Why We Love (8 page)

Take dopamine. Elevated levels of dopamine in the brain produce extremely focussed attention,
2
as well as unwavering motivation and goal-directed behaviors.
3
These are central characteristics of romantic love. Lovers intensely focus on the beloved, often to the exclusion of all around them. Indeed, they concentrate so relentlessly on the positive qualities of the adored one that they easily overlook his or her negative traits;
4
they even dote on specific events and objects shared with this sweetheart.

Besotted lovers also regard the beloved as novel and unique. And dopamine has been associated with learning about novel stimuli.
5

Central to romantic love is the lover’s
preference
for the beloved. As you recall from chapter two, among prairie voles, this favoritism is associated with heightened levels of dopamine in specific brain regions. And it is not a leap of logic to suggest that if dopamine is associated with mate preference in prairie voles, it can play a role in partiality in people. As you recall, all mammals have basically the same brain machinery, although size, shape, and placement of brain parts definitely vary.
6

Ecstasy is another outstanding trait of lovers. This, too, appears to be associated with dopamine. Elevated concentrations of dopamine in the brain produce exhilaration, as well as many of the other feelings that lovers report—including increased energy, hyperactivity, sleeplessness, loss of appetite, trembling, a pounding heart, accelerated breathing, and sometimes mania, anxiety, or fear.
7

Dopamine involvement may even explain why love-stricken men and women become so dependent on their romantic relationship and why they crave emotional union with their beloved. Dependency and craving are symptoms of addiction—and all of the major addictions are associated with elevated levels of dopamine.
8
Is romantic love an addiction? Yes; I think it is—a blissful dependency when one’s love is returned, a painful, sorrowful, and often destructive craving when one’s love is spurned.

In fact, dopamine may fuel the frantic effort a lover musters when he/she feels the love affair is in jeopardy. When a reward is delayed, dopamine-producing cells in the brain
increase
their work, pumping out more of this natural stimulant to energize the brain, focus attention, and drive the pursuer to strive even harder to acquire a reward: in this case, winning one’s sweetheart.
9
Dopamine, thy name is persistence.

Even the craving for sex with the beloved may be indirectly related to elevated levels of dopamine. As dopamine increases in the brain, it often drives up levels of testosterone, the hormone of sexual desire.

Norepinephrine’s High

Norepinephrine, a chemical derived from dopamine, may also contribute to the lover’s high. The effects of norepinephrine are varied, depending on the part of the brain it activates. Nevertheless, increasing levels of this stimulant generally produce exhilaration, excessive energy, sleeplessness, and loss of appetite—some of the basic characteristics of romantic love.

Increasing levels of norepinephrine could also help explain why the lover can remember the smallest details of the beloved’s actions and cherished moments spent together. This liquor is associated with increased memory for new stimuli.
10

A third chemical may also be involved in that “irresistible” feeling of magic Homer spoke of: serotonin.

Serotonin

A striking symptom of romantic love is incessant thinking about the beloved. Lovers cannot turn off their racing thoughts. Indeed, this single aspect of being in love is so intense that I use it as the litmus test of romantic passion. The first thing I ask anyone who tells me they are “in love” is, “What percentage of your waking hours do you think about your sweetheart?” Many say “over 90 percent.” Some bashfully admit they never stop thinking about “him” or “her.”

Lovers are obsessed. And doctors who treat individuals with most forms of obsessive-compulsive disorder prescribe SSRIs (selective serotonin reuptake inhibitors) such as Prozac or Zoloft, substances that
elevate
levels of serotonin in the brain.
11
So I came to suspect that the lover’s persistent, involuntary, irresistible ruminations about a sweetheart might be associated with
low
levels of some type (there are at least fourteen variations) of this chemical compound.
12

There is some support for my reasoning. In 1999, scientists in Italy studied sixty individuals: twenty were men and women who had fallen in love in the previous six months; twenty others suffered from unmedicated obsessive-compulsive disorder (OCD); twenty more were normal, healthy individuals who were not in love and were used as controls. Both the in-love participants and those suffering from OCD were found to have significantly lower levels of serotonin than did the controls.
13

These scientists examined serotonin levels in components of the blood, however, rather than the brain. Until scientists document the activity of serotonin in specific brain regions, we cannot be sure of the role of serotonin in romantic love. Nevertheless, this experiment has established, for the first time, a possible connection between romantic love and
low
levels of bodily serotonin.

