James Franco knew people would doubt Selena Gomez's acting talents when he cast her in his new movie In Dubious Battle.

The 24-year-old is best known for her singing career, but has acting credits to her name too. Her next role sees her star alongside Nat Wolff, Vincent D'Onofrio and James, in James’ latest directorial effort.

When it came to casting his movie, James understood people would be surprised by his choice of Selena, but he also predicted they would be blown away by her talents on screen.

"I think Selena is incredibly talented and I don't know what people think, but it seems to me she hasn't done tons of movies like this," he told Entertainment Tonight. "She even said that to me when I asked her to do this, she was like, 'Yes, I want to be a part of your world, I want to try it. I'm going to go on this adventure.'

"I felt like I had a secret weapon, that I knew she was a great actress, that people wouldn't be expecting her in this and that I could put her in this and she would nail it. And she did."

In the film, based on John Steinbeck's novel of the same name, Selena stars as Lisa London, a young woman in the 1930s labor movement who is coached through a grueling birth by James and Nat's characters.

Filming a birth scene would be a challenge for any young star who has yet to become a mother, but James insists Selena pulled it off with aplomb.

"She isn't a mother, right, but she did have those instincts," James continued. "She is like that, she is maternal in a lot of ways.

"It's a scene from the book and I just thought, if we do this scene, I know Selena is just going to give everything for it. And we did. It was almost like a piece of performance art or something like that, we had multiple cameras, we were in there and we just like kept it going. We had a real nurse, we had a real baby, all this stuff and we just kind of did it."