In her review of Brothers, Slate's Dana Stevens discloses
Here I come up against what I'm fully willing to admit may be a personal limitation: I can't stand Natalie Portman. I've never believed her in a single role. She evokes no emotional response in me beyond, "Oh, there's Natalie Portman." She doesn't overact or underact; she just stands around with whatever the appropriate expression for the scene seems to be on her sweet, pretty, childlike face. If there's something going on behind that face, I neither know nor care what it is, which means that long stretches of Brothers involving her character's interiority struck me as dramatically inert. If you possess the gene that enables Portman-caring, you may find them brilliant.
I think Portman was wonderful as a teenage actress — in “The Professional,” of course (her breakout, and still her best role), but also in “Beautiful Girls” and “Heat” as well. But she’s had the same problem that Leonardo DiCaprio had (and still has, despite his permanent stubble, and Martin Scorsese’s best efforts) making the transition to grown-up parts. Like Leo, she looks younger than she is, and the qualities that made her appealing in teenage roles (a kind of luminous transparency, above all) make her hard to take seriously when she plays a stripper, or a terrorist, or a scheming Ann Boleyn — or, in this case, an army wife and mother of two....
Tellingly, just as DiCaprio’s best role in the last decade was as a charming man-child in “Catch Me If You Can,” Portman’s best turn was playing the manic pixie dream girl in Zach Braff’s “Garden State.” She was magnetic, albeit in a mediocre and pretentious movie — but it was a throwback to the kind of girlish part that made her famous, rather than a leap into the kind of adult work that she keeps trying, and failing to quite pull off.
With a meaningful caveat, I tend to agree. As I wrote in my review of Closer back in 2005
Early in her career, when she played child characters (The Professional, Beautiful Girls), she seemed old beyond her years. But somehow as she's graduated to adult roles she seems ever more like a child, as though she's shrinking before our eyes. (When, early in Closer, she jokingly describes herself as a "waif," the comment strikes a little too close to the mark.) Portman's tiny stature and delicate features contribute to this impression, of course, but there's more to it than that. As her star has ascended she's seemed somehow less and less touched by real life. For a while it was possible to put this off on her turn as George Lucas's child-queen. But in Closer, as in Garden State (and even her small role in Cold Mountain), there's something disconcertingly girlish about her.
The caveat is that Brothers, directed by Jim Sheridan, is the first film in which I have found Portman persuasive in an adult role--indeed, the one in which I think she may have given her most focused and mature performance to date. (To be fair, it's not clear whether Graham or Douthat have seen the film.) Portman plays Grace Cahill, wife of Captain Sam Cahill, USMC (Tobey McGuire). When her straight-arrow husband is sent back for another tour in Afghanistan, she leans for help on his ne'er-do-well, recently paroled brother Tommy (Jake Gyllenhaal). And when Sam's chopper crashes and he's declared dead, Tommy gradually inherits his role in the family, caring for Grace's two daughters and carving out some small space in her heart as well.
But Sam is not dead; he has been captured, and tortured, and ultimately made to do terrible things. And when he returns home, full of paranoia and self-loathing, to discover his brother's usurpment, the fraternal roles are reversed, with Tommy now the beacon of stability and Sam the dangerous wild card.
There are considerable problems with the latter half of the film. Sam's culminating horror in Afghanistan feels unearned and unrealistic, which is a pity, given how many more plausible situations could have accomplished the same result. Similarly, a dinner-table outburst by one of the young girls after Sam's return takes a form it is very difficult to imagine coming from one so young--again, frustrating when there are so many other things she might more credibly have said that would have served identical narrative ends. In part thanks to these two crucial, overheated moments, Sam's character goes too far around the bend, dragging the film with him. By the end, it's hard to shake the sense that Brothers has inadvertently painted itself into a corner.
Which is a shame, because in its first half (and intermittently in the second), the film is one of the most minutely observed character studies of recent years, and this is thanks not only to director Sheridan, but to exceptional performances by Gyllenhaal (whom I've never seen better), by Bailee Madison and Taylor Geare as the young girls (two of the best child performances onscreen in many, many moons) and, yes, by Portman. The role is not an easy one--Grace is, after all, primarily the axis around which the brothers revolve--but Portman conveys it with tender nuance and a groundedness I had never seen, nor expected to see, from her before. Where previous performances have been characterized by something tinny, even a tad nervous, here Portman seems to have slowed down, to have mellowed. Her anxiety and despair, her love for her girls and gratitude toward Tommy--all are richly intertwined and seem to emanate from deep within, rather than merely playing upon the surface. Brothers is far from a perfect film, but thanks to Portman, Gyllenhaal, Madison, and Geare (and the pre-psycho McGuire) it's well worth seeing.