Miley Cyrus: 'Justin Bieber acts like he is 12'

Miley Cyrus is convinced troubled pop star Justin Bieber is struggling with fame because he has failed to grow up emotionally and still acts like he is 12 years old.

Cyrus, 20, admits she hangs out with Bieber, 19, a "little bit" and has been attempting to help him get his life back on track following a series of headline-grabbing stunts, including an Internet video which showed him urinating into a restaurant mop bucket, nightclub fights and brushes with the police.

The former Hannah Montana star is convinced fame has stunted Bieber's emotional growth, and he is rebelling because he doesn't know any better.

She tells Rolling Stone magazine, "(I hang out with him) a little bit. But not really. I'm not much older than him, so I never want it to feel like I'm mentoring him. But I do mentor him in a way... I just don't want to see him (mess) that (his career) up, to where people think he's Vanilla Ice. I tell him that. Like, 'You don't want to become a joke. When you go out, don't start (fights). Don't come in shirtless.' But the thing is. I think boys are, like, seven years behind. So in his head, he's really, like, 12."

However, Cyrus is adamant the young star really is talented, adding, "He's trying really hard. People don't take him seriously, but he really can play the drums, he really can play guitar, he really can sing."