So, this is reality? They're cheap to produce and feed our appetite for snooping. No wonder reality shows are filling up the television airwaves. (arts).

It was the sort of intimate family conversation that, until recently, would never have been filmed as television entertainment. Aging rocker Ozzy Osbourne was confronting his 18-year-old daughter, Kelly, about her real-life partying ways and alcohol use on his hit MTV show The Osbournes.

"Kelly, we're not in England," the marble-mouthed Osbourne lectured, "we're in the United States of America, and the laws of California say you have to be 21 to drink." The advice--from a man who has taken more than his share of drugs--didn't exactly sink in. That evening, the cameras caught an inebriated Kelly twirling in circles, and falling to the floor. "I'm going to be sick," she said.

It was all just another day in the life of reality TV, the fastest-growing genre of programming on television. A seemingly endless supply of ordinary people--and more recently, faded celebrities--are volunteering to let cameras follow their every move at home, on a deserted island, or during a romantic encounter. It's a bit like the 1998 movie The Truman Show, in which TV producers film the entire life of a man played by Jim Carrey. Only the Carrey character didn't willingly subject himself to the intrusion.

Reality shows--from Boot Camp and Big Brother to Joe Millionaire and The Bachelor--now fill prime time slots on all the major broadcast networks. In fact, 5 of TV's top 20 programs are reality series, and many more are on the way.

There is nothing new, of course, about people's fascination with watching each other. Television has been satisfying society's nosiness since Candid Camera debuted in 1948. The appetite for observing others in unscripted, unrehearsed moments is in our genes, says Robert Thompson, director of Syracuse University's Center for Popular Culture. "There were cave people who peeped into the caves of their neighbors," he says. "We're genetically encoded to wonder what other people are up to."

The modern version of reality TV had its genesis in 1973 when PBS aired An American Family, which chronicled the hardships of a California family. In the 1980s came the debut of MTV's The Real World, which put a group of 20-somethings together in a Manhattan loft apartment, unscripted, with cameras rolling. They heatedly debated abortion and racism, discussed personal problems, and broke down in teary confessional interviews.

But it wasn't until the blockbuster arrival of Survivor on CBS in the summer of 2000 that reality TV proved its mass appeal. Survivor broke viewing records when millions tuned in to watch 16 people trying to cope with being stranded on a deserted island.

LOW COST, HIGH RATINGS

One reason why the genre has multiplied is that reality shows produce big profits. Watching Ozzy Osbourne take target practice with butter knives in his backyard may seem trivial, but such antics draw young viewers with disposable incomes. Taco Bell, Blockbuster, and Levi's pay handsomely to pitch their products to the audience they want to reach the most.

Reality shows with casts of unknowns also are far less costly to produce than, say, hit sitcoms, for which stars' salaries can run more than a million dollars per episode.

So far, some of the most successful reality TV shows have focused on dating. About 20 reality dating series are on the air. "Most of the information people have on courtship comes from firsthand experience," Thompson says. "Dating is intimate, private behavior. So viewers who eavesdrop on The Bachelor are learning things about dating they might not pick up elsewhere." That may explain why 26 million people tuned in the night bachelor Aaron Buerge proposed to Helene Eksterowicz on the ABC show The Bachelor.

Despite their popularity, reality shows have caused their share of controversy. Cast members of some shows--including The Osbournes and Survivor--have accused producers of trying to influence their behavior to generate a more entertaining "reality." The shows have denied doing so, though Survivor acknowledged restaging some scenes with body doubles.

The pressure to keep an audience can be fierce Ratings for reality shows usually drop after a new series launches. Producers--buoyed by the success of The Osbournes, MTV's most-popular show ever--have tried to keep the genre fresh by turning to celebrities.

CELEBRITIE'S REAL WORLD

Most are decidedly B-list. On The Anna Nicole Show on E! Entertainment Television, cameras follow the bizarre ramblings of Anna Nicole Smith, a former model who married an 89-year-old oil billionaire and is now living off the money he left her in his will.

One of the newest entries, the WB's Surreal Life, features a group of career-challenged celebrities like MC Hammer and Corey Feldman trying to get along under one roof.

Of course, if celebrities start to reveal their private lives, warts and all, it would signal a shift in American celebrity culture. Sixty years ago, movie studios did everything they could to keep news of a star's drunk driving arrest or a major illness out of the press. Now it's fodder for ratings.

But apart from the success of The Osbournes, celebrity reality shows aren't capturing the interest of viewers, says Andy Dehnart, who tracks two dozen reality TV series on his Web site, realityblurred.com. "The success of reality TV comes from making ordinary people stars, not building shows around those already famous," he says.

Just how long will the eavesdropper in all of us stay tuned?