When film critic A.O. Scott crowned her “the definitive screen actress of her generation” in a long essay in The NewYork Times in March, Greta Gerwig was too overwhelmed to read the whole thing. But she read enough to be “incredibly flattered that he thought so much about it,” she says, and to get the gist: Both in the no-budget features that jumpstarted her career and opposite Ben Stiller in the recent indie film Greenberg, Gerwig is not doing what we usually think of as acting.

“Her diction is more like what you hear at the next table in the local coffee bar than at the movies,” Scott asserted.

“She tends to trail off in midsentence, turn statements into questions or tangle herself up in a rush of words. She comes across as pretty, smart, hesitant, insecure, confused, determined—all at once or in no particular order. Which is to say that she is bracingly, winningly, and sometimes gratingly real.”

On a sticky August afternoon, I meet the suspect actress in the spacious, subtly quirky Chinatown flat she shares with two roommates and two kittens— Diane Kitten and Paw Newman. With her luminous hazel eyes, Gerwig proves pretty indeed. And she seems real enough—peppering her talk with pauses to think. But “confused” and“insecure”? “I am made of steel—you have no idea!” she exclaims in cartoon outrage, flexing one of the biceps she has been working on for the remake of the 1981 Dudley Moore vehicle Arthur. She plays the love interest—the Liza Minnelli working-class waitress part—and has just come from a kickboxing session that the studio ordered. They want her as toned as possible. On a more serious note, she points out, “Directors know they don’t have to mollycoddle me. A lot of our conversations start with, ‘I’m just going to tell you this straight....’”

Gerwig is not surprised that people confuse her with her characters: “I like acting where you can’t see the performance,” and she works for that effect. For Greenberg, in which she plays a lovely personal assistant who cannot make it through a sentence without apologizing and is defenseless against the Stiller character’s misanthropic jabs, “I behaved with her gentleness and constant apologizing for the whole three months we were making the film,” she says. “It is easier to get there and stay there than to drop it every night. And it was hard to come out of, because I forgot who I was. When it’s working right, you’re just sort of swimming in it. It’s not that there’s no work behind it, it’s that the work is done and you’re letting it happen.” For Arthur, filming in Manhattan over the summer, she heads to the shoot even on days when she isn’t needed. “I’m hanging out and working on the character,” she explains. “I spent hours trying on costumes. You find [the character] by making a whole lot of wrong choices.” Plus, she likes “the feeling that we’re all making this together—everybody’s down in the trenches together.” The feeling is familiar.

Gerwig cut her teeth on a genre of low-distribution, festival-circuit film called “mumblecore” because of dialogue as casual as thinking—or noshing, which the 20-something characters do a great deal of. She starred in and co-wrote Hannah Takes the Stairs in 2007, about a young woman who muddles her way through romances with one coworker after another. And with the following year’s Nights and Weekends—as much a portrait of a generation as of a couple (Gerwig and codirector Joe Swanberg), who aim to be both friends and lovers and end up as neither—she added codirector and coproducer to her credits. The movies caught the attention of Greenberg writer- director Noah Baumbach.

Gerwig attributes her triple-threat status—writer, director, actress—to Barnard. The Sacramento native “always secretly wanted to be an actress,” she says, and planned on attending a conservatory. But her mother, a nurse, insisted she take the liberal arts route. Gerwig figured, Barnard was at least in New York.

The college experience turned out to be “genuinely life changing—everything converging and interlocking,” says this major in English and philosophy. “I got more excited about acting when I realized I could write scripts. And it was pretty killer to work on my own weird theatre, and then talk about Renaissance plays in English. I went to old art films and new art films running at the same time at Film Forum. I felt completely, dorkily jazzed.”

She also developed a point of view. She realized that she “responded to writing and acting where you feel someone doesn’t know what to say next. The acting becomes every moment the character is living in desperate uncertainty, but it feels that way in the whole theatre. The audience is like, ‘Oh, no! What is that person going to say now?!’”

A favorite example is Will Eno’s Pulitzer Prize–nominated Thom Pain (based on nothing), in which the title character, played by James Urbaniak, experiences “moments of deep discomfort where he would lose track of what he was saying, and you really felt that Urbaniak was losing track.” On the film front, she “likes gently watching people live in all their complexities.” The movies of Mike Leigh, for example, express “a genuine confusion around why people do what they do.”

Eventually Gerwig wants to get back to writing and directing, in “one of those long, crazy careers, Clint Eastwood-style.” But for now, with Arthur to finish and the first Whit Stillman film since his 1998 Last Days of Disco to shoot this fall, the acting—“that secret dream I quietly fed”—is more than enough.

-by Apollinaire Scherr, photograph by Sebastien Kim