Affect bursts: dynamic patterns of facial expression.

Affect bursts consist of spontaneous and short emotional expressions in which facial, vocal, and gestural components are highly synchronized. Although the vocal characteristics have been examined in several recent studies, the facial modality remains largely unexplored. This study investigated the facial correlates of affect bursts that expressed five different emotions: anger, fear, sadness, joy, and relief. Detailed analysis of 59 facial actions with the Facial Action Coding System revealed a reasonable degree of emotion differentiation for individual action units (AUs). However, less convergence was shown for specific AU combinations for a limited number of prototypes. Moreover, expression of facial actions peaked in a cumulative-sequential fashion with significant differences in their sequential appearance between emotions. When testing for the classification of facial expressions within a dimensional approach, facial actions differed significantly as a function of the valence and arousal level of the five emotions, thereby allowing further distinction between joy and relief. The findings cast doubt on the existence of fixed patterns of facial responses for each emotion, resulting in unique facial prototypes. Rather, the results suggest that each emotion can be portrayed by several different expressions that share multiple facial actions.