They became friends while co-starring in last year's Dogville. Now Nicole Kidman, 37, and Lauren Bacall, 80, play mother and daughter in the edgy new drama Birth. The two actresses are "kindred spirits," says Kidman. They've also had very similar lives, starting their careers early and working as single moms. They spoke with PEOPLE senior editor Jess Cagle.

Lauren, is it true you recently called Nicole a "beginner"?

BACALL: So boring. One reporter said, "Nicole's an icon and you're an icon." I said, "Why does she have to have a label? She's just beginning her career!" Then it was distorted.

You both started working very young. Do you think you missed out on your youth?

KIDMAN: I didn't become famous like Lauren became famous. You were 19 when you were catapulted.
BACALL: I didn't realize until after I had moved into my 20s—and by then I was married to Bogie [Humphrey Bogart] and having children—that I never really had a girlhood.
KIDMAN: How old were you when you had your first baby?
BACALL: 24.
KIDMAN: I was 25.
BACALL: At 15, I was working and I was thrilled to work.
KIDMAN: I started working at 15 too.

Birth is not a mainstream movie. You've both made a lot of surprising career choices.

BACALL: The reason that I was able to spread my wings was the stage. The theater gave me opportunities that movies would never give me. Nicole has taken more chances than I have.
KIDMAN: Lauren got on a plane and went to Sweden to work with [Dogville director] Lars von Trier. And left her dog. You don't understand. That's a big thing. Left Sophie!
BACALL: I left Sophie. My papillon. My partner. We all have our partners.
KIDMAN: I'm getting a cat in Australia. That's my partner.

When you're a single working mother, what are the advantages and disadvantages of being an actress?

BACALL: Well, the advantages are that you have children. The disadvantages are, because of your work, you can't spend as much time with them as you would like. I remember my son Steve, when he was in his teens, said to me, "I never saw you wear an apron." [Kidman and Bacall both laugh.] I said, "Really? I didn't bake cookies? What are you talking about? I was working!"
KIDMAN: Moulin Rouge was the first time my kids were really on the set a lot. Their memories are being in the trailer and me in a top hat and fishnets going, "Now here's your dinner." It's a bizarre childhood when you have a mother who's an actress. I hope at the same time there is some benefit. You get to see your mother onscreen, so when she's long gone you kind of have a part of her. Every time I do a film I write a letter to Connor and a letter to Bella talking about my ideas, how they somehow affected the movie, so they can feel like it's theirs.

What's it like trying to date when you're famous?

KIDMAN: [laughing] Oh, God.
BACALL: Don't look at me, kid.
KIDMAN: Don't look at me either!
BACALL: Men are so boring! They're so totally self-involved. Please.
KIDMAN: I wouldn't mind...
BACALL: You meet some interesting, terrific guy—
KIDMAN: That hasn't happened since my marriage.
BACALL:—but they don't bother to find out really what you're like, because they're so worried about what they're all about. It's absolutely true.

True, Nicole?

KIDMAN: [laughing] I hope not. But the way Lauren speaks about Humphrey Bogart, it's beautiful to hear.
BACALL: God knows I wouldn't have traded it for anything on earth, but when you have that kind of happiness when you're 19 years old, it's downhill after that.
KIDMAN: [laughing] You guys were hot!

Both of you, when you were getting your big breaks, fell in love with your costars.

BACALL: And that is something that one normally would not recommend.

Was it hard to concentrate while making the films?

KIDMAN: To be honest, it all became like, Who cares?

You often hear that it's harder to be an actress than an actor in Hollywood.

BACALL: I think it's very hard for anyone to live in L.A. and try to get work that's interesting. I think women are not given the opportunity that men are. And a woman alone, obviously, has a tougher time.
KIDMAN: I think it's very hard to be an actor or an actress. It's very easy to get corrupted. Neither of us live [in LA]. I mean, I lived there when I was married. But I was existing in a bubble.

Why do so many young actresses in Hollywood have plastic surgery?

BACALL: They're insane, that's one reason. The mood out there is, you absolutely cannot have a line on your face. They all look alike to me.
KIDMAN: You have to love your smile lines, you have to love your frown lines. Being 5'11" by the time you're 14, in some ways it gives you your character. It's torture at the time, but all those struggles are actually good. I say this to my daughter. As a mother, as a woman, you say be brave—and be proud not to be like everybody else.