The Molecule of More: How a Single Chemical in Your Brain Drives Love, Sex, and Creativity—and Will Determine the Fate of the Human Race

Human research in all its forms is tricky. It’s not the same as clinical care, in which a doctor and a patient work together to treat the patient’s illness. In that case, they choose whatever treatment they think will work best, and the only goal is to make the patient better.

The goal of research, on the other hand, is to answer a scientific question. Even though scientists work hard to minimize the risks to their participants, the science must come first. Sometimes, access to experimental treatments can be lifesaving, but usually research participants are exposed to risks they wouldn’t experience in the course of regular clinical care.

By volunteering to take part in studies, participants sacrifice some of their own safety for the benefit of others—sick people who will enjoy a better life if the research is successful. It’s like a firefighter running into a burning building to rescue the people trapped inside, choosing to place himself in danger for the welfare of others.

The key element, of course, is that the research participant needs to know exactly what she’s getting herself into. It’s called informed consent, and usually comes in the form of a lengthy document that explains the purpose of the research and lists the risks of becoming involved. It’s a good system, though not perfect. Participants don’t always read it carefully, especially if it’s very long. Sometimes researchers leave things out because deception is an essential part of the study. But, in general, scientists do their best to make sure their participants are willing partners as they tackle the mysteries of human behavior.

Love is a need, a craving, a drive to seek life’s greatest prize.

—Helen Fisher, biological anthropologist

Chapter 1

LOVE

You’ve found the one you waited for all your life, so why doesn’t the honeymoon last forever?

In which we explore the chemicals that make you want sex and fall in love—and why, sooner or later, everything changes.

Shawn wiped a clear space on his steamed-over bathroom mirror, ran his fingers through his black hair, smiled. “This’ll work,” he said.

He dropped his towel and admired his flat belly. His obsession with the gym had produced two-thirds of a six-pack. From that, his mind went to a more pressing obsession: he had not been out with anyone since February. Which was a nice way of saying he hadn’t had sex in seven months and three days—and he was disturbed to realize he had kept track so precisely. That streak ends tonight, he thought.

At the bar, he surveyed the possibilities. There were a lot of attractive women here tonight—not that looks were everything. He missed sex, sure, but he also missed having someone in his life, someone to text for no reason, someone who could be a welcome part of every day. He considered himself a romantic, even if tonight was just about sex.

He kept meeting the eyes of a young woman standing with a chatty friend at a high-top table. She had dark hair and brown eyes, and he noticed her because she wasn’t in the usual Saturday-night uniform; she had on flats instead of heels, and she wore Levis instead of club clothes. He introduced himself and the conversation came quickly and easily. Her name was Samantha, and the first thing she said was that she was more comfortable doing cardio than putting back beers. That led to an in-depth discussion of local gyms, fitness apps, and the relative merits of working out in the morning versus the afternoon. For the rest of the night he didn’t leave her side, and she quickly came to like having him there.

Lots of factors pushed them along to what would become a long-term relationship: their common interests, the ease they felt with each other, even the drinks and a little desperation. But none of that was the real key to love. The big factor was this: they were both under the influence of a mind-altering chemical. So was everyone else in the bar.

And, it turns out, so are you.

WHAT IS MORE POWERFUL THAN PLEASURE?

Dopamine was discovered in the brain in 1957 by Kathleen Montagu, a researcher working in a laboratory at the Runwell Hospital near London. Initially, dopamine was seen simply as a way for the body to produce a chemical called norepinephrine, which is what adrenaline is called when it is found in the brain. But then scientists began to observe strange things. Only 0.0005 percent of brain cells produce dopamine—one in two million—yet these cells appeared to exert an outsized influence on behavior. Research participants experienced feelings of pleasure when they turned dopamine on, and went to great lengths to trigger the activation of these rare cells. In fact, under the right circumstances, pursuit of feel-good dopamine activation became impossible to resist. Some scientists christened dopamine the pleasure molecule, and the pathway that dopamine-producing cells take through the brain was named the reward circuit.

