For much of the past half century, the link between watching violence on television and violent behavior in everyday life has seemed an open question embraced by one study, rejected by another, and largely left unanswered by years of congressional inquiries.
That, however, is rapidly changing. To a growing number of scientists and psychiatrists, the correlation between the two is no longer a point of debate, it is an established fact.
A study released today in the journal Science adds to a large body of work that suggests some sort of connection. Already, six major pediatric, psychiatric, and medical associations have said that the evidence of a link is overwhelming, citing more than 1,000 studies in the past 30 years.
As a result, the debate is increasingly splintering into a fight that echoes the recent antitobacco or global-warming campaigns, as a preponderance of scientists square off against a besieged industry and a smattering of contrarian colleagues.
Many Americans are not yet convinced. On average, children still watch three hours of television a day, and calls to regulate the industry have resulted only in minor tweaks like the current ratings system. But with the scientific community presenting a more unified front and casting the issue as one of public health, not taste the pressure for more change is gaining momentum.
"Clearly, with more exposure [to media violence, children] do become desensitized, they do copy what they see, and their values are shaped by it," says Susan Villani, a Baltimore, Md., psychiatrist who has reviewed the past 10 years of study on the subject.
Not even the most ardent critic of TV violence argues that images of gunplay and kung fu are the sole causes of youth violence. Yet they can be significant.
One study last year found a 25 percent decrease in violence in a San Jose, Calif., grade school where kids received classroom lessons in media awareness and were asked to watch only seven hours of TV a week for several months. Another in North Carolina showed that teenage boys who regularly watched professional wrestling were 18 percent more likely to get into a physical confrontation with a date.
Today's study, experts say, is particularly interesting for several reasons. It is the first survey of its scope to provide evidence that violent behavior is associated with television viewing beyond childhood well into adolescence and adulthood. In addition, it claims a connection even when other factors such as childhood neglect and low family income are taken into account.
"What this study serves to do is remove some of these variables," says Michael Brody of the American Academy of Child and Adolescent Psychiatry.
Adolescents who watched more than one hour a day of television regardless of content were roughly four times more likely to commit aggressive acts toward other people later in their lives than those who watched less than one hour. Of those who watched more than three hours, 28.8 percent were later involved in assaults, robberies, fights, and other aggressive behavior.
The study, led by Jeffrey Johnson of Columbia University in New York, followed 707 participants in upstate New York for 17 years, recording their TV viewing habits and tracking their behavior through periodic interviews and public documents.
What it did not do, say critics, is prove that the television viewing necessarily caused the violence. The comment goes to the heart of the debate over the issue: Does TV play a part in making violent people, or are violent people naturally inclined to watch violence on TV?
"I don't think there is any link at all," says Jonathan Freedman, a professor at the University of Toronto who disputes the statistic that thousands of studies have shown a link between television violence and violent behavior.
Members of the broadcasting industry share Mr. Freedman's skepticism of such media studies. "They spark a lot of interest, but nothing definite comes out that can establish a direct link," says Dennis Wharton of the National Association of Broadcasters in Washington.
The industry also touts their cleaner fare: A recent study by the Center for Media and Public Affairs in Washington found a 29 percent drop in TV violence last season compared with 1998-99.
Aspects of the criticism find broader support. It's true that some kids might be able to watch TV all day and not commit a single violent act. But some psychiatrists say that merely begs for more research about who might be influenced by TV and how.
But most also insist that the vast majority of studies support a link. Granted, no study can definitively say that TV caused a violent act it can only infer. But the results of one of the most researched areas in social science are pretty consistent, says professor Craig Anderson of Iowa State University in Ames. "It doesn't matter how you study it, the results are the same," says Mr. Anderson.
Plus, for many, it's simply a matter of common sense. "If television doesn't influence kids, then why are so many people spending so many billions of dollars to advertise," says Dr. Brody. "It's not the sole cause, but even if it represents 10 percent of the reason [for violence], somebody should look at this."