Research by the Kids Risk Project at the Harvard School of Public Health found a "ratings creep" for movies, and suggested that the Motion Picture Association of America was relaxing standards in rating films.
The study, released Tuesday, suggested that films rated parental guidance, or PG, and parental guidance for children under 13, PG-13, had become more violent. There was more sexual content in films rated PG, PG-13, and R, which requires children under 17 to be accompanied by a parent or adult guardian. More profanity was used in films rated PG-13 and R, the study found.
The researchers said the current U.S. rating system does not adequately describe the contents of movies.
"It's time for a significant research effort to explore the development and creation of a universal media rating system," Kimberly Thompson, the associate professor who directs the Kids Risk Project, said in a statement. "Parents and physicians should be aware that movies with the same rating can differ significantly in the amount and types of potentially objectionable content."
The study also found more violence in animated films rated G — for family viewing — than in non-animated films with the same rating and emphasized that animation doesn't guarantee appropriate content.
"Parents must recognize their responsibility in choosing appropriate films with and for their children, and in discussing the messages in films with children to mediate any potential adverse effects and reinforce any potential beneficial effects," the study said.
The MPAA recently chose former Agriculture Secretary and congressman Dan Glickman as its new chief, allowing the resignation of Jack Valenti after 38 years in the job. Valenti, however, will continue to supervise the voluntary film rating system, which he devised in 1968.
By coincidence, Glickman has spent the three years since he left the government as Director of the Institute of Politics — also at Harvard.