Since first gaining attention for his powerful — and frightening — turn as a murderous bigot in Boys Don't Cry, Peter Sarsgaard has repeatedly proven he's unafraid of challenging roles.

A computer genius who spends three days exploring the boundaries of sexual desire with a Vegas lap dancer? Check. He did that in The Center of the World, back in 2001. A quiet magazine editor who discovers his top writer is a fraudulent hack? See his critically acclaimed turn in last year's Shattered Glass.

Next up, in Kinsey (opening Friday), Sarsgaard ventures where few young actors dare to tread: the full-frontal nude scene. Asked if he was nervous about doing the full monty, the 33-year-old actor just smiles serenely.

"It didn't feel like anything," he says. "I mean, if I always thought about the people on the other end of the camera — as if it were like a tube going to audiences all over the world — then I wouldn't be able to act anyway. This was just a room filled with four people and it seemed appropriate for the scene. The reason I'm nude is to test the waters before I [kiss Dr. Kinsey] later in the scene. It had a purpose. It's not nudity for you guys, it's nudity for him."

Sarsgaard plays Clyde Martin, a young assistant to the controversial sexpert Alfred Kinsey (Liam Neeson). Though their relationship is strictly professional at first, both men soon realize they're interested in getting to know each other on a more intimate level. "I think it had something to do with his charisma, certainly," remarks Sarsgaard about Clyde's attraction to Kinsey. "I think Kinsey was exploring something in Clyde, and Clyde sees something in him. It's not about the research, it's about this man's ambition and drive, and that's attractive."

Earlier this year, Sarsgaard turned in another memorable performance as an eccentric slacker in Garden State. The actor admits he's surprised by the indie movie's popularity, but says he never thought of Scrubs star Zach Braff's first big-screen venture as a risky proposition.

"The only movies that are a risk to me are those that are going to be seen no matter what," he says. "You do a big-budget movie and the studio will market the hell out of it [regardless]. Garden State was made for very little money and if it had been bad, it wouldn't have gotten into Sundance and no one would have seen it. I really liked my character in that film. I'm never asked to do comedy in movies, even though I think I'm pretty funny!"