There's a lovely informality to the New York press day for The Host, the highly anticipated new sci-fi thriller starring Ireland’s Saoirse Ronan, 18, which might have something to do with the nationality of the young star. 

Charismatic and funny, she’s Ireland’s idea of a movie star, which means she’s prodigiously talented and world famous, but she’s still completely approachable. Only one country in the world could combine those two qualities so successfully, probably.

Racing through the hallways of the Crosby Hotel in upscale Soho on Tuesday, Ronan’s an on point professional, but she’s also just 18. So she’s smart to give room to both sides of her life and career, as she grows up as the foremost young actress of her generation (a description that would make her laugh, but is nonetheless true). 

Ronan’s been promoting The Host (the film opens nationwide this Friday, 29) for weeks now, and this is her last but one press day in New York before the Easter holidays. That means this weekend she’ll be fighting aliens, saving the world and will still be back home in Co. Carlow for her Easter dinner.  

But is Ronan, already an Oscar nominee at the tender age of 12 thanks to her 2007 breakout role in Atonement, ready for the whole new level of fame that comes with starring in a Stephenie Meyer film?

“It’s mad because I just don’t really think about that kind of stuff,” she tells the Irish Voice. 

“It’s not even that I take a decision not to think about it, I just can’t. I don’t think that’s going to happen. So far the films I have made have been indie films that just happened to do well. Even with something like Hanna, we didn’t think that would do great and it did, people really liked it. This is the first time where there has been so much tension around it and so much hype.”

There’s no question that starring in the massively successful Twilight films, based on Meyer’s books, changed the lives of the two stars Robert Pattinson and Kristen Stewart -- often for the worse -- but it’s impossible to imagine Ronan, a precocious and clearly well adjusted young woman morphing into another Lindsay Lohan five alarm car crash.

“It’s a different audience, and I’ve never done a film for that kind of audience before,” Ronan admits, but she sees the positive side. “They are more fanatical fans about the stuff that they’re interested in because they’re younger, they’re kids! It’s been fine so far. I’m hoping it won’t be something that blows up too much for me in that way.”

The premise of The Host is simple. Alien invaders called the Souls arrive and colonize the planet by taking over the bodies of their human hosts. 

When the film opens most people in the world have already been converted, resulting in the “death” of their human personalities but not their bodies. 

It’s an eerie premise, and the film does a terrific job of portraying how creepy the world looks after the invasion nears completion. But there is one powerful force on earth the aliens have never encountered before, and don’t know how to contend with -- human love. 

From the get go young Melanie Stryder (Ronan) gives these aliens a serious run for their money. Although she’s quickly captured and turned into another host carrier, she still refuses to have her mind erased and instead risks everything to protect the people she loves. In the role Ronan gives a sensational performance that carries the film throughout.

As an Irish person, does the idea that you could have your capacity for passion and argument removed hold a particular terror, I ask her? 

“That’s an interesting question. I have to say I did find it more of a challenge playing Wanda (the short name for Wanderer, the alien character that inhabits Ronan’s body) I think because there’s so many situations she’s in where you would naturally freak out or have the human impulse to scream or to cry or get angry and really let your emotions out like we, the Irish do. But at the same time we do suppress a lot of emotions!”

For Ronan the decision to play the lead role in The Host was the obvious acting challenge of playing two people forced to share the same body. It’s a nightmare situation, but it’s also completely compelling. 

Who will be top dog? Who will call the shots? Can two completely different personalities make peace with each other in the one body? 

“It was really the main draw for me that I would get to play two characters in the one person. And that’s the way I looked at it. It’s two separate women, and just because physically you don’t see one of them for the majority of the film doesn’t mean they’re not there. I really enjoyed doing that,” she says.

Ronan is holding up really well considering this is her second week of promotion for the film. What’s it been like, I ask her? 

“They keep asking me about kissing boys all the time. Like, ‘Oh it must be so difficult for you to be kissing two boys in the one film,’ and I’m saying, I really don’t care.”

That Irish directness undercuts all the Hollywood starlet nonsense that surrounds her. It’ll protect her from most of the nonsense that accompanies being a star at her level now. 

And as she’s growing up quickly it has become time to explore more romantic roles -- but Saoirse Ronan-style romantic roles, which mean strong and independent and fiercely proud.

“There’s a lot of pushing and pulling in this film and I think that’s something you get in every relationship you have with another person. I had never gotten to play a role like that before, where the romance was such a focus in the story,” she says.

At 18, isn’t it the perfect time to explore romantic roles, I ask her? 

“I had done romantic scenes but for the story to be so much about love. Then the film I did straight after, How I Live Now, was also very much about love. It was the right time for that to happen. Maturity wise I think it was the right time for that to happen too.”

Ronan is currently filming The Grand Budapest Hotel with director Wes Anderson. The cast is a who’s who of Hollywood royalty, including Bill Murray, Ralph Fiennes, Willem Dafoe, Tilda Swinton, Jude Law, Edward Norton and Owen Wilson. It’s heady company for the young actress but, as they say in Carlow, there’s not a bother on her. 

In fact, for the first time ever she’ll be playing a role in her own Carlow accent. “I didn’t know that was going to be the case,” reveals Ronan. “Wes Anderson and I were just talking about it one day. It was actually my very first meeting with him. 

“I only have a few scenes where there’s dialogue. Everyone has a couple of main scenes in the film. And we were chatting away and I asked, ‘Listen, what sort of an accent do you want me to do for it?’”

Anderson is great because he’s very open to changes, Ronan says. 

“He has a very clear idea of what he wants but he’s also so relaxed about everything. At the drop of a hat he decided, ‘Okay, let’s use your Irish accent.’ I had never used it before and I think he said yes because I had never done it before. 

Ronan is well aware that she could lose half the America audience. 

“He said, ‘Read the scene in your Irish accent.’ I did, then he said, ‘Make it slightly milder,’ because as you can hear I have quite a strong one. We just stuck to that. Everyone in the film is from different places and it’s set in a hotel. Tilda (Swinton) is English and Ralph (Fiennes) is English and I’m the Irish one.”

It’s almost Easter, which means The Host opens the same weekend she gets a little time off after months of non-stop filming. She’s beaming at the thought of a dinner with friends and family in Ireland on Sunday.

“Just to be home,” Ronan sighs. “I mean, I haven’t talked to my mam properly in a few months and I really miss her. We get home to Carlow on Saturday and I’m really looking forward to Easter Sunday dinner and having lamb and being with my dog and going for a walk by the sea! 

“I’m really looking forward to that. It’s a good reality check to go home and be with the people I love.”

Watch the trailer for 'The Host' here: