Paul Dano discusses his new film Ruby Sparks

But they’re bundled together with hair that’s slicked back and blond, rectangular light-framed specs, a blue tailored jacket and pale-pink chinos. It’s more newly qualified architect than Hollywood actor. Then again, Dano appears in movies but he isn’t really Hollywood. It’s not just that he lives in New York (Brooklyn to be precise), or that after his highest profile role he took himself back to college for a full year, it’s in his demeanor.

Dano listens carefully and answers thoughtfully. He’s not worried about putting on a show, he’s more concerned about avoiding sounding self-important. Maybe it’s just his style. Maybe it’s the result of having been a jobbing actor for 16 years, despite only being 28.

Dano made his debut at 12 on Broadway, starring opposite George C Scott in Inherit the Wind. He said he started acting for a straightforward reason: “because I liked it”. In suburban Connecticut, where Dano grew up, after school activities were basketball and community theatre. Dano did both, but acting won out. It wasn’t ambition or the desire to be famous, he just liked acting. And he thought he might be able to be good at it.

Turns out he was right. Dano is a very fine actor. As the willfully mute older brother in Little Miss Sunshine, he brought a poignancy and pathos to teenage angst. As the pious preacher Paul Sunday (and his twin Eli) in Paul Thomas Anderson’s There Will Be Blood, he was scarily smooth and sanctimonious. Dano has built a film repertoire on playing awkward, alienated characters. In Ruby Sparks, his latest film, we get to see some of that, but then there’s also something completely, startlingly, wonderfully different.

Written by and co-starring Dano’s partner of five years, Zoe Kazan, Ruby Sparks is a quirky romantic comedy. Of course, that’s a term that has come to be used as a pejorative but in the case of this particular film that isn’t what I mean. This is a movie in which all convention is thrown out of the window, it’s smart and interesting and weird. But it’s also romantic and it will make you laugh, so rom-com it is.

Dano plays Calvin Weir-Fields, a writer who’s washed up after having written the great American novel as a precocious 18-year-old. He’s been spectacularly blocked ever since, spending his time rattling around in a minimal LA apartment as blank as the page in his typewriter, lost in existential angst about his writing, his lack of friends, his non-existent love life. There are trips to the gym with his bemused brother (Chris Messina), visits to his therapist, Dr Rosenthal (Elliott Gould) and futile attempts to bond with his dog.

In a last-gasp attempt to revive his failing creative spark, Calvin submits to an exercise given to him by his therapist. He is to write about his dog. In doing so he also writes about a girl – the eponymous Ruby Sparks. What he doesn’t expect is for Ruby to materialise, in his apartment, where she appears to live.

The character of Calvin is potentially tricky. Sometimes he’s pathetic, at other times he taps into darker issues of control and neediness when he starts “rewriting” Ruby, changing her to better suit what he thinks he wants. At moments it’s uncomfortable to watch, but of course, anyone who’s ever been in a relationship will experience a moment of thinking what life might be like if we could stop our other halves hogging the remote or slinging wet towels on the bed.

“I’m sure everybody would handle it differently but I felt it was a very human thing to go where it goes,” Dano says. “Dramatically, it’s the only way to fully explore the idea of controlling somebody. We’d be letting it off the hook if we didn’t. Once he makes that first mistake of changing her, the only place to go is where it goes.

“I empathised with Cal. He starts out in a tough spot and I think he just feels that life is out of control for him. That fear of life leads you sometimes to want to control it. I think he’s got some arrested development from being described as a genius having written the great American novel at 18. I don’t think he asked for any of that. I don’t think he’s that kind of guy.”

The part wasn’t exactly written for Dano, but not far off it. He read Kazan’s script soon after she’d started writing and long before she knew the twists and turns the story would take.

“The first lines that Ruby speaks I was like ‘yeah, only Zoe could do this’. Then I read Calvin and I asked her, are you writing this for us? I don’t think she knew that she was, but I think she was heading there.

“It was fun because I would come home and there might be something new to read or I’d at least see how it was going. It was something for us to daydream about together.”

Kazan knows one end of a script from another being the daughter of two screenwriters and the granddaughter of the legendary Elia Kazan as well as a respected actor in her own right. And Dano has garnered enough respect in his screen career to at least get people thinking, but he’s not known as a romantic lead so I wonder how likely he really thought it was that they could get the movie made?

“I think in almost a naive way I felt confident about it,” he says. “I don’t know why. I thought the script was good, but truthfully I also knew that she was my girlfriend and she was writing for us. Then we started sending it to people and they liked it a lot. That was a really good feeling and I’m sure even more so for Zoe.”

Dano says that Kazan was only ten or 15 pages into writing the screenplay when they both realised that the ideal people to direct the movie would be Jonathan Dayton and Valerie Faris, the husband and wife team who directed Little Miss Sunshine. It was, says Dano, something about “a sensibility, a tone” that made them think of the pair, whose first feature was nominated for four Academy Awards.

“We knew that we wanted it to be a romantic comedy of sorts and we were hoping that it could be fun and funny and magical and romantic. But we also knew that we wanted it to be something more than that and for it to have some depth or dark edges. They just intuitively felt like the right people.”

There can’t be many movies that are directed by a couple and which star a couple also playing a couple. Given that the film tackles some weighty emotional themes, I wonder if the shoot was fraught? Dano smiles. “I’d say it was a fun shoot. But I’d also say that the four of us cared greatly and definitely all pushed each other in some way. We had just enough time to make the film – it was a 30-day shoot which is fine but it was intense.”

Being in a relationship with Kazan informed the performance he says because they were able to draw on their history together – when they first met, their first kiss, what it was like to fall in love. As to whether there was an impact of being in a movie about a relationship while in a relationship, Dano isn’t that keen to explore that thought, at least not with me.

“A little bit,” he says, looking uncomfortable. “I hope Zoe would say the same thing but I feel like I almost take pride in what an individual person she is, it’s something that I really like about her so I hope that I don’t ever try to impose any idea of what she should be like on her. I think that’s one of the main things that the film deals with – that we have an idea of what somebody should be and we ask them to be that unfairly.”

As well as a study of what happens when we fall in love, the film is a rumination on fame and the weight of expectations. Set in the literary world it’s impossible to miss parallels with Hollywood. Calvin is feted and flattered and yet it does him no good. Dano must surely recognise the dangers of the young person thrust into the spotlight and then scrutinised relentlessly?

“I started young and I was always hyper aware of that to the point where I think after Little Miss Sunshine came out I went back to college for a full year.”

Dano says he recognises the situation of when everyone wants a piece of Calvin and how overwhelming that is.

“People all want something from him and they will be part of what determines success for him from now on. I think that’s probably the biggest struggle for anybody – not letting the externals overwhelm or matter too much.”

And yet, although that’s notoriously difficult in Dano’s business he appears to have managed to pick a path through it. I offer it more as a statement than a question, but I hope that Dano will answer.

He smiles. “We’ll see,” he says finally.

“I only know my own taste. If I read something and it inspires me in some way then that’s a good feeling. Sometimes you read things that you don’t get but another person might. Setting your own barometer for success is not easy to do. I don’t think I can do it but I’m trying to. There are lots of things I want to do. I’d be lying if I said I didn’t want to be successful or be a good actor but it’s more about learning about myself as I go.”

Hollywood isn’t exactly known for giving actors free rein. I hope that Ruby Sparks shows a different side of Dano that will lead to yet more varied projects, but I wonder whether he feels that he will be given the scope to do what he wants?

“I don’t know,” he says, frowning slightly. “I hope I will be. I’d happily go and make a film for $500,000. I’d happily make a film for $500 million. Just as long as I like the movie and I’m working with people I trust. The size and type of the film is less important. The script and the director is really what it’s about.” He pauses.

“I’d like to try to direct films at some point too. I will do that. I feel like I’m still at the beginning.”

Ruby Sparks (15) is on general release from Friday.