Is a teenager's propensity for doing really stupid things inevitable, or must that stupidity be coaxed out of him? That's the question asked by neurosurgeons at Case Western University School of Medicine in Cleveland, Ohio.

The research team examined the reckless yet increasingly popular "sport" of car surfing, in which the passenger or sometimes driver opts for the more spacious view on the hood or roof of the car while the car is moving.

Their research, however, turned into something deeper than a typical neurological injury study that merely reports the unsurprising laundry list of head injuries inherent from being tossed from a moving vehicle into a gravel-filled ditch or onto glass-strewn asphalt. They asked why anyone would undertake such risky behavior.

Spikes in car-surfing injuries during the past decade, they found, neatly overlap the release of video games and movies depicting the act. These results appear in the July 2009 issue of Journal of Neurosurgery: Pediatrics.

Seatbelts are for sissies

American high school students were never that good at physics, or car-surfers would first do some back-of-the-envelop calculations. The fastest that a typical kid could run into a wall, should that sound appealing, is about 15 mph. This modest foot-powered collision would hurt, although I admit I cannot cite any study here.

But on the hood of a car and at the moment of the inevitable departure from the aforementioned hood, the surfing passenger is moving at the same speed as the car, typically 25 miles per hour or more.

In their retrospective study, the Case Western researchers found that 100 percent of the car-surfing injuries treated at their hospital, Rainbow Babies and Children’s Hospital, were cranial injuries such as skull fractures. In comparison, the risk of cranial injury from "normal" car or bike accidents, they found, was about 25 percent.

Saw it on TV

The first reports of car surfing as a phenomenon emerged in the 1980s. Copycats were inspired by the 1985 movie "Teen Wolf," in which the lead character hops on the hood of a moving car to the tune of "Surfin' USA." Mercifully, "Teen Wolf" faded quickly from everyone's memory, and car surfing faded, too.

But by the end of the 1990s, car surfing was back — and with it the injuries and fatalities. The Case Western researchers examined statistics from the three states with the highest car-surfing fatality rates: California, Florida and Texas. The resurgence, the study found, aligns perfectly with its depiction in popular media.

The first major rise in fatalities from 1998-1999 overlapped the release of the first two editions of the "Grand Theft Auto" video games. A second major rise in fatalities between 2000 and 2002 occurred with the release of "Grand Theft Auto 3," "Grand Theft Auto: Vice City," and MTV's "Jackass" series and movie. A third peak came around 2005 with the introduction of "Grand Theft Auto: San Andreas" and a proliferation of self-made videos of car surfing on YouTube.

Conversely, the researchers found, during the years with no new edition of "Grand Theft Auto" or "Jackass," there was a drop in car-surfing fatalities.

Evolution of recklessness

So who is at fault? In a commentary on the car-surfing article, Ann-Christine Duhaime of Dartmouth-Hitchcock Medical Center in Lebanon, N.H., explains that teenage risk-taking is likely a result of immature brain formation — "a relative surfeit of limbic drive at a time when frontal circuitry, and its attendant cautious oversight, is incompletely functional."

And this clearly unproductive propensity to crack your head open during a period when the body is otherwise trying to be productive — that is, mate — can be explained in the context of evolutionary theory, Duhaime said. Without the unjustified feeling of confidence to control fate and cheat death, adolescent animals might never leave home to seek new territory and mate.

Nevertheless, the Case Western study reveals that while some stupidity among teenagers is to be expected, really, really stupid ideas come from the popular media. This implies that game makers and television producers should assume the viewer can and will try this at home.

Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His column, Bad Medicine, appears each Tuesday on LiveScience.