Sitting on a stripy sofa in an open-air restaurant, her publicist has wafted a menu in front of her. "I was starting to get that spacey, 'seeing spots' thing," she says. "All you can do, if you have an interview and you're hungry, is think about when you're going to eat." In a world where A-List actresses survive on celery sticks, it's the sort of comment that makes you warm to this vivacious 29-year-old.
Esquire magazine may have twice dubbed her the Sexiest Woman Alive, but Johansson doesn't play up to such hype. Today, she's dressed in a navy trouser suit; her chunky brown heels have been casually discarded on the floor, allowing her to tuck her bare feet underneath her legs and curl up on the sofa. Like her photo-shoot in the current Vanity Fair issue - all natural, no make-up - it's a pose that suggests how laid back she can be.
Put that down to the fact she still lives in her native New York, rather than in the belly of Hollywood, quashing any inflated sense of self-importance. Take her recent ego-popping trip to the airport when she was accosted by an autograph hunter. "They said 'My daughter is your biggest fan. She loves your work. You are Taylor Swift, right?'" Never mind that the songstress is taller and younger than Johansson, she took it in good spirits. "I wrote to my friend and said 'How should I feel about this?' He wrote back 'Appalled, thrilled and don't think about it too much.'"
Johansson may not have matched Swift in sales, but she has put that husky voice of hers to impressive use (and not just as the seductive computer in Spike Jonze's recent Her). In 2007, she sang backing vocals on a performance of Just Like Honey with the Jesus and Mary Chain at the Coachella festival in California; then, a year later, she recorded an album of Tom Waits covers, Anywhere I Lay My Head (the NME praised its "ghostly magic"). "I can't imagine that being my full-time career," she says, though recently, she cut a duet disc with Pete Yorn, based on Serge Gainsbourg's collaborations with Brigitte Bardot.
It's been a decade since we first met, just a few hundred yards from where we are now, when Johansson arrived at the Venice Film Festival to present Lost In Translation. Back then, while she'd appeared in films like Ghost World and The Man Who Wasn't There, she was relatively unknown. But appearing in Sofia Coppola's delicate Tokyo-set tale as the aimless girl who enjoys a "moment" with Bill Murray's washed-up actor sent her into orbit. "I had no idea people would respond in the way they did," she says.
She's been back here since - for A Love Song For Bobby Long and The Black Dahlia - during which time she's become one of the most in-demand actresses of her generation. So today, 10 years on, she's in reflective mood. "It's good to take the time to recognise that I did put in a lot of work," she nods. "And recognise the chances you take, the risks you take, and what works and what doesn't, and how you've grown as an actor."
Certainly, there have been flops - the Michael Bay disaster The Island, for example - but more often than not Johansson has made canny critical or commercial choices. She's worked with Woody Allen three times - including acclaimed performances in Match Point and Vicky Cristina Barcelona. And, doubtless to her agents' delight, she's the ultra-limber Marvel Comics hero Black Widow in Iron Man 2, The Avengers and next month's Captain America: The Winter Soldier.
Yet nothing Johansson has done quite matches up to her latest movie, Under The Skin - the reason she's back in Venice. "Bringing this film here feels like you're tying a ribbon in a way," she says. "It's a nice cherry on the cake." Well that's one way of describing arguably her riskiest film so far - a daring, unorthodox new work from Sexy Beast director Jonathan Glazer.
"More and more, I'm accepting that life is a risk and sometimes it works and sometimes it doesn't," she counters. "You never know unless you take the risk. I was thinking earlier, it would probably be riskier if I did a film that was really generic and it didn't work. That would probably be worse. With this film, it's not really risky because you have nothing to lose - as you don't know what you have to gain, exactly. Whereas a film that's a generic popcorn blockbuster, if that's a bomb, then it's a commercial failure."
Loosely based on the 2001 sci-fi novel by Michel Faber, Under The Skin sees her play an extraterrestrial being - nominally named Laura - adrift in Scotland. It was filmed mostly around Glasgow - with some scenes in Glencoe - and she was on location in such glamorous locations as Wishaw, Newmains, Govan and Port Glasgow.
With minimal dialogue, she trawls the landscape in a white van, picking up young men and then luring them to their doom. In the book, she's capturing earthlings to send back to her planet, where human flesh is seen as a delicacy. But there is no such explanation here, Glazer paring down the script to create a beguiling, sensory experience.
