WASHINGTON — A group of researchers claims in a study released here Wednesday that they have uncovered a new phenomenon related to the television industry’s age-based content code: the Forbidden Fruit Effect.The ratings system was designed to help parents guide the viewing habits of their children, but kids may instead be using it to find the raciest programs on TV, researchers say. “The rating system now being implemented has been shown to attract many children to restricted programs,” Joanne Cantor of the University of Wisconsin said. Cantor is a lead researcher in a $3.3 million study financed by the National Cable Television Assn. The study is spearheaded by UC Santa Barbara. On Wednesday, researchers released the second installment of the three-year study. As they did last year, researchers found that a majority of television programming includes violent programming. They also found that there has been no significant change in the level of violent programming during the past two years. The cable industry financed the study under pressure from Capitol Hill two years ago. Broadcasters have financed a separate study of their own. Despite the industry’s efforts to placate Beltway culture warriors with studies and rating systems, TV content issues continue to get top billing. Even President Clinton got into the act Wednesday, releasing a statement praising the study and calling for a reduction in the amount of violence on TV. “Today’s study shows there is still too much violence on the television, and that we must all continue the important work we have begun,” Clinton said. Cantor did not study the television industry’s “Parental Guidelines” rating system. Instead she based her theory on an experiment conducted with 374 Milwaukee children aged 5-15 who used the Motion Picture Assn. of America’s rating code. The TV code now in use is based on the MPAA’s age-based code. Cantor also tested the kids’ reactions to seven content-based systems, such as the ones used by HBO and Showtime, which indicate the level of sex, violence and adult language in a program. Out of the eight program ratings systems studied, the researchers found that only the MPAA code encouraged kids to watch programs created for more mature audiences. “The more restrictive ratings of PG-13 and R increased a program’s attractiveness, and the lowest rating, G, decreased it,” the researchers wrote. MPAA prexy Jack Valenti was quick to defend the rating system he created for the movie industry almost 30 years ago. “Now, let’s get this straight. A program rated PG-13 entices children to watch, but a program rated ‘sex, nudity, violence,’ does not. This kind of survey will give research a bad name,” Valenti said in a statement faxed to reporters Wednesday. Even though the cable industry financed the study, a spokesman for the NCTA declined to comment on the results.