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It’s one thing, a beautiful thing, to watch a falcon swoop off a 2,500-foot cliff. But to watch a man run to the edge and hurl his earthbound body into the void is to feel ill. Primates just aren’t supposed to do this. Don’t try telling that to , though. When the 28-year-old Aspenite started BASE-jumping a few years ago, he found his destiny.

“I always wanted to fly. I love anything involving big air,” says Davenport, who’s also a champion extreme skier.

On this winter morning in western Colorado, the wind is blowing steady at about 25 miles an hour, whipping my hair around my face. We’re at the top of an outcrop that Ted calls the “W Hotel,” because of the letter shape its gray gullies make against the cliff face. Davenport and six of his buddies are standing near the precipice, hands in pockets, shuffling their feet. The guys are nervous as calves at a branding, some of them more so than others.

These seven friends, most of whom live around Denver, do a lot of crazy stuff together. They go to Moab to jump into canyons and build big bonfires and shoot skeet. They dive off hotels in Denver and try to shake the police. But it’s not so much their jumps that I’m here to watch; it’s their brains. What makes one person fling himself off a cliff with abandon and another stay home to watch the Food Network? Even among rad adventurers, why do some hesitate when things get extreme? During the past half-decade—and especially the past year—scientists have been using high-tech imaging, advanced neurochemistry, and even computer games to tease out an answer to that question. They are opening a window on one of humanity’s most mysterious traits: the way we hear the call of adventure.

Atop the cliff, Collin Scott, 34, tries to light a wind indicator, a rolled-up piece of paper he’ll toss into the abyss. But Ted isn’t waiting for any indicators. “It’s windy as fuck,” he declares. Calling out to 24-year-old Matt Hecker, he says, “Get your gear on, pussy.” Ted wouldn’t say that to the others, but he knows Matt has both a similar level of experience and a similar worldview—one that often includes the surface of the earth approaching at near-terminal velocity.

Ted dons a helmet and parachute, then stuffs a walkie-talkie in one pants pocket and a bottle of water in the other. He grins for a picture, then asks me to send it to his family if it’s the last shot of him ever taken. He roars with laughter. Then he gets serious. He pauses for a second, walks briskly to the lip, and launches belly first into the air.

A few seconds later, his chute opens and he lands lightly on the rocky side of a ravine. The men up top cluster around their receiver. Ted’s voice comes in scratchy, as if he’s miles away. He’s all business. “I’m not going to lie,” he crackles. “There’s definitely turbulence pushing you around. Keep away from the wall. There’s no wind at all down here. Wooooyeah!”

Collin shakes his head. “I’ve made the decision,” he says. “I'm not going.” Collin is a software salesman, the only man here with a wedding ring. Peter Konrad, a 34-year-old pilot who until recently worked for a Denver telecom company, nods in agreement. He’s just three weeks past a car accident, the stitches on his forehead still red. Denver real estate investor Kevin Cochran is not jumping either. So there’s at least a little bit of sense in this crowd.

But then off the rest go. Next into the air is Jacob Fuerst, a 25-year-old former marine who after seven months in Iraq has found a measure of peace jumping off tall objects and taking photographs, often at the same time. Next Matt, without much ado, jumps into the void. Three years ago he spent 16 days in a coma after his paraglider seized up in north Boulder. It doesn’t seem to have slowed him down. Jeremy Puhal, 30, wants to jump, but he’s taking his time, waiting for a lull in the wind that never comes. Finally, he shakes out his cold arms, runs to the edge, and flies off.

Chances are, if you’re leaping into dead air from fixed objects, you’ve been pretty hairball your whole life. Ted estimates he’s been to the emergency room about 30 times, for everything from falling off a gymnastics horse when he was five to breaking his back on skis. Collin used to jump out of a backyard treehouse holding an umbrella. Last summer, Peter and two friends suspended a futon from the basket of a hot-air balloon. “We did tests on it to make sure it wouldn’t taco up on us,” he says, as if that somehow made it OK. They reclined on pillows 5,500 feet up in the heavens. Then they jumped out of bed.

Listening to Peter reminds me of . Remember him, the guy who tied 45 helium balloons to his Sears lounger in 1982 and shot up into LAX airspace with a few Miller Lites and a pellet gun? Even though Larry lived, he received an honorable mention from , which are given to “salute the improvement of the human genome by honoring those who accidentally remove themselves from it.”

