1. A computer-implemented method for facial analysis comprising: collecting a series of images of a face; evaluating an image from the series of images with a classifier; flipping the image to create a flipped image; evaluating the flipped image with the classifier; comparing results from the evaluating of the image and the evaluating the flipped image; identifying an asymmetrical expression on the face based on the comparing; inferring mental states based on the asymmetrical expression wherein the mental states include a mental state of disbelief; and scoring the asymmetrical expression based on the comparing, wherein the left and right sides of the face are different, and wherein the scoring provides a probability of a facial expression occurring, wherein the scoring includes: providing a histogram computed from the image to a classifier to produce a first output; providing a histogram computed from the flipped image to a classifier to produce a second output: and computing a difference between the first output and the second output by subtracting the second output from the first output.