Facial Expression Representation Based on Timing Structures in Faces

This paper presents a method for interpreting facial expressions based on temporal structures among partial movements in facial image sequences. To extract the structures, we propose a novel facial expression representation, which we call a facial score, similar to a musical score. The facial score enables us to describe facial expressions as spatio-temporal combinations of temporal intervals; each interval represents a simple motion pattern with the beginning and ending times of the motion. Thus, we can classify fine-grained expressions from multivariate distributions of temporal differences between the intervals in the score. In this paper, we provide a method to obtain the score automatically from input images using bottom-up clustering of dynamics. We evaluate the efficiency of facial scores by comparing the temporal structure of intentional smiles with that of spontaneous smiles.