Techniques are disclosed for training a machine learning model to predict user expression. A plurality of images are received, each of the plurality of images containing at least a portion of a user's face. A plurality of values for a movement metric are calculated based on the plurality of images, each of the plurality of values for the movement metric being indicative of movement of the user's face. A plurality of values for an expression unit are calculated based on the plurality of values for the movement metric, each of the plurality of values for the expression unit corresponding to an extent to which the user's face is producing the expression unit. The machine learning model is trained using the plurality of images and the plurality of values for the expression unit.