Natalie grows up

It's been a decade now since a 12-year-old Natalie Portman made her screen debut in

Today, at the age of 23, Portman still has the same disconcerting effect - in reverse. Now it is the childlike innocence with which she invests her adult characters that lends her acting its greatest appeal. 'I think that everyone has a combination (of child and adult) and the reason they always make precocious children in film is because we all have this love of purity, the untainted quality of children,' she says, with all the wisdom of a woman who has just obtained a psychology degree from Harvard University. 'Children seem to have this intuitive knowledge and joy with the world, which seems to get damaged as you get more experience with age. And it seems as if you lose that knowledge almost, and you become stupider as you get older instead of actually gaining wisdom from your experience.'

Yet Portman seems to have become smarter as she has grown up. By the time she left school she had worked with some of the most acclaimed film-makers of our time: Woody Allen (Everyone Says I Love You), Michael Mann (Heat), Tim Burton (Mars Attacks!) and, most notably, George Lucas, playing Queen Amidala in the three Star Wars prequels. Like Foster and Shields, who studied at Yale and Princeton respectively, she attended Ivy League university.

A similar sense of responsibility has informed her work, too: at 16 she rejected British director Adrian Lyne's offer to star in his 1997 remake of Lolita. 'I don't think there needs to be a movie out there where a child has sex with an adult,' she said, with admirable precocity. Of her next big opportunity, with Ang Lee, she explained, 'I was going to do The Ice Storm but they wouldn't change some of the sexuality in it.' Later she turned down The Horse Whisperer, choosing instead to make her Broadway stage debut in The Diary Of Anne Frank, augmenting her growing reputation as a serious adult actress.

Her next two roles will surely draw a line under the child-star image. In Zach Braff's quirky small-town rom-com Garden State, which is being hailed by critics as The Graduate of its generation, she's a charmingly unconventional leading lady. It's a thoroughly engaging performance as a character with brains, beauty and offbeat humour - perhaps not the biggest stretch for Portman, who exhibits all those qualities in the flesh, along with a tendency to be earnest when talking about herself.

Her father, Avner, an Israeli fertility doctor, and artist mother Shelley, from Ohio, moved to the USA when Jerusalem-born Natalie was three. Since then she has been outspoken on a number of pro-Israeli and liberal causes, most recently campaigning for John Kerry and working for a micro-finance organisation called Finca, which gives loans to women in developing nations. It's a role that has taken her to Uganda and Guatemala, and about which she talks with knowledge and passion.

'There are women my age with 10 kids on a dollar a day, with inadequate food and water and medicine, and everyone is dying of Aids and malaria. Many of these women are illiterate and have to sign their loan cheques with a fingerprint and yet they are running successful businesses, paying their loans back on time and sending their kids to university from the money they make from their businesses. It's humbling.'

In her personal life, about which she steadfastly refuses to talk,

Christensen, Lukas Haas, Jake Gyllenhaal and Gael Garc"a Bernal, as well as the musician Moby. She is currently reported to be involved with Braff, who wrote, directed and starred in Garden State and somehow persuaded a stockbroker friend to put up its entire $2.5 million budget - and Portman totake a massive pay cut from Star Wars for his debut.

Any lingering vestiges of Portman's juvenile persona will be erased when she is seen next year as a lapdancer in an eagerly anticipated adaptation of Patrick Marber's incisive drama of sexual mores, Closer, alongside Julia Roberts, Jude Lawand Clive Owen. Characteristically, she later persuaded director Mike Nichols - a mentor since she appeared in his 2001 stage production of The Seagull - to leave her nude scenes on the cutting-room floor. 'It's amazing how the film shocks with just its language,' she enthuses. 'There's no sex or violence in the movie and yet it's more shocking than anything.'

Much has been made of Portman's skillful avoidance of sexually explicit roles, but she laughs off any idea that she's a prude. 'People make a big issue out of it but I've only recently been legal,' she laughs. 'Obviously when you're 14 or 15 you're not really wanting to do sexual things on screen when you haven't even got an idea of your own sexual identity.' She says she recently watched Léon again to record a commentary for a 10th-anniversary DVD, seeing it through adult eyes. But she says its sexual undertones came as no surprise. 'I think I was pretty aware of my sexuality at the time. I was very aware of my girlish powers,' she says. 'And yeah, there are undertones. But it never crosses the line into exploitation, I don't think.'

In person, Portman displays the same confusion of girlish enthusiasm and adult caution that she brings to her roles. 'I'm sort of wary of people,' she confesses, 'because in our society celebrity has become such a widespread and empty phenomenon that people come up to me all the time who probably couldn't care less.' She confesses that she's just as bad herself, as easily impressed when a celebrity enters the room as the next tabloid reader, but I don't believe her for a minute. Far easier to believe this archetypal 'old soul in a young body' when she says: 'I've never had a rebellious phase,' and adds, 'I don't think I ever will. I just feel I want to be guided more by myself than by what anyone else says, or what anyone else thinks I should be.' On the evidence so far, she seems to be doing a pretty good job.