Destined to polarise viewers ("a movie like this is never going to be the movie you watch over Thanksgiving," she says), the result is an overwhelming, intoxicating, almost suffocating film, as Johansson experienced when she first saw it. "I felt really anxious," she admits. "It was strange. I remember I watched it with my assistant, who was with me for some of the filming, and the two of us left the theatre and she was like 'I can't breathe! I need to do some stretches or something.' It was funny. It's very disorientating."
Aptly enough, Under The Skin closes Glasgow Film Festival in just over a week before it goes on general release. "Scotland's so incredibly special," she says. "I'd never been there before. Obviously, it's so pristine and gorgeous….I like Glasgow, though, I have to say. I really enjoyed that city. I like it. I think it's akin to New York in a sense. There are a lot of young people there. Our crew could really party hard, as you could imagine. Sometimes you needed that after an impossible day. But I'm pretty fastidious when I'm working. I'm pretty focused."
What about local delicacies? Did she sample some famous Scottish cuisine? "I don't eat red meat, so I did try the vegetarian haggis. It tasted like stuffing," she laughs. "And Irn-Bru - that's got a kick. You put in enough vodka, it'll be OK."
What about trying deep-fried Mars bars? "I wish I had," she sighs. "I don't know why I found out about those after the fact. I come from the land of deep-fried everything." But would she really want to eat chocolate and batter? "It sounds good to me. I'm a girl - we like everything like that."
With a number of nude scenes to contend with, it's probably just as well she didn't gorge on fatty foods. While she once posed naked (very tastefully) for the cover of Vanity Fair - she and Kiera Knightley elegantly arranged next to fashion designer Tom Ford - Johansson is almost surprised when I ask if she ever has body issues. "Erm … yeah, I mean, I'm human!" she blurts. "Yeah of course - I'm a girl! You wake up every day and go 'Oh, what changed while I slept?'"
If the film primarily meditates on loneliness and being "alien", then Johansson says she can relate.
"Just the fact I'm publicly recognised can be very isolating, alienating," she says. "I think a lot of people look at a recognisable person and they put their own emotions onto it. What they don't think about is the actual person; it's hard to humanise when you have this glamorous idea of someone. It makes them almost inhuman. But as I've gotten older, I've learned more to be able to be with myself. I feel more in my own skin."
Talking of ageing, her next "milestone", as she puts it, will be her 30th birthday this November. "I guess that's a big one," she shrugs. Has she set herself goals to achieve by then? "Oh God, no, but I've never been like that, though. Never. That's also because I've experienced a lot early on and I didn't have those same goals that maybe somebody just starting out in college might have. For me it started at such a young age … I learned to not expect anything."
Given she was named after Gone With The Wind's heroine Scarlett O'Hara, Johansson seemed pre-destined for the big screen. "When I was little, I was a singing, dancing kid," she notes. "I took all kinds of classes. I was one of those jazz-hands kids." She began in commercials, after a family friend suggested her mother take her and her three siblings to an agency. "The only person they wanted was my older brother, Adrian. I was totally devastated. I still can't sell anything - I'm terrible at it!"
It only made her more determined. "Whether it was the rejection or some calling, I wanted to try," she says. Still, this ambition left her parents hesitant. "My mom never really wanted me to get into acting because she was afraid it would be very competitive and stressful - which it is." Tellingly, she was never home-tutored, her parents making sure she attended regular schools. "When kids were outside playing, it wasn't as if I couldn't join them because I had an audition. I had a pretty normal life - I just had this added bonus of being able to do what I love to do."
By the age of 10, she'd made her film debut in Rob Reiner's 1994 comedy North. A year later, she was playing Sean Connery's daughter in Just Cause. By the time Robert Redford picked her for a show-stopping part in his 1998 Nicholas Sparks adaptation The Horse Whisperer, she already had a body of work behind her - despite being billed in the credits with the rather insulting 'Introducing Scarlett Johansson'. "I was pretty pissed off about it," she reflects. "I was like: 'Screw them!' It was bizarre."
It was around this time that her mother separated from her father, a Manhattan architect of Danish extraction. But Johansson maintains that life was never fraught; even now, her career does not impinge upon family time. "I don't even know if they've seen a lot of my movies. I very rarely talk about work with my family, and I think that's a side effect of the fact I started so young."
