The Science of Love

Love is difficult to describe. Poets and lyricists have tried doing so for eons. And they're still at it.

But how would a scientist describe love? It probably wouldn't be as romantic as a poet's or lyricist's description. I fancy it would be something like this:

Love is a chemical attraction between two people, influenced by environmental and cultural factors, for the purposes of finding a suitable mate to further one's family line.

Simple as that.

Helen Fisher, an anthropologist at Rutgers University and one of the most well-known researchers in the science of love, would go a bit further and define it in three sequential phases:

1. Lust
2. Attraction
3. Attachment

At each stage, there are identifiable patterns within a person's brain, hormonal balances, and neurotransmitters. Thus, love can be scientifically identified by examining the chemicals in your brain.

1. Lust

Chemically, the first reaction to another person is lust. This phase is driven by the sex hormones testosterone and estrogen, both of which occur in men & women and enhance a person's libido & carnal yearnings. These lead to a heightened sense of basic sexual drivers such as appearance and pheromones.

Appearance

No one wants to admit they're superficial, though we all care about our partner's looks to a certain extent. Through extensive research, evolutionary psychologist Devendra Singh of the University of Texas discovered that, on average, men tend to prefer women with a waist-to-hip ratio of 0.7. This applies to any weight category, culture, or ethnicity.

Psychology professor Robert Kurzban of the University of Pennsylvania also added a person's BMI (body mass index) and facial symmetry as factors in general attractiveness. Men typically look for BMI and facial features that hint at fertility, health, and youthfulness. Women typically look for BMI features that hint at virility, strength, health, and ability to provide (meaning social status indicators like salary and education).

Overall, men tend to favor visual stimulation while women tend to favor men with high social status. This helps to explain why the porn industry caters largely to men and why "gold diggers" are generally women.

All of this happens unconsciously, of course, within systems as primal as thirst and hunger. But you can see the evolutionary foundations for such factors. We're seeking out a mate that is capable of producing healthy offspring. How romantic.

Also gives new meaning to "love at first sight," huh?

Pheromones

Smell and pheromones have just as much of an impact too. Professor Claus Wedekind of the University of Bern in Switzerland found that women are consistently drawn to the smell of men whose immune systems are different from their own. The more different the immune system, the wider the range of immunities their offspring would have. This is known as disassortative sexual selection.

Then Dr. Martha McClintock of the University of Chicago made a related discovery. Her studies suggest that women are drawn to a man whose smell is most similar to her father. Electra complex, anyone?

These two smell preferences are not in conflict. A man with an immune system close to her father's would indicate a proven immune system (after all, it worked for Dad) while being different enough to provide complementary immunities. Both work hand-in-hand. (Or rather, nose-to-nose?)

The perfume industry is keenly aware of this; they routinely use pheromones to perfect their aromatic concoctions. It's like a match made in a perfume bottle.

Unfortunately, the phrase "love at first smell" isn't as catchy, is it?

2. Attraction

When most people talk about love, they're referring to this stage. This phase is driven by a suite of neurotransmitters called monoamines: norepinephrine, dopamine, and serotonin. They are responsible for those puppy-dog feelings. In fact, they're like a drug cocktail of lovey dovey motions and emotions.

Norepinephrine

This chemical influences the attention and reaction centers of the brain. In drastic situations, like being in love, it works alongside ephinephrine (the scientific name for adrenaline) to trigger the fight-or-flight response. No, this doesn't mean you'll run from your date or throw a punch. It means you'll feel an increased heart rate, blood flow, and energy levels. Also, your palms will get sweaty. Dawww.

Dopamine

This chemical triggers an intense rush of pleasure (aw yea), increased energy, focused attention, and decreased need for sleep or food. It also stimulates the reward center of the brain, reinforcing the need to continue seeing your love interest. Cocaine and nicotine trigger many of these feelings too, coincidentally, except it reinforces your need to continue using the drug—hence, addictions. Thus, if you were to look at the brain of a person in love, it would look just like an addict high on drugs. (I'm high on you, baby!)

