Children's television reportedly contains up to 25 acts of violence in a single hour--content that may have serious behavioral ramifications on its young viewers, researchers report. According to a study published in the current issue of the journal Science, adolescents who watch more than one hour of television a day are more likely to engage in violent or aggressive acts later in life. This link was strongest for boys, but dedicated adolescent viewers of both sexes were more likely to act aggressively toward others in their late teens or early twenties than those who abstained or watched very little television. Additionally, the researchers uncovered an apparently direct correlation between the amount of time spent glued to the entertaining screen and the likelihood of subsequent misbehavior.

Jeffrey Johnson of Columbia University and colleagues conducted a series of interviews with a group of more than 700 children and their parents over a period of 17 years beginning in 1975, when the kids were 10 years old or younger. The team gathered data on both the television viewing habits and behavior of the subjects as they aged. Interviews aimed at evaluating aggression continued through the year 2000, when the researchers also consulted state and federal records for instances of criminal behavior. Even after adjusting for factors such as parental education, psychiatric conditions and safety of the subject's neighborhood, the link between television exposure and aggressive behavior held up. Indeed, 22.5 percent of adolescents who watched between one and three hours of television a day committed aggressive acts later in life, compared with 5.7 percent among those who spent less than one hour in front of the tube. For the individuals who watched more than three hours, the number jumped to 28.8 percent. As for the nature of their violent actions, boys most often engaged in assaults or fighting; aggressive acts amongst young women included robbery and harmful threats.

"Our findings suggest that, at least during early adolescence, responsible parents should avoid permitting their children to watch more than one hour of television a day," Johnson says. He also took care to note that scientists suspect a range of ill-effects from over-exposure to television in young people, including greater chances of obesity.