Maria Sonin, 33, an office worker in Waltham, Mass., sat in front of a notebook computer looking at a movie trailer while Affectiva’s software, through the PC’s Webcam, calibrated her reaction. The trailer was for “Little Fockers,” starring Robert De Niro and Ben Stiller, which opened just before Christmas. The software measured her reactions by tracking movements on a couple of dozen points on her face — mostly along the eyes, eyebrows, nose and the perimeter of her lips.