All those countless hours when your mind races like a mouse upon a treadmill may be associated with reduced levels of serotonin coursing through the highways of the brain.

And as a love affair intensifies, this irresistible, obsessive thinking can increase—due to a negative relationship between serotonin and its relatives, dopamine and norepinephrine. As levels of dopamine and norepinephrine climb, they can cause serotonin levels to plummet.
14
This could explain why a lover’s increasing romantic ecstasy actually intensifies the compulsion to daydream, fantasize, muse, ponder, obsess about a romantic partner.

A “Working” Hypothesis

Given the properties of these three related chemicals in the brain—dopamine, norepinephrine, and serotonin—I began to suspect that all played a role in human romantic passion.

The feelings of euphoria, sleeplessness, and loss of appetite, as well as the lover’s intense energy, focussed attention, driving motivation, and goal-oriented behaviors, his/her tendency to regard the beloved as novel and unique, and the lover’s increased passion in the face of adversity might all be caused, in part, by heightened levels of dopamine and/or norepinephrine in the brain. And the lover’s obsessive cogitation about the beloved might be due to decreased brain levels of some type of serotonin.

Now for the caveats. This theory is complicated by many facts: different doses of these chemicals can produce different effects. These substances do different things in different brain parts. Each interacts with the others in different ways under different circumstances. And each harmonizes with many other bodily systems and brain circuits, setting up complex chain reactions. Moreover, passionate romantic love takes a variety of graded forms, from pure elation when one’s love is reciprocated to feelings of emptiness, despair, and often rage when one’s love is thwarted. These chemicals undoubtedly vary in their concentrations and combinations as the relationship ebbs and flows.

Nevertheless, the distinct correlation between numerous characteristics of romantic love and the effects of these three brain substances led me to the following hypothesis:
this fire in the mind is caused by elevated levels of either dopamine or norepinephrine or both, as well as decreased levels of serotonin.
These chemicals form the backbone of obsessive, passionate, romantic love.

Scanning the Brain in Love

Next, I needed to find the regions of the brain involved in Homer’s “pulsing rush of Longing.” I knew that dopamine, norepinephrine, and serotonin were much more prevalent in some brain regions than in others. If I could establish which regions of the brain become active while one is feeling romantic rapture, that might confirm which primary chemicals were involved. It was time to embark on the project to scan the brains of love-struck men and women.

With neuroscientist Greg Simpson, then at the Albert Einstein College of Medicine, I developed a scheme. We would collect data on brain activity while love-smitten subjects performed two separate tasks: looking at a photograph of his or her beloved, and looking at a “neutral” photograph of an acquaintance who generated no positive or negative romantic feelings. Moreover, we would use a functional magnetic resonance imaging (fMRI) machine to take pictures of the brain.

The fMRI machine records blood flow in the brain. It is based, in part, on a simple principle: brain cells that are active suck up more blood than quiescent brain parts—in order to collect the oxygen they need to do their job. Using this machine I would not need to inject my subjects with colored dye or intrude on their bodies in any other way. No pain. That appealed to me. Then to analyze our data, we would compare the brain activity that occurred while our subjects gazed at a photo of their sweetheart with their brain activity as they looked at the neutral image.

A good beginning, we thought. In 1996 we scanned four subjects, two young men and two young women. All were madly in love. The results were encouraging. But my colleague had to withdraw from the experiment due to other professional commitments. Fortunately I had already invited Lucy Brown, an accomplished neuroscientist at the Albert Einstein College of Medicine, to interpret the scanning results—a technologically sophisticated, time-gobbling, and intellectually demanding task. With time we were joined by Art Aron, a talented research psychologist at the State University of New York in Stony Brook, and the gifted Deb Mashek, then a graduate student in the SUNY Stony Brook psychology department.

