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RD / Johnson / Retna Digital 1 / 9

Why does Victoria Beckham rarely smile?

"I do have my insecurities," Posh Spice, 35, tells October's Elle. "Maybe that's why I look a little bit serious. The kind of person who's going to stand on the red carpet and have the big grin — I'm not like that. I want to get in there, do what I've got to do, and get home to my kids."

Beckham recently served as a guest judge on the upcoming season Fox's American Idol.

But don't expect to see her on the small screen often.

She calls reports that she wants an acting career "rubbish."

Says Beckham (who has her own fashion line, DVB by Victoria Beckham): "I know my boundaries — I know what I am good at and what I'm not good at."

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