NEW YORK (CNN/Money) - Sex and violence don't necessarily sell, according to a University of Michigan professor who says studies show that viewers remember the commercials on more racy programs far less often then they do on more neutral fare.

A University of Michigan professor says viewers remember far fewer advertisers on shows with sex or violence, like 'NYPD Blue,' than on less racy shows.

Brad Bushman, a professor of psychology and communications studies, says that studies he has conducted show that viewers who watch relatively inoffensive shows, like home improvement show "Trading Spaces" or "America's Funniest Animals," remember about 20 percent more advertisers they saw on the shows than they do on shows like "The Man Show," "Cops," or "NYPD Blue," which carry "S" and/or "V" warnings for sexual or violent content.

Bushman says that one of the studies he conducted was funded by television networks NBC and PAX; the latter doesn't carry shows with sex or violence warnings. Another was paid for by a grant from Iowa State University, where he taught until this coming school year, and where he conducted the research.

"We know that violence and sex grab our attention. It may be they divert the attention away from the advertising messages," he said. "We're doing more research into the reasons behind the finding."

One of the studies was published in the Journal of Applied Psychology; another is soon to be published. He said that he has not received any support from groups pushing for less sex and violence on television and that he would have published the results if he had found the opposite to be true.

Bushman inserted the same selection of advertisements in all the different types of programs, and then asked more than 300 subjects to watch the shows in a controlled environment.

They were told they would be asked questions about their opinions on the shows, but they were not warned they would be asked to remember the advertisers. They were then quizzed about their recall of the ads 15 to 20 minutes after watching the shows and the next day.

Network spokesmen were not immediately available for comment on the study. Independent media analyst Jack Myers, editor of The Jack Myers Report, said he has not seen Bushman's study, but it seems to contradict industry studies that show basically the same advertising retention for both racy and non-racy shows. He said advertisers usually are wary of sex and violence, at least when a program first airs.

"Shows like 'NYPD Blue' when it came on air, it was being discounted (by advertisers)," Myers said. "Once the audience shows loyalty to a show, advertisers pay a premium, not to be associated with sex and violence, but to reach those loyal viewers."

He said that he doubts that Bushman's study will scare advertisers away from shows with the "S" or "V" warning labels.

"Advertisers in general are very sensitive to content issues. They watch every episode of questionable shows and make decisions carefully," said Myers. "This study will not change their current approach, in my opinion."

Bushman said he's already been contacted by the president of one major food maker asking for copies of his study, and expressing concern about his commercials not being remembered by viewers. But even if his findings are widely accepted, he doesn't expect violence and sex to disappear from the airways.

"Violent and sexually explicit programs might still be attractive – they tend to draw 18- to 34-year-old viewers and that's the age group they (advertisers) are interested in reaching," Bushman said. "Their attitudes (about products) are less set and they have more disposable income."