I had one concern about the design of the experiment. As you recall, lovers have a hard time
not
thinking about their beloved. I was afraid that the lover’s passionate romantic thoughts, generated as he/she looked at the photo of a sweetheart, would carry over and contaminate their passive thoughts as they looked at the neutral photo. When I discussed this with Art and Deb, Art recommended a “distraction task,” a standard psychological procedure used to wash the brain clean of emotion. We settled on a particular “distraction task” that amuses me to this day.

Between looking at the positive photo of the sweetheart and the neutral photo of some boring acquaintance, subjects would be shown a large number (like 8,421) on the screen and be required to mentally count backward from this number in increments of seven. The point: to cleanse the mind of strong feelings between exposure to the beloved and exposure to the neutral stimulus. Try it the next time you are upset, very upset. Pick any large number; then really concentrate on counting backward in increments of seven starting with that number. It’s demanding. But it works. At least briefly, feelings simply fade away as you struggle to count accurately.

Before we started to scan more brains of love-stricken men and women, however, we had to be certain of one thing: that a photograph of the beloved would actually stimulate feelings of romantic love more effectively than would a smell, song, love letter, memory, or other object or phenomenon associated with the beloved.

Poets and artists have always known the power of visual images, of course. As William Butler Yeats wrote, “Wine comes in at the mouth / and love comes in at the eye.”
15
Most psychologists also assume that the visual image triggers romantic passion. We were convinced of this ourselves. But before we attempted to generate feelings of romantic ecstasy with a photograph, Art, Deb, and I wanted to be positive that love “comes in at the eye” more intensely than through some other sense.

To find out, we launched an ingenious experiment with a device we came to call the love-o-meter.

The Love-o-meter

On a bulletin board for psychology students on the SUNY Stony Brook campus, Art and Deb solicited men and women who were in love. The announcement began with bold letters: “Have you just fallen madly in love?” “Just” and “madly” were the operative words. We sought only candidates who were so intensely in love that they could hardly eat or sleep.

Lots of volunteers contacted Deb at the Stony Brook psychology department, then arrived in person. She selected those who seemed genuinely in love, and gave each several questionnaires designed to provide insights into their personality, their feelings about the beloved, and the duration, intensity, and status of their love affair. Then she asked each to return to the lab a week later, bearing items that made them feel intense romantic passion for their adored one. Back these students came with photographs, letters, e-mails, birthday cards, music tapes, colognes, memories written on sheets of paper, and notes about anticipated future events. They carried them like glass flowers.

Then each subject was prepared for the experiment. First Deb glued three electrodes to different regions of the scalp, thereby connecting the participant to an electroencephalograph (EEG). She told each subject that these wires would record their brain waves during the experiment. Actually, this wasn’t true; the machine was not turned on. But we hoped this deception would stimulate each volunteer to be honest. Then, the participant sat in front of a computer screen displaying an icon that looked like a vertically standing thermometer and was given a handheld rotating dial, arching from zero to thirty degrees. By turning this spring-loaded dial, the subject could raise the “mercury” in the thermometer. When he/she released the dial, it returned to zero. We jokingly called this computer-based response device our love-o-meter.

The experiment began. First the subject was shown the photograph of his/her beloved, then a neutral photo of someone else of the same sex or a photograph of nature. Second, each participant read a love letter from the beloved, then a paragraph from a statistics book. Third, each smelled a scent that reminded them of the beloved, then water with weak rubbing alcohol. Fourth, the subject was asked to “think back” to a wonderful moment with the sweetheart, then recall some mundane event such as the last time they washed their hair. Fifth, each heard a song they associated with their sweetheart, then a song sung by characters on the American children’s television show
Sesame Street.
Last, each participant was asked to imagine an exhilarating future event with the beloved, then a mundane incident such as brushing teeth. And each assignment was interspersed with our distraction task: mentally counting backward in increments of seven, starting with one from a sequence of large numbers.