Pair Bonding 101: Beware Novelty-As-Aphrodisiac

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How will you fill your pair-bonder “hole?”

Prairie volesIn recent years, scientists have been studying a fascinating mammal in greater depth: the prairie vole. There are many closely related vole species, but some species mate for life while others don't form pair bonds at all (like most mammals).

The prairie vole belongs to that curious 3 percent of "socially monogamous" mammal species, which includes humans. They pair up, usually for their short lives, sometimes with a bit of extra-pair coupling on the side ("cheating"). Again, like humans.

Evidence so far suggests that the brain mechanism that causes prairie voles to pair bond (i.e., an exaptation of the caregiver-infant bonding mechanism) probably has a lot in common with the brain mechanisms that cause us to pair bond. This makes these critters of special interest to humans:

Given the substantial overlap between mechanisms involved in formation of social bonds and addiction, the prairie vole appears to be a useful model for examining ... biological mechanisms. [From recent study]

Here are three intriguing prairie-vole findings, with implications for how we manage our love lives:

1.     Get a prairie vole high on amphetamines, which release a lot of dopamine into his brain, and he can't pair bond. The part of his brain that urges him to bond runs on the "gotta get it" neurotransmitter, dopamine. But, paradoxically, too much dopamine also starts to activate the dopamine receptors responsible for the aversion feelings that normally cause him to dislike "other" females. When overstimulated he doesn't bond with any females, though presumably he still likes sex thanks to his underlying mammalian "get it on" programming. Take-away message? Overstimulation of the reward circuitry can interfere with love.

2.     Next, offer amphetamines to both promiscuous and pair-bonding virgin voles. Prairie (pair-bonding) voles will use more. In short, the same reward circuitry in their brains that makes them want to fall head over heels also leaves them especially vulnerable to addiction. In contrast, most rodents don't like alcohol. They have to be bred specially to use it. But both prairie voles and humans will drink, suggesting that similarities in their reward circuitry make possible a strong buzz. In fact, scientists are now using prairie voles to screen medications for the treatment of alcoholism and addictions in recognition of their similarity to humans.

3.     Now, offer amphetamines to both prairie voles that have bonded with mates and those who haven't mated yet. The bonded ones don't find amphetamines appealing, but those without mates use the drug with gusto. Intense stimulation "hijacks" the brain mechanism that evolved to encourage pair bonding. Bottom line: Drugs can hijack the bonding mechanism, and register as a sort of love-substitute.

It's almost as if the reward circuitry of a pair bonder has a "little hole" crying out to be filled by a pair bond (even if the individual never bonds). In the absence of a mate, a pair bonder will look around for something else to fill that "hole." Obviously, we humans often try to fill the "hole" with lots of friends, serial affairs, porn, drugs, alcohol, devotion to a guru or a cause, or whatever—all of which furnish, or at least promise, some neurochemical satisfaction.

The important point is that the brain mechanism that primes a pair bonder to bond is mechanical, not rational. It drives behavior according to dopamine released. The more intense the stimulation, the more value we perceive in a given activity. How could something that excites such anticipation be the wrong choice? As anthropologist Helen Fisher says, "Love is not an emotion; it is a drive."

Throughout vole evolution, this yearning-for-dopamine orchestrated vole love lives fairly well. There were no evil scientists around purveying amphetamines. The voles didn't have to contend with synthetically jacked-up dopamine that derailed their delicate pair-bonding mechanism. Potential mates turned them on (got their dopamine soaring). They fell in vole love; mated like mad; and then settled down to raise the pups together.

Note: Pair bonding is not a moral strategy; it is a mating strategy, and arises from a subconscious brain mechanism. The vole example demonstrates that bonding is not a cultural phenomenon. Most pair bonders seem to have evolved this mating strategy because their offspring do better with two caregivers. Humans, for example, take a long time to mature, so parents who bond long enough to bond with us are good insurance.

Pair bonding is normally intrinsically rewarding

What maintains a pair bond? Not fervent sex (although it can initially help bond pairs because the brain wires itself to remember such a "valuable" experience). According to biologist David Barash, normal pair bonder "sexual behavior is neither especially frequent nor especially fervent." Many interactions between mates take the form of resting together, mutual grooming, and "hanging out." That said, regular flirty behavior and copulation certainly can be bonding behaviors.