The reputation of dopamine as the pleasure molecule was further cemented through experiments with drug addicts. The researchers injected them with a combination of cocaine and radioactive sugar, which allowed the scientists to figure out which parts of their brains were burning the most calories. As the intravenous cocaine took effect, participants were asked to rate how high they felt. Researchers discovered that the greater the activity in the dopamine reward pathway, the greater the high. As the body cleared the cocaine from the brain, dopamine activity decreased, and the high faded. Additional studies produced similar results. The role of dopamine as the pleasure molecule was established.

Other researchers tried to duplicate the results, and that’s when unexpected things began to happen. They reasoned that it’s unlikely that dopamine pathways evolved to encourage people to get high on drugs. Drugs were probably causing an artificial form of dopamine stimulation. It seemed more likely that the evolutionary processes that harnessed dopamine were driven by the need to motivate survival and reproductive activity. So they replaced cocaine with food, expecting to see the same effect. What they found surprised everyone. It was the beginning of the end for dopamine as the pleasure molecule.

Dopamine, they discovered, isn’t about pleasure at all. Dopamine delivers a feeling much more influential. Understanding dopamine turns out to be the key to explaining and even predicting behavior across a spectacular range of human endeavors: creating art, literature, and music; seeking success; discovering new worlds and new laws of nature; thinking about God—and falling in love.

Shawn knew he was in love. His insecurities melted away. Every day made him feel on the brink of a golden future. As he spent more time with Samantha, his excitement about her grew, and his sense of anticipation became constant. Every thought of her suggested limitless possibilities. As for sex, his libido was stronger than ever, but only for her. Other women ceased to exist. Even better, when he tried to confess all this happiness to Samantha, she interrupted him to say she felt exactly the same.

Shawn wanted to be sure they would be together forever, so one day he proposed to her. She said yes.

A few months after their honeymoon, things began to change. At the start they had been obsessed with one another, but, with the passage of time, that desperate longing became less desperate. The belief that anything was possible became less certain, less obsessive, less at the center of everything. Their elation receded. They weren’t unhappy, but the profound satisfaction from their earlier time together was slipping away. The sense of limitless possibilities began to seem unrealistic. Thoughts about each other, that used to come constantly, didn’t. Other women began to draw Shawn’s attention, not that he intended to cheat. Samantha let herself flirt sometimes, too, even if it was no more than a shared smile with the college boy bagging groceries in the checkout line.

They were happy together, but the early gloss of their new life began to feel like their old life apart. The magic, whatever it was, was fading.

Just like my last relationship, thought Samantha.

Been there, done that, thought Shawn.

MONKEYS AND RATS AND WHY LOVE FADES

In some ways rats are easier to study than human beings. Scientists can do a lot more to them without having to worry about the research ethics board knocking at their door. To test the hypothesis that both food and drugs stimulate dopamine, the scientists implanted electrodes directly into rats’ brains so they could directly measure the activity of individual dopamine neurons. Next, they built cages with chutes for food pellets. The results were just as they expected. As soon as they dropped the first pellet, the rats’ dopamine systems lit up. Success! Natural rewards stimulate dopamine activity just as well as cocaine and other drugs.

Next they did something the original experimenters had not. They kept going, monitoring the rats’ brains as pellets of food were dropped down the chute, day after day. The results were wholly unexpected. The rats devoured the food as enthusiastically as ever. They were obviously enjoying it. But their dopamine activity shut down. Why would dopamine stop firing when stimulation keeps coming? The answer came from an unlikely source: a monkey and a light bulb.

Wolfram Schultz is among the most influential pioneers of dopamine experimentation. As a professor of neurophysiology at the University of Fribourg, Switzerland, he became interested in the role of dopamine in learning. He implanted tiny electrodes into the brains of macaque monkeys where dopamine cells clustered together. He then placed the monkeys in an apparatus that had two lights and two boxes. Every once in a while one of the lights turned on. One light was a signal that the food pellet could be found in the box on the right. The other meant the food pellet was in the box on the left.

