David Slade talks about Kristen's ability to be believable in her performances

" I know Kristen Stewart knocks herself out to be believable in her performances.

One of the things she said to me early on was, “If I don’t believe in it, I can’t do it. I’m a terrible liar, and if I don’t believe the words I say, then I can’t go through with saying them.” Sometimes it was tricky, massaging some of the line readings, but it was always in the process of getting it down. Kristen can be an exceptionally naturalistic actress in that way, but that’s really what I was looking for. We knew that this was the most mature of the books in how the story was told. It’s the conclusion of the love triangle, and a lot of the the themes in the first two books conclude in this book. We knew it would be a more adult and cinematic film, and we wanted to treat the drama as drama. There’s comedy, but the comedy is intentional."

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