Four teenagers in a car pull up next to a man on a bicycle traveling 30 miles per hour. One of the teens leans out the window of the car and pushes the man off his bicycle. The car speeds away, all four teenagers laughing. The bicyclist suffers broken ribs and a punctured lung. Witnesses get the license number of the car and the kids are tracked down. None of them have been in trouble before; the one who pushed the bicyclists is considered a very good student.

Four teenagers cruising in a car--a different group this time and one composed of "average students" who've also never been in trouble before--spot two students from a rival high school walking to a nearby convenience store. One of the pedestrians is on crutches, his foot wrapped in a bandage. The four teens pull over, pile out of the car, and attack the two boys. They punch the healthy one in the face. The other boy is not so lucky. They steal his crutches, beat him with one, and hit him with a small baseball bat. Once he's on the ground, one of the assailants stomps on his head.

The boy on crutches--formerly an athlete--is now in the hospital. He's paralyzed on the right side of his body. His doctors think he may recover, but they can't be sure. Head injuries can be tricky. Sometimes the patient makes a full recovery. Sometimes he or she recovers a bit and that's all. Sometimes the patient never recovers much use of his or her body or mind. Always the patient is left wrestling with his or her health for years, if not the rest of a lifetime.

Two of the attackers were appalled to see the extent of the boy's injuries and turned themselves in to police. How could they not have known what the consequences of their actions would be?

Simple. It's all too easy these days for anyone to underestimate the effects of violence on another person.

We can start with Hollywood, which has a big impact on teenagers, who consume the bulk of movies released in any given year. Hollywood violence falls into two categories: the outright kill (usually of a bad guy), and the not-even-a-scratch-left-on-him (usually the good guy). There is no in-between: no scenes of families in the hospital being told by the doctor, "he has a blood clot in the left temporal lobe of his brain," or "she has a fractured vertebra and no sensation in her legs."

A case in point is the recent movie "Panic Room." Reviewers gave it a unanimous thumbs-up, and described it as a suspenseful thriller in the Hitchcock mode. Some even called it "smart" and "realistic."

In fact, it's absurd. There are numerous scenes of physical violence in the film, all of them about as realistic as a Sylvester and Tweety Bird cartoon. In one particular scene a man is beaten so severely that without an immediate trip to an emergency room, he would die. Perhaps he would linger unconscious and in a coma for a while, but there's no doubt that he's a dead man. His assailant kicks him in the head--in the face, in fact--numerous times. Yet, minutes later, he's sitting up in a chair, awake, talking, with a broken arm and some blood on his face. Improbably, his nose is still there, his jaws still attached and working properly. Impossible. He's one of the good guys, of course.

Why do we wonder that our teenagers have no comprehension of just how fragile the human body is? Coked-out script writers and Hollywood producers haven't got a clue, either. And they spread their ignorance with each piece of slick, pornographically-violent "entertainment" they produce.

What about recent, "realistic" war movies? Oddly, certain types of on-screen violence are deemed unsuitable for teenagers, hence the NC-17 rating. Those depictions, naturally, show the realistic effects of being shot. Arguably, a 13-year-old should see what it's like to shoot someone or get shot. He or she might chose to not carry a handgun to school.

It's not just Hollywood that's to blame; that's too simple an argument. Teenagers have other influences. For example, video games with modern graphics look more realistic every year. They still, however, retain the video-game ethic of endless fighting without realistic injuries.

Video games, of course, are fantasy. After all, the bad guy is often some weird alien or monster that doesn't exist in the real world. Their purpose is to entertain, not educate. But violence as entertainment--even against a made-up monster--is a problem. Violence in the real world is never entertaining, except for the assailants that we label "psychotic." Such people have lost or never had the ability to understand the pain they inflict on others. They have no empathy.

When we expose young people with limited experiences of life to unrealistic depictions of violence and tell them that it's fun, are we turning them into psychotics? Many American teenagers have never been seriously injured, felt real pain, seen a loved one die or experienced a lingering illness. They know what it's like to stub a toe, get a paper-cut, or skin a knee. They don't know what it's like to get hit in the head with a baseball bat. In fact, many American adults don't know what that's like.

As a society we need to talk more about violence and its effects. We need to talk one-on-one, at work, at school, at home, on the radio, on TV, and in the newspapers. We need to hear about what happened to the victims, read the gritty eyewitness accounts, see bodies lying in the streets and on the battlefields. We need to refuse the urge to protect ourselves and our children from "the unpleasant truth"--whether it happens in our own neighborhoods, in New York City, or in the Gaza Strip. Knowledge is power; in this case, the power to protect ourselves and our kids from one-on-one, senseless, thrill-seeking violence.