The Darwin Awards are a clever idea, but scientists now know that doing reckless, stupid things is as much a part of our gene pool as red hair and a taste for peanut M&M’s. In fact, we may owe the continued existence of the human species to those crazy adventurers who weren’t content to squat around and eat bugs with a long stick—the ones genetically inclined to seek out the better-tasting protein, the greener pastures, the prettier mates from unfamiliar territory. “As our species evolved, communities with risk takers might have done better at things like warding off attackers,” says Thomas Crowley, a psychologist at the University of Colorado Denver. “Risk taking was important for the species and the individual.”

There was also, of course, something adaptive about staying in the grotto to doodle with chalk rather than fight the mastodon. And so, many of us have some ’fraidy-cat genes, too. Not surprisingly, some of these differences shake out by gender, but there are many and notable exceptions. Witness free climber Steph Davis, who frequently jumps off objects in a “squirrel suit” and last summer broke her pelvis jumping (with Ted) off our very same W Hotel.

As neuroscientists are discovering, there’s a little bit of Lawn Chair Larry in most of us. When we drop into a stream’s tongue or thread a mountain bike between rocks, all our senses buzz to life. The garage-band noise in our head fades away. When I ask Christopher Swain, a long-distance open-water swimmer who battles lightning storms and lamprey eels, to describe what happens when he’s in the zone, his answer is less about adrenaline than spirituality. But it’s still rooted in the cascade of natural opioids released from the brain. “I have trouble feeling where the river stops and my body starts,” he says. “I feel very calm. It’s a Zen state. I surrender.” Or, as kayaker Trip Jennings, who’s pioneered first descents on rivers all over the world, puts it, “I feel focus but also a sensation of freedom and intuition. I love that first stroke, when you’re fully committed.”

We all sit somewhere on the spectrum of “sensation seeking,” a term coined by University of Delaware psychologist Marvin Zuckerman. In the 1960s, Zuckerman noticed that the volunteers who came in for lab tests in sensory deprivation tended to be carrying motorcycle helmets. He began to wonder if there was a personality type that sought thrills, and so he developed the first-generation questionnaires to find out.

What Zuckerman and subsequent researchers discovered was that roughly 10 percent of us fall into the high-risk-taking end of a bell curve, with the Ted Davenports representing a small percentage of that. Thrill seekers tend to be open-minded, intelligent, and curious. They invent new sports, run for office, work on Wall Street, and perform high-stakes surgery. They’re also more likely to bust their skulls open or get hooked on crack.

That’s the thing: Just as it was evolutionarily adaptive for some individuals of the species to take extreme risks, so it was adaptive for them to get completely charged doing so. And those very qualities are now visible in the lab. Using a new generation of questionnaires and peering at the brain through radioactive imaging and functional magnetic resonance imaging (fMRI), neuroscientists can actually watch the brain’s risk-assessing centers in action.

So we decided to put half a dozen sensation seekers into the testing loop connecting them with a researcher who used personality questionnaires to see where they fell on the risk scale. What was going on in their gray matter, anyway? In Ted’s case, we decided to look inside and find out.

Ted’s city clothes are a combination of gangsta and woodsman. When I meet him at LAX a few weeks after the jump, he’s wearing low-slung jeans, a plaid shirt, and a black cap sprouting white tendrils of iPhone cord. He’s recently learned that a friend back home in Aspen, former ski patroller Cory Brettman, has died in an avalanche, and he’s texting his girlfriend, 27-year-old Amber Matthews, and his older brother, two-time world extreme-skiing champ Chris Davenport, to make sure everyone’s bearing up. Ted is also crushed to hear it’s dumping dumping! snow in Colorado. He’d much rather be there, skiing in a Warren Miller movie and training for the Freeride World Tour (he won the European tour in 2005) than on the expressway headed to UCLA’s brain-mapping center. Still, he’s sweet and cheerful and amped to donate his lobes to science.

But first, I figure he deserves a nice lunch in Westwood. Surrounded by suits at the Napa Valley Grille, Ted looks longingly at the wine list, but the university’s researchers have said he can’t drink. Instead, he consumes a Black Angus cheeseburger and tells me about the time he hit the wall literally in Magland, France.

