LOS ANGELES (Reuters) - Britney Spears showed off her mean streak as the new talent judge on "The X Factor," but the TV singing contest stumbled with American viewers, drawing a smaller audience than last year and getting drowned out by "The Voice" and "America's Got Talent."
In a first head-to-head battle of three talent shows, an average 8.5 million Americans - about 3.5 million or 32 percent down from the 2011 opener - watched Spears and singer Demi Lovato make their debuts in the heavily-hyped two-hour season premiere of Fox show "The X Factor" on Wednesday.
Spears, the 30-year-old pop star who is reportedly being paid around $15 million a year, impressed critics and fans with cutting remarks and a no-nonsense dismissal of bad contestants vying for a $5 million prize and recording contract.
"I felt like I was listening to Alvin and the Chipmunks," she told one contestant. "I wanna know who let you onstage. I feel uncomfortable with you even staring at me," Spears told another.
Billboard.com's Marc Schneider said the "Toxic" singer "cast off her vacant-eyed reputation and showed herself to be a pro at delivering the kind of deliberate, tough-to-swallow feedback that often goes unsaid during these kinds of reality competitions."
But according to early Nielsen data, some 11 million tuned into the finale of "America's Got Talent" on NBC and 10.7 million watched a third episode this week of "The Voice", also on NBC, with celebrity music judges Christina Aguilera, Cee Lo Green, Blake Shelton and Adam Levine.
The competition was tougher in the 18-49 age group most prized by advertisers, with "X Factor" edging out a narrow win against "The Voice." NBC emerged as the most-watched U.S. network of Wednesday night and Fox was the overall winner in the 18-49 demographic.
"The Voice," the brightest light in struggling NBC's programming for several years, moved to a twice-a-year schedule this season in a closely watched decision.
NBC executives decided late last week to add a third night in the show's opening week, putting "The Voice" in direct competition for viewers with British entrepreneur Simon Cowell's revamped "The X Factor."
Cowell recruited Spears this year after he fired judges Paula Abdul and Nicole Scherzinger and host Steve Jones, following a disappointing first season.
Despite the slump in viewers, Spears and former Disney Channel star Lovato were a hit on social media. Social TV analytics firm Bluefin Labs said "X Factor" triggered about 1.4 million comments on Twitter, Facebook and other social media platforms on Wednesday, making it the most social season TV premiere of all time.
Lovato, 20, proved every bit Spears' equal in the popularity stakes, shedding tears over the tale of a 19-year-old contestant who broke down on stage when recalling how she, like Lovato, had been bullied at school.
Twitter hashtags #AwwwDemi and #DemiLovato were among the top trends on Twitter after the show on Wednesday.
"Pound-for-pound, Wednesday night's two-hour season two premiere of the 'X Factor' packed more emotional highs and lows into just two audition segments than most one-hour dramas manage in an entire episode," commented Gil Kaufman on MTV News.
Fox is a unit of News Corp and NBC is majority-owned by Comcast.
Reporting by Jill Serjeant; Editing by David Gregorio