It took the monkeys some time to figure out the rule. At first they opened the boxes randomly, and got it right about half the time. When they found a food pellet, the dopamine cells in their brain fired, just as in the rats. After a while, the monkeys figured out the signals and reached for the correct, food-containing box every time—and at that, the timing of the dopamine release began to change from firing at the discovery of the food to firing at the light. Why?

Seeing the light go on would always be unexpected. But once the monkeys figured out that the light meant they were about to get food, the “surprise” they felt came exclusively from the appearance of the light, not from the food. From that, a new hypothesis arose: dopamine activity is not a marker of pleasure. It is a reaction to the unexpected—to possibility and anticipation.

As human beings, we get a dopamine rush from similar, promising surprises: the arrival of a sweet note from your lover (What will it say?), an email message from a friend you haven’t seen in years (What’s the news going to be?), or, if you’re looking for romance, meeting a fascinating new partner at a sticky table in the same old bar (What might happen?). But when these things become regular events, their novelty fades, and so does the dopamine rush—and a sweeter note or a longer email or a better table won’t bring it back.

This simple idea provides a chemical explanation for an age-old question: Why does love fade? Our brains are programmed to crave the unexpected and thus to look to the future, where every exciting possibility begins. But when anything, including love, becomes familiar, that excitement slips away, and new things draw our attention.

The scientists who studied this phenomenon named the buzz we get from novelty reward prediction error, and it means just what the name says. We constantly make predictions about what’s coming next, from what time we can leave work, to how much money we expect to find when we check our balance at the ATM. When what happens is better than what we expect, it is literally an error in our forecast of the future: Maybe we get to leave work early, or we find a hundred dollars more in checking than we expected. That happy error is what launches dopamine into action. It’s not the extra time or the extra money themselves. It’s the thrill of the unexpected good news.

In fact, the mere possibility of a reward prediction error is enough for dopamine to swing into action. Imagine you’re walking to work on a familiar street, one you’ve traveled many times before. All of a sudden you notice that a new bakery has opened, one you’ve never seen. You immediately want to go in and see what they have. That’s dopamine taking charge, and it produces a feeling different from enjoying how something tastes, feels, or looks. It’s the pleasure of anticipation—the possibility of something unfamiliar and better. You’re excited about the bakery, yet you haven’t eaten any of their pastries, sampled any of their coffee, or even seen how it looks inside.

You go in and order a cup of dark roast and a croissant. You take a sip of the coffee. The complex flavors play across your tongue. It’s the best you’ve ever had. Next you take a bite of the croissant. It’s buttery and flaky, exactly like the one you had years ago at a café in Paris. Now how do you feel? Maybe that your life is a little better with this new way to start your day. From now on you’re going to come here every morning for breakfast, and have the best coffee and flakiest croissant in the city. You’ll tell your friends about it, probably more than they care to hear. You’ll buy a mug with the café’s name on it. You’ll even be more excited to start the day because, well, this awesome café, that’s why. That’s dopamine in action.

It’s as if you have fallen in love with the café.

Yet sometimes when we get the things we want, it’s not as pleasant as we expect. Dopaminergic excitement (that is, the thrill of anticipation) doesn’t last forever, because eventually the future becomes the present. The thrilling mystery of the unknown becomes the boring familiarity of the everyday, at which point dopamine’s job is done, and the letdown sets in. The coffee and croissants were so good, you made that bakery your regular breakfast stop. But after a few weeks, “the best coffee and croissant in the city” became the same old breakfast.

But it wasn’t the coffee and the croissant that changed; it was your expectation.

