Modeling facial signs of appraisal during interaction: impact on users' perception and behavior

Interactive virtual characters are expected to lead to an intuitive interaction via multiple communicative modalities such as the expression of emotions. Generating facial expressions that are consistent with the interaction context is a challenge. This paper presents our interactive facial animation system based on the Component Process Model, generating facial signs of appraisal during a real-time interactive game. We describe a study comparing our model to the categorical approach of facial animation of emotion. Participants interacted with a virtual character in three conditions: no expression of emotion, an expression of a categorical emotion, and expressions of sequential signs of appraisal. The character in the appraisal condition was reported as being more expressive than in the other two conditions and was reported as experiencing more mental states. In addition, using appraisal signs modified the way participants interacted with the character (participants played slower after some emotions were expressed by the agent, i.e. pride and sadness).