In James Franco's new film, In Dubious Battle, Selena Gomez is the actor-director's "secret weapon."

Speaking to Entertainment Tonight on Wednesday (January 15), Franco spoke about casting Gomez as young mother Lisa London in his 1930s period film based on the John Steinbeck novel.

"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," Franco explained of Gomez, who he worked with on Spring Breakers in 2012. "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," he added.

In the movie, Gomez's character undergoes a brutal birthing scene—something Franco said came surprisingly natural for Gomez.

"She isn't a mother, right, but she did have those instincts," he explained. "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."

In Dubious Battle opens in theaters and on VOD February 17.

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