In the same way, Samantha and Shawn were obsessed with each other until their relationship became utterly familiar. When things become part of the daily routine, there is no more reward prediction error, and dopamine is no longer triggered to give you those feelings of excitement. Shawn and Samantha surprised each other in a sea of anonymous faces at a bar, then obsessed over each other until the imagined future of never-ending delight became the concrete experience of reality. Dopamine’s job—and ability—to idealize the unknown came to an end, so dopamine shut down.

Passion rises when we dream of a world of possibility, and fades when we are confronted by reality. When the god or goddess of love beckoning you to the boudoir becomes a sleepy spouse blowing his or her nose into a ratty Kleenex, the nature of love—the reason to stay—must change from dopaminergic dreams to . . . something else. But what?

ONE BRAIN, TWO WORLDS

John Douglas Pettigrew, emeritus professor of physiology at the University of Queensland, Australia, is a native of the delightfully named city of Wagga Wagga. Pettigrew had a brilliant career as a neuroscientist, and is best known for updating the flying primates theory, which established bats as our distant cousins. While working on this idea, Pettigrew became the first person to clarify how the brain creates a three-dimensional map of the world. That sounds far removed from passionate relationships, but it would turn out to be a key concept for explaining dopamine and love.

Pettigrew found that the brain manages the external world by dividing it into separate regions, the peripersonal and the extrapersonal—basically, near and far. Peripersonal space includes whatever is in arm’s reach; things you can control right now by using your hands. This is the world of what’s real, right now. Extrapersonal space refers to everything else—whatever you can’t touch unless you move beyond your arm’s reach, whether it’s three feet or three million miles away. This is the realm of possibility.

With those definitions in place, another fact follows, obvious but useful: since moving from one place to another takes time, any interaction in the extrapersonal space must occur in the future. Or, to put it another way, distance is linked to time. For instance, if you’re in the mood for a peach, but the closest one is sitting in a bin at the corner market, you can’t enjoy it now. You can only enjoy it in the future, after you go get it. Acquiring something out of your reach may also take some planning. It could be as simple as standing up to turn on a light, walking to the market for that peach, or figuring out how to launch a rocket to get to the moon. This is the defining characteristic of things in the extrapersonal space: to get them requires effort, time, and in many cases, planning. By contrast, anything in the peripersonal space can be experienced in the here and now. Those experiences are immediate. We touch, taste, hold, and squeeze; we feel happiness, sadness, anger, and joy.

This brings us to a clarifying fact of neurochemistry: the brain works one way in the peripersonal space and another way in the extrapersonal space. If you were designing the human mind, it makes sense that you would create a brain that distinguishes between things in this way, one system for what you have and another for what you don’t. For early humans, the familiar phrase “either you have it or you don’t” could be translated into “either you have it or you’re dead.”

From an evolutionary standpoint, food that you don’t have is critically different from food that you do have. It’s the same for water, shelter, and tools. The division is so fundamental that separate pathways and chemicals evolved in the brain to handle peripersonal and extrapersonal space. When you look down, you look into the peripersonal space, and for that the brain is controlled by a host of chemicals concerned with experience in the here and now. But when the brain is engaged with the extrapersonal space, one chemical exercises more control than all the others, the chemical associated with anticipation and possibility: dopamine. Things in the distance, things we don’t have yet, cannot be used or consumed, only desired. Dopamine has a very specific job: maximizing resources that will be available to us in the future; the pursuit of better things.

Every part of living is divided in this way: we have one way of dealing with what we want, and another way of dealing with what we have. Wanting a house, experiencing the kind of desire that motivates the hard work necessary to find it and purchase it, uses a different set of brain circuits than enjoying it once it’s yours. Anticipating a raise activates future-oriented dopamine, and it feels very different from the here-and-now experience of receiving the larger paycheck for the second or third time. And finding love takes a different set of skills than making love stay. Love must shift from an extrapersonal experience to a peripersonal one—from pursuit to possession; from something we anticipate to something we have to take care of. These are vastly different skills, which is why over time the nature of love has to change—and why, for so many people, love fades away at the end of the dopamine thrill we call romance.

