Keira Knightley practices sex faces on Skype

Feb 2, 2012 at 8:25 p.m. ET

Keira Knightley practiced long and hard to get just the right facial expressions for her new movie -- but this role was a bit sexier than most. See why she had to work at it and why she almost didn't take the part.

Michael Fassbender, Keira Knightley, Viggo Mortenson

Getting into character for Keira Knightley's sexy new role in A Dangerous Method took the actress far outside of her comfort zone and straight into X-rated territory.

Knightley plays beautiful young psychiatric patient Sabina Spielrein, who gets off on being spanked. Since the actress claims this isn't in her usual bedroom repertoire, she had some practicing to do.

No, she didn't enlist someone to smack her bottom, at least not that she's admitting, but she did practice her O face both privately and for director David Cronenberg.

"It was a huge part of what Sabina was doing a lot of the time," Knightley told The Sun. "So I asked psychoanalysts about it and they said, 'Sex and anything like that is trying to release energy, trying to release pent-up emotion.'"

"So I worked with that and sat in my bathroom and pulled faces at myself for about two days, trying to figure out what it was going to be."

"Then I got on Skype with David and went, 'I've come up with this,' or, 'I've come up with this,' and he went, 'That one!'"

Poor guy's got a rough job.

In real life, Knightley's character had a sadomasochistic relationship with famed 20th century psychiatrist Carl Jung, regarded as the father of modern psychology. Michael Fassbender has the honor of spanking her in the flick.

But she almost didn't take the part because of the dark sex scenes.

"I went, 'I love you, I love it, but I really don't know if I want to do that. I'm really not sure about it,'" she recounted of a phone call she made to Cronenberg.

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"And he went, 'Well, I think it would be a tragedy if you didn't do the part because of that so if you want them out then we just won't shoot them or we'll find a way that will make you comfortable doing it.'"

"I realized they were integral to the piece, that it was really important to see them and show that within the study of that relationship," she said. That kind of made me go, 'Oh, OK, all right, as long as it's not some weird sort of sexy scene thing.'"

Watch Michael Fassbender spank the heck out of Keira Knightley when A Dangerous Method is released on Feb. 10, 2012. Just in time for Valentine's Day!

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