrodite’s caress, again, oh yes, and again.

“I’m surprised [other researchers] don’t talk about opiates being involved in love,” Dr. Meck adds, eyes closed adorably. He notes that while pleasurable reward is a combination of dopamine and opiates, popular psychology is reluctant to acknowledge the importance of opiates due to their dangerous association with such social taboos as heroin. “Psychology Today only relies on dopamine because people don’t realize that dopamine means cocaine,” he says.

Smiling, Dr. Meck produces half of a journal article—the other half is still stuck in his printer, which is making nasty sounds—by Baylor College of Medicine researchers who found that different pathways were activated when people drank labeled versus unlabeled soft drinks. This method, he says, is a more “mature” way to get to the root of romantic love.

“Say we both fall in love with different women and suppose that they are equal. One is Pepsi and one is Coke. When they are anonymous, they activate one set of pathways, but when people know what they are they activate another pathway involved in brand loyalty,” says Dr. Meck. “Over time there is bonding; it’s an evolutionary thing. Two equally good reinforcers, but because of the advertising or the girl’s make-up you begin to convince yourself that it’s romantic love. Marriage is brand loyalty.”

As any jealous lover can tell you, fear of losing one’s partner plays a powerful role in inducing long-term bonding, and the findings of modern neuroscience have produced some evidence to support this anecdotal old-saw. “People who study emotions talk about loss, and the amygdala gets activated with fear or danger. It is easy to imagine this is a way of producing long term bonding, this fear,” Dr. Meck says.

And still, no matter how much evidence is amassed supporting the position—which is now widely accepted in scientific circles—that all brain processes have non-supernatural explanations, the vast majority of citizens resist this biological position. “It’s this idea that biological things are ‘dirty,’ that it’s wrong or dirty to feel lust for lots of people,” says Dr. Meck. “Humans are not monogamous. We force them to be. We can override nature with laws, we can punish them. Humans have this funny additional thing—introspection, conscience and the ability to plan into the future; they become burdens and we feel guilty.”

Sacrificing a glorified notion of love, in fact, may actively go against some of our innate tendencies. “It all has to be based on biology,” Dr. Meck says, “and our need to deny biology has biological basis. The cortex plans into the future and considers future consequences. It is saying there is some bigger picture.” This is one of the most interesting findings of neuroscience: that within the human brain there is a propensity to deny some “unpleasant” aspects of objective reality. And in some sad sense, the existence of this sort of cognitive machinery is not surprising. The process of natural selection that generated human beings only “sees” reproductive output. In effect, nature doesn’t care how you get the job done (produce a lot of offspring) just so long as you do. Having a piece of brain architecture that keeps you from believing that you are a gene-propagating automaton makes you more likely to remain nature’s slave.

Yet Dr. Meck resists the position that romantic love is a myth. “It’s not a myth: we created it. You create what you need. There is a constant interplay between biology and culture. You do what works for you. When you seek out a mate you tend to find someone with an equal level of stimulation seeking. You end up finding someone who matches this biological profile. That is what you’re seeking when you’re looking for a soul-mate.”

Considering that love is known to provoke appetite loss, depression, sleeplessness, anxiety, jealousy, fear, one might wonder if it is a disease. At the Student Health Center, Dr. Bill Purdy, assistant clinical professor of Student Health, takes a break from undergraduate gland palpation and tackles this question. As our resident healer, he sees more of the fallout from relationships—and condoms—gone bad than anyone. But he’s coy about romantic love being pathological.

“I don’t think romantic love is an illness,” he says, “but if it were, one would like it to be longterm, contagious, and incurable.”