Yet many people make the transition. How do they do it—how are they outsmarting the seduction of dopamine?

GLAMOUR

Glamour is a beautiful illusion—the word “glamour” originally meant a literal magic spell—that promises to transcend ordinary life and make the ideal real. It depends on a special combination of mystery and grace. Too much information breaks the spell.

—Virginia Postrel

Glamour is present when we see things that stimulate our dopaminergic imagination, drowning out our ability to accurately perceive here-and-now reality.

A good example is air travel. Look up. Is there an airplane in the sky? What kinds of thoughts and feelings are triggered? Many people experience a longing to be on the plane, traveling to exotic locations that are far away—a carefree getaway that begins with a ride among the clouds. Of course, if you were on the plane, your here-and-now senses would inform you that this paradise in the sky is more like a rush-hour bus across town: cramped, exhausting, and unpleasant—the opposite of elegant.

Likewise, what could be more glamorous than Hollywood? Beautiful actors and actresses go to parties, stand around swimming pools, and flirt. The reality is far different, involving 14-hour days sweating under hot lights. Women actors are exploited sexually and men are pressured to take steroids and growth hormone to get the fabulous bodies we see on screen. Gwyneth Paltrow, Megan Fox, Charlize Theron, and Marilyn Monroe have all described “casting couch” experiences (all but Marilyn Monroe said they declined the offer to trade sex for a coveted role). Nick Nolte, Charlie Sheen, Mickey Rourke, and Arnold Schwarzenegger have all admitted to using steroids, which can cause liver damage, mood swings, violent outbursts, and psychosis. It’s a tawdry business.

Mountains aren’t tawdry, though. They’re majestic, standing far off in the distance, softened by the blurring effect of miles of air, like a soft-focus photograph of a bride on her wedding day. Those with higher levels of dopamine want to climb it, explore it, conquer it. But they can’t, because it doesn’t exist. The mountain itself exists. But the imagined experience of being on it is impossible to achieve. The reality is that most of the time you’re on a mountain you can’t even tell. Typically you’re surrounded by trees, and that’s all you see. Occasionally you might come to a scenic overlook in which you can see for miles over the valley. But as you look, it’s the far-away valley that’s full of promise and beauty, not the mountain you’re standing on. Glamour creates desires that cannot be fulfilled because they are desires for things that exist only in the imagination.

Whether it’s an airplane in the sky, a movie star in Hollywood, or a distant mountain, only things that are out of reach can be glamorous; only things that are unreal. Glamour is a lie.

One day at lunch, Samantha ran into Demarco, her last serious boyfriend before Shawn. They hadn’t seen each other in years, hadn’t even come across each other on Facebook. She found him as funny and smart as ever, and in great shape, too. In minutes she was starry-eyed again. Here was something she hadn’t felt in a long time, the surge of excitement and the sense of possibility with a man who connected with her, someone who seemed full of fresh things for her to discover. He was excited, too, and anxious to share his feelings. The first thing he shared was how excited he was to be engaged. His fiancée was “the one” and he hoped Samantha would meet her, because he had never cared for someone so special as this new woman.

After Demarco left, Samantha decided this was a good day to drink. She adjourned to the bar and ordered a basket of tortilla chips and a Miller Lite, and spent the next half-hour picking at the label. She loved Shawn, she really did—or did she? They had been in a rut for most of a year. That feeling with Demarco was what she wanted. She had once had it with Shawn, but not anymore.

THE DARK SIDE

There’s a dark side to dopamine. If you drop a pellet of food into a rat’s cage, the animal will experience a dopamine surge. Who knew that the world was a place where food dropped from the sky? But if you keep dropping pellets every 5 minutes, dopamine stops. The rat knows when to expect the food, so there’s no surprise, and there is no error in the rat’s prediction of a reward. But what if you drop the pellet at random times, so it’s always a surprise? And what if, instead of rats and food pellets, you replace them with people and money?