It was February 2006, just before he was to compete in a European freeskiing event. He was BASE-jumping off a 1,300-foot cliff near Chamonix, and still a relative novice he uncorked his parachute too early and it twisted. Instead of pointing away from the wall, he slammed into it at 25 miles per hour, about 700 feet up. Ted attributes the accident to “pilot error.”

“It was like being on a swing set,” he says. “I hit with my feet and snapped my left foot completely in half, breaking all the metatarsal bones where the arch is.” Luckily, a headwind kept his chute inflated long enough for him to swerve away from the cliff, and when he landed in the weeds, he was laughing his head off. “I was so jacked with adrenaline,” he says. “I was so happy to be alive.” Even later, he was relatively unfazed. “Never for a single second did I consider not jumping again. I was like, I can’t wait to jump again.” His eyes open wide and he dives into his spiced-pear sorbet.

Like I said, Ted is a little different.

Half an hour later, we’re at UCLA’s Ahmanson-Lovelace Brain Mapping Center, one of the country’s top neuroimaging labs, talking to neuroscientist Russell Poldrack. In his early forties, wearing a leather jacket and geeky-chic black plastic glasses, Poldrack looks a lot more comfortable behind a computer terminal than he would, say, on a cyclo­cross course. His idea of risk is skipping the warranty when he buys an appliance.

Much of Poldrack’s work is geared toward understanding risky decision making in people, particularly drug abusers, but some of the same pathways are involved in the thirst for adventure. There are three major emotional ingredients to risk taking, he explains, all driven by individual brain chemistry. One is desire for adventure (“sensation seeking”), in what’s known as the reward pathway of the brain, the mysterious mechanisms where happiness juices flow; high-risk takers may simply get a bigger bang than other people, leading them to seek more intense experiences. Another is a relative disregard for harm, meaning, basically, that they’re not as afraid of negative consequences as regular folks. The third is impulsivity, or acting on your desires without fully thinking them through.

Ted? Check, check, check.

What distinguishes an everyday adventurer from an extreme or foolhardy one lies in the interplay of these factors. Mountaineers may be adventurous and well able to handle stress, but they tend not to be impulsive, often carefully planning their expeditions for months. I might equivocate before skiing a steep chute; you, on the other hand, might feel wiggy-out-of-your-mind ecstatic at the prospect. Will each of our experiences be worth it? This is known as the risk-reward calculus, and we make it all the time in our work, in our relationships, and in our sports.

In the reception area, Ted removes his iPhone and other metal objects. Without a hat or helmet on, he looks smaller, more fragile, but still humming with energy. He flashes us his pink-and-blue boxers, practices the computer game Poldrack has set up, and then steps into the room with the lab’s colossal white 3 Tesla Siemens MRI machine. He puts on virtual-reality prism glasses and headphones, waves cheerfully, and lies down. The bed slides into the tube like a morgue drawer.

The process of imaging with fMRI, which takes an almost continuous picture of the brain over time, is only about two decades old. While Ted plays a risk-tolerance-testing video game, the cylindrical machine takes a high-resolution picture every two seconds, highlighting the parts of Ted’s brain that are believed to be active and firing neurons. Later, Poldrack will slice the images like ham on a deli machine, pinpointing the action in 3-D. (Ted is fated for two more MRIs in the next three weeks one for a torn rotator cuff that he’ll get while skiing off a 30-foot jump, and another to check prior knee surgery, the result of crashing his snowmobile into a tree two years ago.)

To measure the risk-reward pathway, Poldrack uses a gambling game called BART, which stands for Balloon Analogue Risk Task. In his goggles, Ted sees a cartoon balloon on a computer screen. He presses a button to inflate the balloon, and as the balloon gets bigger, he “wins” more money, or, in this case, points. But the balloon will randomly pop, in which case he’ll lose everything. So he can press another button to cash out at any time. The idea is to see how big he’ll go before the balloon explodes or he bails. Then a new balloon begins to inflate.

During the game, Ted’s brain is processing several things: anticipation of reward, the reward itself, and the loss of the reward. For most “normal” people who’ve played this game in Poldrack’s lab, the loss sets off a reaction in the amygdala, the primitive part of the brain associated with fear and powerful emotion. “Most people do less. They’re risk-averse and they play it safe,” Poldrack explains as we stand behind a plate-glass window watching Ted.

“How are you doing, Ted?” Poldrack says into the speaker.

