Britney Spears and a number of other pop stars are in their 20s now, eager to shed their adolescent image, and apparently more of their clothes, in an effort to show the world they are adults.

Spears, Christina Aguilera, LeAnn Rimes and Justin Timberlake are among those entering the "next phase" of their careers -- the time to ditch the teenyboppers and shoot for a more mature audience.

But will it work?

A sexy image is a simple-minded way to show you're an adult, according to Stuart Fischoff, professor of media psychology at California State University in Los Angeles.

"How do I prove that I'm adult? I’ll show breast rather than showing intellectual signs of maturity," he said. "If we equate adult with sexuality -- as our society does -- one of the quickest ways to shatter an image of being a child ... is by getting nude, or scanty."

Just a few years ago, a teenager's bare belly button could cause a commotion. But that all seems tame today, compared with Aguilera's aptly named "Dirrty," or Spears' simulated orgy in the "Slave 4 U" video.

"If you want to be successful right now in the adult market you have to be sexy," said Atoosa Rubenstein, editor of Cosmo Girl.

Country crooner Rimes rode to fame at 14 with a song about being blue, but has va-va-voomed to appearing in an over-the-shoulder topless shot on the cover of Blender this month.

And upping the sex appeal isn't reserved for the post-teen set.

Sheryl Crow, 40, and Faith Hill, 35, have both recently turned up the heat to get fans in their kitchen. Hill appears in her latest video glistening wet, clothes matted to her body, while Crow showed off her toned body in hot pants on the cover of lad mag Stuff.

And the transitions aren't just happening among women. Justin Timberlake ('N Sync) and Nick Carter (Backstreet Boys) each recently released solo albums and are trying to shed the sweet for sultry.

"Fourteen-year-olds are over Justin, but women in their 20s now think he's hot," said Rubenstein.

But the shift to dominatrix-style duds and bluntly sexual lyrics are turning off some teens.

"As Britney has changed her image, there is a direct correlation with her drop in popularity," said Rubenstein. "Aguilera's new video is one step away from pornography. Teenage fans feel alienated by the new image -- they can't bring it home."

The MTV.com message boards reflect that distaste for the young divas. "I have always thought Christina Aguilera was talented — she has such a great voice — but is it necessary for all female pop divas to go through this slutty stage of their careers?" asked Melissa, of Clinton Park, N.Y.

"I think Britney's total conversion from innocent, virginal schoolgirl to snake-toting 'slave' for you was shocking for most teens," said Dodai Stewart, senior editor for J-14 , an entertainment magazine for teens. "As for Christina, she never claimed to be a virgin!"

Aguilera apparently looks at it as growing up, and gaining independence. "Now people are going to get to see the real me," she said about her new album, Stripped, in an April Allure interview. "I'm growing up," she said, explaining that her record label in the early '90s monitored her look. "Everybody wanted their all-American girl," she said. "Maybe that's why I'm rebelling!"

But these so-called signs of independence and maturity are really just as closely controlled as before, said Rubenstein.

"When they were successful with teenagers what they sang about was love they couldn't catch … now it's about sex," she said. "They have to have some reason for making such a shift and the reality is it's marketing to tap into an adult audience. If you're an act for adults you can go on forever. They want to have long careers."

Teens now favor a new crop of female stars christened the "anti-Britneys" including Pink, Avril Lavigne and Michelle Branch.

But Spears' manager already has an idea of how to best reincarnate the star: The New York Times recently reported he said she might take a more overtly sexual approach.

"They are just following a system that works," said Rubenstein. "Take it off and make money."