Serotonin

This chemical inhibits aggression, appetite, sleep, mood, and most importantly for this situation, sexuality. So you'll be glad to hear that serotonin levels are dropped during this phase. What you may not be glad to hear is that low levels of serotonin are most closely associated with OCD (obsessive-compulsive disorder), though they can also indicate depression or anxiety. Serial killers also have low levels of serotonin (though being attracted to someone isn't going to make you a serial killer, I'm pretty sure). This explains why we're all a little nuts when we're in love; we're literally and chemically obsessing over our partner.

Physiology

Ph.D. student Andreas Bartels and his adviser Semir Zeki of the Imperial College of London used an fMRI (functional magnetic resonance imaging) scanner to scan brains in love. They discovered that the portions of the brain related reward and pleasure activate while portions related to moral judgment deactivate. A drop in moral judgment? This is apparently why people say that "love is blind". If you're in love, it doesn't matter what kind of scumbag your partner is; you're in love, and that's that.

3. Attachment

Long-term relationships and marriages wouldn't work without this stage. This phase is driven by the important hormones oxytocin and vasopressin. Whether you like it or not, our bodies physically deemphasize lust and attraction sooner or later. That's where these last two hormones come into play; they foster long-standing relationships and bonds that keep couples together as they have children and form families.

Oxytocin

This hormone is released during a wide range of relationship-building activities such as hugging, touching, orgasm, and child birth. Once released, the body experiences heightened sexual arousal, desire for bonding (which explains the cuddling after sex), maternal behavior, increased trust and reduced fear, and increased empathy & generosity.

One of the more famous studies of the effects of oxytocin is on prairie voles. Why prairie voles? Because only 3% of the mammals in this world form monogamous relationships, and prairie voles are one of them. Another would be humans, despite what you might see on Sex and The City.

Similar to humans, when prairie voles have sex, oxytocin and vasopressin is released. Scientists found that blocking these hormones would negate the voles' monogamy. Conversely, injecting a vole with these hormones and preventing it from having sex (sorry vole) would result in monogamy.

Assistant professor of psychology Diane Witt from New York also discovered oxytocin aids in child rearing. When blocking the release of oxytocin in rats, she found that they rejected their offspring. Conversely, injecting a female rat with oxytocin makes it nurture another female's young as if they were her own.

This doesn't mean human love can be had with a simple injection; human love is much more complex than that. But this does demonstrate the powerful relationship-building effects of oxytocin. The evolutionary need for it is fairly clear too. Without it, couples are less likely to stay together and raise healthy offspring.

In fact, it is generally believed that the more sex a couple has, the more likely they are to stay together. Does that mean the next time you ask for a quickie, you can say, "But baby, I'm doing it for us, for the relationship?" Heh heh…

Vasopressin

This hormone is generally used to regulate the body's retention of water, though it also has some neurological effects on the brain, all of which are not yet known. Like oxytocin, it is also released after orgasm. It also may aid in memory formation, tighten bonds between sexual partners, and in males, increase aggression against other males (perhaps against other suitors?).

Back to the prairie voles. When vasopressin was blocked in male prairie voles, they lost their devotion to their mates and did not protect them from new suitors. Research is still being done to discover the exact effects of vasopressin.

Chemical Romance, Chemical Love

So there you have it. Love broken down as a series of chemicals being released in three stages. Makes me wonder if this would make for a good Valentine's Day card:

When I first saw and smelled you,
testosterone and estrogen were released into my brain.
Then came norepinephrine, serotonin,
and enough dopamine to feel like I was high on cocaine.
Now that we're past those two stages,
it's mostly oxytocin and vasopressin going in my mind.
So baby won't you please,
oh won't you please be my Chemical Valentine?

Hmm. Probably not. Scientists and Hallmark don't mix.