“So good,” he drawls in his best stoner voice. “This is, like, awesome.”

We watch the same screen as Ted. We watch when he scores points. The screen flashes 395. About average. We watch when the balloon explodes into dozens of pieces of shrapnel. We’ve turned off his mic, but I know that he’s in there cursing. Ted plays it again and again.

It is folly, of course, to draw definitive conclusions about the nature of human adventuring by looking at one man’s brain for 30 minutes. But it provides an interesting piece of the puzzle. The regions Poldrack and others are most interested in are the amygdala, home of fear; the prefrontal cortex, where we analyze decisions; and, increasingly, a part called the ventral striatum, or VS, located deep within the brain. Known to be one of the centers of the reward pathway, the VS houses many of our pleasure receptors. Scientists know that it’s intricately related to many other parts of the brain they just don’t know exactly how.

“We think this piece, the VS, adds zing a reward when we encounter novel things,” says Nathaniel Daw, of New York University. Daw’s research made a big splash last summer, causing some media outlets to declare the VS “the seat of adventure” because it lights up when volunteers make novel choices. But that interpretation is a bit too tidy, he says. In reality, the brain is highly interconnected, much like an ecosystem.

That zing, for example, appears to come from dopamine, a neurotransmitter made in the midbrain. Often called the pleasure molecule, dopamine is more accurately seen as a motivating signal, says Poldrack. Think of it as the angel or devil on your shoulder, goading you to get up early on a powder day or pull the lever on a slot machine. It is the brain’s elixir of desire.

Scientists know that dopamine is a key element in how and whether we seek stimulation, and that people’s “dopaminergic systems” vary widely. It’s long been suspected that the Terrible Teds of the world have lower dopamine levels, which may be why they’re easily bored and even miserable if they’re not doing their thing. But the differences between people may be less about overall dopamine levels than about the receptors that suck up the dopamine one of the main ways we keep a check on our desires. Last year, in one of the first experiments to measurably link dopamine differences to risk-taking behavior, Vanderbilt University researchers used a radioactive-imaging technique called positron-emission tomography (PET) to show that high-sensation seekers have fewer available receptors to vacuum up the dopamine once it’s released. Extra dopamine flooding the VS would explain the bigger high these thrill seekers get, whether it’s from drugs or skydives. When dopamine goes huge, people go huge.

Dopamine wiring is genetic, but we don’t know which genes affect it. Some high-risk takers have an extra-long gene for receptors called the DRD4. That gene, though, accounts for only about 2 to 3 percent of the variability among people. We also have differing levels of an enzyme called monoamine oxidase (MAO), which breaks down dopamine and appears to play an important role in regulating arousal and inhibition. Years ago, when Marvin Zuckerman was testing his high-sensation seekers, many showed unusually low levels of MAO. Interestingly, MAO increases with age, perhaps making us less pumped on adventure at the same time that our reflexes are declining. It also tends to be higher in women.

In any case, it appears that people like Ted are more sensitive to dopamine, making their highs higher and, perhaps, their lows lower. It’s as though they have bigger taste buds on their tongue. When they eat Pixy Stix, the sugary sweetness gets soaked up quickly, leaving them craving more. This is where it starts to look like addiction.

When I’d asked Ted how long his high lasts after a BASE jump, he said not long at all. “I even sometimes get depressed on the drive home.”

While we wait for the results from UCLA, another researcher is probing the minds of a few other adventurers: buddies Peter Konrad and Jacob Fuerst, swimmer Christopher Swain, kayaker Trip Jennings, and climber Steph Davis. The athletes dutifully fill out personality questionnaires that will be sent to professor of clinical psychology Carl Lejuez, director of the University of Maryland’s Center for Addictions, Personality, and Emotion Research and the inventor of the BART test.

The questionnaires cover the three main components of risk taking: sensation seeking, distress tolerance, and impulsivity. The questions are basic statements that you’re asked to either agree with or disagree with, such as “I go out of my way to get things I want” and “I would like to learn to fly an airplane.” Based on how you answer and how you play computer games in a scanner, Lejuez can come pretty close to predicting where you land on the thrill-seeking spectrum. If you’re in the red zone, he can even approximate whether you’re more likely to be useful to society or destructive. (Check out the masthead, on page 22, to see where members of ���ܳٲ������’s staff land on the scale.)

