Risk

Many climbers fit the HSS profile. Many report difficulty keeping full-time jobs, either because the work bores them, or because it interferes with their climbing schedule. Long-term relationships can be problematic, especially where climbers marry nonclimbers, or where one partner begins losing interest in the sport. Non-climbing partners often complain that their spouses spend too much time away from home, or refuse to commit to projects (children, for example) that might interfere with climbing. Relationships are also strained by the ever-present threat of injury or death. As one Midwestern climber puts it, "the possibility that I might miss dinner, forever, doesn't make things any smoother."

Further, while many climbers are models of clean living, the sport has its share of hard partiers. Some even boast of making first ascents while high on marijuana or hallucinogens like LSD. Climbers say such drugs enhance or intensify the climbing experience. But studies suggest that the drugs may also mimic the process that pushes climbers in the first place.

WIRED FOR THRILLS

Researchers have long known of physiological differences between high- and low-sensation seekers. According to Zuckerman, the cortical system of a high can handle higher levels of stimulation without overloading and switching to the fight-or-flight response. Psychologist Randy Larsen, Ph.D., at the University of Michigan, has even shown that high-sensation seekers not only tolerate high stimulus but crave it as well.

Larsen calls high-sensation seekers "reducers": Their brains automatically dampen the level of incoming stimuli, leaving them with a kind of excitement deficit. (Low-sensation seekers, by contrast, tend to "augment" stimuli, and thus desire less excitement.) Why are some brains wired for excitement? Since 1974, researchers have known that the enzyme monoamine oxidase (MAO) plays a central role in regulating arousal, inhibition, and pleasure. They also found that low levels of MAO correlate with high levels of certain behaviors, including criminality, social activity, and drug abuse. When Zuckerman began testing HSS individuals, they, too, showed unusually low MAO levels.

The enzyme's precise role isn't deal It regulates levels of at least three important neurotransmitters: norepinephrine, which arouses the brain in response to stimuli; dopamine, which is involved with the sensation of pleasure in response to arousal; and serotonin, which acts as a brake on norepinephrine and inhibits arousal. It's possible that high-sensation seekers have lower base levels of norepinephrine and thus, can tolerate more stimulation before triggering serotonin's dampening effect. High-sensation seekers may also have lower levels of dopamine and are thus in a chronic state of underarousal in the brain's pleasure centers.

Such individuals may turn to drugs, like cocaine, which mimic dopamine's pleasure reaction. But they may also use intense and novel stimulation, triggering norepinephrine's arousal reaction and getting rewarded by the dopamine pleasure reaction. "What you get is a combination of tremendous arousal with tremendous pleasure," Zuckerman speculates. "And the faster that arousal reaches its peak, the more intense your pleasure." Just as important, individuals may develop a tolerance for the pleasure reaction, and thus may need ever higher levels of stimulation--of risk--to achieve the same rush.

Today such an addictive dynamic may seem largely problematic. In prehistoric times it was very likely essential. Dopamine, for example, has known links to various "approach" behaviors: feeding, fighting, foraging, and exploration. Probably, the same mechanism that gave people like Derek Hersey a rush from climbing also rewarded their predecessors for the more necessary acts of survival.

Psychologist Aptor suggests that the willingness to take risks, even if expressed by only certain individuals, would have produced benefits for an entire group. Upon entering a new territory, a tribe would quickly need to assess the environment's safety in terms of "which water holes are safe to drink from, which caves are empty of dangerous animals." Some risk takers would surely die. But, Aptor points out, "it's better for one person to eat a poisonous fruit than for everybody."