If everyone else jumped off the Brooklyn Bridge, would you?

Several recent incidents, including the April 27 arrest of Jeb Ray Corliss IV, who was caught by police as he prepared to skydive off the Empire State Building’s observation deck during rush hour, have called attention to BASE jumping, a fringe sport that’s been around since the early 1980s.

The “BASE” in BASE jumping is an acronym that stands for the four locations a skydiver must leap from before he can call himself a BASE jumper: Building, Antenna, Span (in other words, a bridge) and Earth (i.e., a cliff).

And the action isn't limited to New York City. On May 10, two men were arrested and charged with disorderly conduct after they parachuted off a 300-foot-tall Union Pacific Railroad communications tower in Waterman, Ill.; and on Wednesday, a Belgian BASE jumper successfully jumped off the top of the Eiffel Tower after a Norwegian man died attempting the same stunt a year ago to the day.

But why would anyone in his right mind want to jump off a building?

“BASE jumpers, like most adventure seekers, are motivated by a variety of things,” said Tom Buchanan, a Vermont-based skydiving instructor who’s been a BASE jumper since 1986. “Some are attracted to the risks and enjoy working to minimize those risks.

"Some accept the risks and treat BASE jumping as a wild game of Russian roulette. Some are intrigued by the illegal side of the sport and enjoy the cat-and-mouse aspect of getting away with jumps. Some are ego-focused and groove on the notoriety of their involvement. Some are very normal people who simply take skydiving up a level, and appreciate the thrill of meeting an exceptional challenge.”

What makes BASE jumping so much more challenging — some would say insane — than conventional skydiving is that it takes place at very low altitude, with many more dangers than a parachutist faces when he jumps out of a high-flying plane over an empty field.

“It has to do with the height from which they’re jumping, the conditions and the amount of hazards that are in the way,” said Dr. Jeff Kalina, associate medical director of emergency medicine at The Methodist Hospital in Houston, Texas.

“For example, when you’re skydiving in a wide open space, there’s room for error, though not a whole lot. BASE jumping is in a smaller area where there are hazards like rock ledges, tree limbs, etc., plus the time you have to open a chute is narrower."

Buchanan said BASE jumping can be a one-shot deal — you get it right the first time or you get killed or seriously injured — but not always, if managed responsibly and correctly.

“It is relatively unforgiving sport, for sure, but there is some margin for error, depending on objects and the way you approach the object,” he said. “If the object is 250 feet tall, you have no margin for error if you screw up. If it’s 3,000 feet tall, there’s lots of room for error.”

Buchanan and Kalina agreed that, generally speaking, the most dangerous of the four goals of BASE jumping is the kind of attempt Corliss — who was disguised in a fat suit and $15,000 mask and wig — made in New York City.

"Once you start getting amongst buildings, wind tunnels and wind directions and wind shears, you can’t predict what’s going to happen,” Kalina said. “I’m sure you’ve been walking down the street and you get between two buildings and the wind generated between the two buildings can be a lot greater than the recorded wind velocity that might be away from the buildings — it’s a tunneling effect of tall buildings.

"Plus you have the convection effect of the heat generated from the city streets. So you get tremendous wind shear and unpredictable conditions, plus a very narrow area for error. If the wind puts you 3 degrees off target, you could slam into an awning or another building or an antenna or into someone’s board meeting."

Corliss’ stunt brought much negative media attention to BASE jumpers, many of whom distanced themselves from the Empire State Building attempt, which would have risked not only Corliss' life but also those of countless New Yorkers and tourists packed into Midtown Manhattan on a weekday afternoon.

“It was reckless, without any question,” Buchanan said. “It didn’t mean that jumping from the Empire State Building must be reckless, but he didn’t do anything to mitigate those risks. ... Most BASE jumpers are extremely smart and focused on safety. Most of it happens without any injury or the knowledge of the authorities. (The clean getaway is considered an integral part of the urban BASE-jumping experience.)

"The jump at the Empire State Building was an aberration because it was very public. It’s not fair to say that everyone in BASE jumping is a glory grabber.”

Yet the lure of a potentially deadly jump can be irresistible, as Buchanan learned in the early 1980s, when he was a seasoned skydiver looking for new challenges.

“I was a skydiver, and New River Gorge Bridge (in Fayetteville, W. Va., which has an annual, legal BASE jumpers’ “Bridge Day”) was beckoning,” he said. “It sounded like something where I could go try and push myself, and as a skydiver I felt like I had pretty well peaked and was looking for new things to try. Once you make a BASE jump, it kind of sucks you in. It’s a unique experience.”

Rebecca Aronson, a graduate student at Northwestern University's counseling-psychology program, said some research has pointed to “thrill-seeking” genetic and neurochemical factors that might explain why some people are attracted to the kind of behavior that most people consider nearly self-destructive.

Some researchers have theorized that low levels in the brain of monoamine oxidase, linked to the sensation of pleasure, might be responsible, leading to the idea that some people might actually be “addicted” to thrills much in the way others are addicted to drugs.

“I would say that thrill addiction is possible, given the high amount of pleasurable sensation that a person would achieve by successfully completing an exciting or risky task,” Aronson said. “Furthermore, he or she may be egged on by others to continue such behavior, whether it's to break an extreme sport record or by succumbing to peer pressure to get high on drugs.”

And there might be a societal factor at play as well, she said.

“Culturally speaking — and there's been a lot written about this — one might ask if the craze over extreme sports represents a new strain of American ‘rugged individualism,’" Aronson said. “Does the impulse to parachute off of a building represent some urge to individuate in a society that is conformist and fixated on safety?”

If it is a reaction to a mothering society, Buchanan said, it’s not one that’s growing any bigger.

“Participation in BASE jumping is probably stable,” Buchanan said. “It may climb a little bit, but not a lot.”

In recent years — perhaps because of the growing expense of an already costly sport or the dwindling amount of free time Americans have — the rolls of registered skydivers have shrunk noticeably.

Most BASE jumpers are drawn from the pool of skydivers, so as the average skydiver gets older, so does the average BASE jumper. But that also means the average jumper is more experienced and mature, Buchanan said.

That, plus the increasing number of legal locations to BASE jump, could mean there will be fewer hot-dog stunts like the ones in Illinois and New York.

“Most BASE jumpers would rather jump from legal objects, or jump quietly from objects that may not be quite so legal,” he said. “The ESB jump is just not in the sights of most BASE jumpers ... and probably will not be repeated again for many years.”

But BASE jumping, Buchanan said, will never be ordinary.

“BASE is a very dangerous and unforgiving sport," he said. "And that alone will prevent it from ever becoming mainstream.”