Britney Spears is not afraid to mix it up on The X Factor.
During auditions in Kansas City, Mo., with Simon Cowell out sick, his show's newest judge proved she is taking her job very seriously.
"She's got a really good instinct, and when she loves something, she looks like she wants to dance on the desk," a source says.
"When she doesn't like someone, she is incredibly tough."
Since joining X Factor last month, Spears, whose first week on the job was suspect, "she's really massively grown in confidence," a source says.
"She loves interesting and fun auditions and is prepared to stick her neck out and support someone no matter if some of the other judges disagree."
Her tough side came out this weekend, when she told one aspiring singer, "You have to be great to be on this show, so [I vote] no."
Ouch! During another audition, Spears, Demi Lovato, L.A. Reid and Cowell stand-in Louis Walsh ALL walked off the set of the show.
A young contestant who sang "And I Am Telling You I'm Not Going" from Dreamgirls told them that if she won, she'd use some of the $5-million prize to take care of her family, so they would never have to be homeless again.
"Whoa! I don't even believe you're real," Britney Spears, smiling, told the singer after a chills-inducing performance. "Was that just a track? You are amazing!"
"Holy cow! You are a little woman, and you're going to soar."
Time will tell if The X Factor will soar thanks to Spears.