The fact that pair bonders stay bonded without constant sexual fireworks suggests that the bond itself is normally rewarding. The fact that Mr. and Mrs. Vole turn up their noses at amphetamines underscores their contentment. Snuggling up in the corner of their cage feels better than getting high. Pair-bonder brains are set up to relish bonding for its own sake—unless something interferes. Companionship fills the little "hole," and many mates pass their lives in sexual monogamy.

That said, if a particularly enticing genetic opportunity knocks on the door, both male and female prairie voles have been known to philander—and then chase off the sexy intruder. After all, evolution really doesn't like monogamy much. It tolerates it grudgingly in relatively few species.

The point is that our pair-bonder genes have shaped our reward circuitry to value pair bonds and the odd extra-pair coupling. Caring for our little gene-packets in pairs, while mixing in some genetic variety on the side, offers the best of both worlds...from our genes' perspective.

Precisely why do we pair bonders cheat? Because dopamine soars between our ears. Period. Otherwise, we wouldn't. Trysts are risky because pair bonders innately engage in mate-guarding, and punish infidelity. Each partner's committed investment seems somewhat dependent upon the assumption that all resources are going to their joint offspring. "Deal's a deal."

Philandering pair bonders, then, take the leap for the same reason Hugh Grant and Elizabeth Hurley each did. Risk and novelty increase dopamine, making the opportunity seem worth the possible repercussions—at least in the moment. Morality might stop some humans from acting, but the urge to cheat arises from dopamine spurts in the brain. Novelty works as an aphrodisiac because of the same spurts.

What can humans learn from the way pair-bonding machinery works?

1.     A pair bond can be a source of powerful contentment. More and more research on humans (and other animals) confirms that affectionate touch and close, trusted companionship decrease stress, ease depression, speed healing, and help ward off addiction.

2.     Pair-bonding species rely heavily on companionship, flirty behavior, copulation and affectionate touch to stay bonded after an initial mating frenzy. Not on novelty.

Sexual variety3.     Too much competing stimulation (such as novelty) can hijack the delicate machinery on which our unions rest. When we are jolted with the extra dopamine of a possible affair, recreational drugs, cam-2-cam encounters and so forth, it can make our less stimulating primary bond look humdrum.

4.     Willing mates begging for action naturally tend to jack-up dopamine, as Tiger Woods discovered. But so do virtual "mates" moaning for attention. This is why today's Internet erotic possibilities have the potential to make us undervalue our pair bonds. (Sex toys can have the same effect, of course.)

Remember, the primitive part of the brain assesses sexual opportunities not on logic or inherent value, but solely on quantity of dopamine released in the moment.

Beware novelty-as-aphrodisiac

All of this means that much of today's sex advice won't work well for lovers who want to remain paired. It's based on the dopamine-cranking "novelty-as-aphrodisiac" strategy: trying a new sex toy, watching porn, swapping partners, acting out a kinky fantasy, engaging in daring or painful sex, and so forth. Novelty and fear are certainly arousing. Yet novelty-as-aphrodisiac has drawbacks.

First, once you've tried something, it's not novel anymore. To get the same thrill from it in the future, you may have to ratchet up the stimulation. That is, novelty-as-aphrodisiac is not sustainable. After you've pounded your brain with the excess dopamine produced by the obvious options, what do you do?

Second, too much stimulation can actually numb the brain's pleasure response. So, instead of feeling more contented or more bonded, lovers may feel more dissatisfied than ever in between intense, novelty-induced climaxes. Until you return your brains to normal sensitivity, you may look even duller to each other.

Suggestion: If you wish to sustain your pair bond as a source of contentment, first take a lesson from prairie voles: Do what you can to avoid the overstimulation that impairs bonding. This advice may be especially critical today because tempting novel mates are far more prevalent than they were as our brains evolved. (A kid in high school sees more hotties in the hall between classes than his ancestors saw in a lifetime, not to mention virtual hotties.)

Second, master and employ the attachment cues on which other pair-bonding species instinctively rely. Apparently, we humans also used to know them:

Those people are happy who relish love's pleasure

Enjoying Aphrodite's sensual embrace

As a ship riding easy on a calm sea,

Avoiding the obsession that leads to disgrace.

For sex, like a horsefly, can madden with its sting,

And Eros has two arrows to his string. . . .

A mere scratch from the first brings lifelong joy,

But the second wounds to death, and breeds despair.

—Euripides (ca. 480-406 BCE), Iphegenia at Aulis


Studies on the overlap between sex and drugs in the brain