By Sona Charaipotra
Updated November 12, 2004 06:00 AM

Even when the cameras were off, says Kinsey star Peter Sarsgaard, we “were talking about sex all the time.” The 33-year-old actor, who plays researcher Clyde Martin in the film about Alfred Kinsey’s 1940s sex studies, recently shared his own thoughts on the birds and the bees – including what it was like filming a kiss with costar Liam Neeson.

How did you first learn about the facts of life?
Probably (from) priests, mostly. I had to take a course on relationships in (a Jesuit) high school, which was their way of teaching us about that stuff. We watched Ordinary People. It was always underhand.

Why this movie now?
I just thought the topic was timeless. I mean, this country seems like it’s always wrestling with sexual issues – gay marriage issue, for instance.

How do you think the heartland will take to the film?
I actually think it’ll play quite well where I’m from, which is St. Louis. I could picture it playing well in Oklahoma. I think a lot of the humor in the movie depends on you being a little bit squeamish or titillated by sex. The tighter you are going in, the more you’ll laugh. If you’re, you know, somebody who’s into swinging and free love, I doubt you’d find a lot of it funny.

What was it like on the set?
We all, obviously, were talking about sex all the time while we weren’t filming. I love that question, “When did your parents’ home stop feeling like your own home?” And we would ask each other questions like that, some of the more interesting ones.

So, when did your parents’ home stop feeling like your own?
Seven. (Laughs)

And how was it working with Liam Neeson?
The relationship of young actor to big famous movie star sort of fits in this movie. It’s like I want a piece of what’s going on in Liam’s head. That probably shows up in the movie, just the way I look at him, the respect I give him.

You two share a kiss. Was it good, and how was it to film?
Short answer to that is no. … (But) the only reason you have to be afraid, I guess, is that you might be turned on. That would be the most embarrassing thing that could happen. After we had done it once and I realized that it wasn’t at all like the kiss I was used to … as you can tell from the movie, he nearly takes my head off, so there was no danger of that.