Most of our radsters rank high in one or two categories. Peter, the futon flier, is a very high-sensation seeker but average for the other two traits. Chris scores very high for impulsivity but on the low side for sensation seeking. Davis is average for sensation and impulsivity, high for distress tolerance. Trip and Jacob, meanwhile, are high-sensation seekers with average impulsivity and an admirably high tolerance for distress. “This, to me,” says Lejuez, “is what people think of when you discuss the outdoor-adventure guy who’s careful about the risks he takes and makes good decisions and prepares but just loves the rush.”

As for Ted—dear fringemaster Ted—he scores out of the ballpark on all three variables. Meaning, not only is he fearless and gung-ho; he’s also apt to make some doozy mistakes. A classic high-sensation seeker, he drives fast; he listens to loud music; he’s done his share of illicit substances and had his range of girlfriends, although Amber has been in the picture for four years. (She gave him the perfect anniversary gift: a SPOT emergency GPS locator, so that if he’s ever hurt, he can just press the big 911 button.) In other words, as inspiring as it is to watch him on skis, you wouldn’t really want him commanding NATO forces.

And when the UCLA results come in, they beautifully confirm Ted’s gold-star gnar-gnar status. Poldrack is excited. The images are high-quality, meaning our boy stayed very still in that tube. Moreover, Ted’s brain responded in pretty much the exact opposite manner of most people tested, especially during the balloon explosion. While other people’s brains show activation in the amygdala, where fear resides, Ted’s is blank. Instead, a small, Australia-shaped red patch the ventral striatum is lit up, which doesn’t happen with most people.

So there you have it: Ted’s brain revealed. High rewards for risk, no fear of its consequences. Mystery solved. Or is it?

Not quite. Based on Ted’s answers, Lejuez would have predicted him to be freebasing instead of freeskiing. Ted admits that he’s an addictive type. “I’d probably be doing heroin if I weren’t jumping,” he says. “In college I was like, let’s get napalmed! But now I’d so much rather be getting up early getting ready for a jump. It’s like a drug to me. I crave it.”

And, if you discount all those emergency-room visits, his is a relatively healthy form of self-medication. “Guys who are jumping off cliffs or who are workaholics may be just as abnormal as someone who’s addicted to cocaine,” says Jerome Kagan, emeritus psychology professor at Harvard. “But as a society, if you’re not unhappy, we don’t tend to regard you that way. These people have found an activity that gives them great pleasure, that improves their quality of life, and that keeps them in a good mood and out of trouble. A lot of us never find that.”

In the end, throwing 1080’s may have saved Ted. He took his relict brain, plunked it in a helmet, and faced it toward the mountains. But what about the rest of us? Is biology or, in this case, neurobiology destiny? Can people edit their brains, conditioning themselves to be more or less adventurous?

“Absolutely,” says Lejuez, who often works with troubled, high-risk-taking youths. It turns out that our brains are pretty plastic, regardless of the hard-wiring. If we tend to be reckless, for example, we can learn to keep impulsiveness in check. If we’re anxious, we can slow our breathing in times of fear, and even arrest the shakes of adrenaline the dreaded sewing-machine leg while climbing an exposed route. As we become more skilled and experienced, our comfort zone expands.

“I feel fear causes bad situations,” says Steph Davis, who’s trained herself to control her fear through rigorous preparation. “Since I started BASE-jumping, I do more assessing in advance. I make decisions ahead of time. Where’s the out? I need to organize all that before I even jump.”

And, of course, there’s aging, something most of us, fortunately, get to do. “I've definitely mellowed,” says Trip Jennings, who, at 26, is two years younger than Ted. “I can see it in my style of kayaking as well. The adrenaline of big drops has given way to exploring new rivers. It’s got to have an environmental or socially significant part to be a project that’s meaningful.”

Did Trip mold his brain chemistry or did his chemistry predetermine how nicely he would mature? And will Ted’s brain mellow, too?

Frankly, we don’t have much of a clue.

What we do know is that everyone’s brain looks different. We’re all shaped by values, experience, and ineffable luck as well as by our genes. As Poldrack puts it, “There’s no single gene and no single protein related to any one behavior. There is a big cascade of lots of biological processes interacting with the environment that enables a person to be thrill-seeking.” In other words, despite all the fancy scientific inroads, the call of adventure is still a big mystery.

And that, after all, is part of the fun.