Scenes of stabbings, shootings, rape, decapitation and mutilation invariably received a TV-14 "parents strongly cautioned" rating on network TV, according to the Parents Television Council study released Monday.
But similar fare on cable typically was given the most stringent label, TV-MA for mature audiences only, researchers for the media watchdog group found.
"There are zero-point-zero series rated TV-MA on broadcast," said the media watchdog council President Tim Winter, despite programs that are awash in violent scenes.
It is vital to examine the media's effect on children and real-world violence, Winter said, adding that he hopes his nonpartisan group's findings are part of a wide-ranging search for solutions.
The study of 14 series during a four-week period found a 6 per cent difference in the overall incidence of violence of all types on cable versus broadcast, with 1,482 violent acts on the cable programs and 1,392 on the network series.
Federally regulated broadcasters face sanctions if they cross the line on indecency or expletives, but not violence. With competition from unregulated cable and its variously daring series such as "Breaking Bad" and "Masters of Sex," networks have resorted to more mayhem.
Episode ratings are decided by networks and cable channels, similar to how the movie studios' Motion Picture Association of America self-governs by issuing its own movie ratings. The TV Parental Guidelines Monitoring Board, comprised of TV industry members and public interest advocates, checks for ratings uniformity and responds to public complaints. It received 38 complaints in the past year.
The ratings system "serves as a valuable resource for parents and helps them make responsible viewing decisions based on what is appropriate for their own families. The industry regularly reviews the TV ratings to ensure they continue to be useful to parents," Missi Tessier, spokeswoman for the board's executive secretariat, said in response to the PTC study.
NBC, CBS, Fox and CW did not comment on the study, which did not include any ABC shows.
Under political and social pressure in the mid-1990s, the voluntary system was established by the TV industry to be used with the so-called V-chip that can block shows electronically.
Networks find it financially vital to avoid applying TV-MA ratings, Winters said, which scare off advertisers.
To assess how the ratings are used, the PTC said it analyzed the seven shows each on cable and broadcast TV that had the highest levels of violence. Each show's first four episodes of the 2012-13 season were analyzed.
TV-14 warns that a program may include intense violence, sex or language not suitable for children under 14, while TV-MA is intended for shows that might have indecent language, graphic violence or explicit sexuality, according to the TV Parental Guidelines webpage.
The PTC study defined graphic as "especially vivid, brutal and realistic acts of violence" that are explicitly depicted. Among the network examples cited:
— A bar fight scene on NBC's "Revolution" in which a character wields a sword and a dagger to slash open one man's chest, cut another's neck and stab a third in the chest. The blood-spattered character pulls his sword from the last victim's body.
— CW's "Supernatural," in which a trail of blood leads to the bodies of two priests impaled on a cemetery's wrought-iron fence. Their eyes have been gouged out and blood drips down their faces.
— A woman is tortured in captivity, with an implanted camera sending images of her agony online in an episode of CBS' "Criminal Minds." An FBI agent watches as a hammer is driven into the victim's head.
Depictions of shootings, stabbings and dismemberment were found on cable shows including AMC's "The Walking Dead" and "Breaking Bad" and FX's "Sons of Anarchy." Five of the seven cable shows had TV-MA ratings, with "Walking Dead" eventually switching from TV-14 to MA.
Other broadcast shows in the study included NBC's "The Blacklist," Fox's "Sleepy Hollow," CBS' "CSI" and NBC's "Law & Order: Special Victims Unit."
Although administered differently, movie ratings have also been criticism for being soft on violence. A study last month found the number of scenes featuring gun violence in PG-13 movies has come to rival or surpass the rate of such action in R-rated projects.
The PTC's Winter said his group's study, taken together with the movie report, "starts to weave together a fabric that urgently needs a public response."
Lynn Elber is a national television columnist for The Associated Press. She can be reached at email@example.com and on Twitter@lynnelber.