She's far more likely to talk about politics with them than anything else. "I grew up in a politically verbal family," she says. "I went with my mom to mayoral rallies and I went with her to vote. We used to watch the debates. My brother Hunter ended up working in local politics, so it's always something I've been aware of."
In the past, she's campaigned for John Kerry and President Obama, and recently backed Hillary Clinton.
Johansson gives off the impression that she's more than capable of handling herself in a political argument. She severed ties with the humanitarian charity Oxfam International after eight years as a global ambassador. It came over what was called "a fundamental difference of opinion" over her endorsement work with SodaStream, the soft drinks company that owns a factory in the Israeli settlement in the West Bank.
In a statement, Oxfam reiterated its position, that it opposed all trade from Israeli settlements in Palestinian territories, partly because businesses such as Soda Stream "further the ongoing poverty and denial of rights of the Palestinian communities". Johansson, who has endorsed numerous high-end brands, including Dolce & Gabbana and L'Oreal, hit back, noting that she was a "supporter of economic cooperation and social interaction between a democratic Israel and Palestine." How this will affect her public image is anyone's guess.
For the most part, the press has focused on her string of high-profile relationships - including actors Josh Hartnett, Sean Penn and, of course, Ryan Reynolds, whom she married in 2008.
"I dated actors for such a long time," she tells me. "Actors date actors. It makes sense. You have the same schedule, you have the same vocabulary."
But after her marriage to Reynolds collapsed in 2011, Johansson took a step away from Hollywood folk. She's now engaged to advertising executive Romain Dauriac. "We met through mutual friends," she explains. Initially, it was tough, though. "I was so used to being in a relationship with an actor where it had to be hush-hush or hidden from the press. It adds this importance to a relationship early on that doesn't need to be there. So meeting somebody who was in a completely different field … it was such a different thing."
Being tracked by photographers - "the 'citizen paparazzi' I call them" - doesn't stop her day-to-day, though. "I go out all the time. I know New York like the back of my hand. I refuse to be a prisoner." It helps that there's not the focus on celebrity there that you find in LA, keeping that ego healthily in check. "New York doesn't give a s***."
In the coming months, she can be seen in foodie-themed family drama Chef, which reunites her with her Iron Man 2 director Jon Favreau and its star Robert Downey Jr. Marvel fans won't have to wait that long, with Johansson's Black Widow appearing in Captain America: The Winter Soldier - or "Cap 2" as she calls it - in March, yet another piece in the jigsaw before next summer's Avengers: Age Of Ultron - the sequel to Joss Whedon's superhero ensemble, The Avengers.
If rumours are to be believed, Johansson will become one of the highest-paid actresses ever after making what will be her fourth appearance as Black Widow. But it seems unlikely that Johansson will warp into some kind of monstrous diva. She's survived this far.
THE FILMING PROCESS
The adaption of Michel Faber's novel of the same name was mostly filmed in and around Glasgow. Glazer, best known for Sexy Beast, filmed the movie to mirror Scarlett Johansson's character, an alien who preys on unsuspecting men.
During filming, passers by were approached by Johansson, who drove around Glasgow in a van and asked them to get inside with her. Distant camera crews and hidden cameras were used to capture their reactions. Despite her Hollywood fame and being voted Esquire's world's sexiest woman twice, most of the men approached by Johansson did not recognise her. Only after they had been filmed were the men asked if they objected to being in the movie.
In the film's two-minute trailer she is shown asking one of her victims: "Do you think I'm pretty?"
In Under the Skin, it is not Johansson that looks alien but the smoking, drinking Glaswegians. In fact, Glazer portrays the city and
its inhabitants as a disturbing and confusing species.
After its premiere at the Venice film festival the crowd started to boo the film. Glazer has said: "I was at that screening and I thought that sound was great. The booing and clapping combination is, to my ear, a phenominal sound. I'll never forget it."
The film did, however, recieve a positive review from seven out of 10 critics on RottenTomatoes.com.
The reaction of the Scottish audience will be one to watch as the film does not show Glasgow or its surroundings in a particularly good light. Quite the opposite.
It will be interesting to see their reactions.
Under The Skin (15) screens at the Glasgow Film Festival on March 2 at 8pm and goes on general release on March 14. Captain America: The Winter Soldier (tbc) opens on March 28.