Rooney Mara arrived at the Sundance Film Festival for the premiere of her latest film The One I Love. So far, the beauty looks coming out of Park City, UT, have all been on the casual side — topknots, waves, and fresh-faced makeup. Rooney's style kept with the trend in terms of her makeup: she sported bold brows, a peachy flush, and little else. But the actress's casual updo has us stumped. The uneven tendrils around her face make us think it's a laissez-faire version of the faux bob. But from the side shot, it could also be a mussed bun, which is one of Rooney's favorite hairstyles. Faux bob or chignon? We're not sure. So we need your help to classify this 'do.