Engagement recognition by a latent character model based on multimodal listener behaviors in spoken dialogue

Engagement represents how much a user is interested in and willing to continue the current dialogue. Engagement recognition will provide an important clue for dialogue systems to generate adaptive behaviors for the user. This paper addresses engagement recognition based on multimodal listener behaviors of backchannels, laughing, head nodding, and eye gaze. In the annotation of engagement, the ground-truth data often differs from one annotator to another due to the subjectivity of the perception of engagement. To deal with this, we assume that each annotator has a latent character that affects his/her perception of engagement. We propose a hierarchical Bayesian model that estimates both engagement and the character of each annotator as latent variables. Furthermore, we integrate the engagement recognition model with automatic detection of the listener behaviors to realize online engagement recognition. Experimental results show that the proposed model improves recognition accuracy compared with other methods which do not consider the character such as majority voting. We also achieve online engagement recognition without degrading accuracy.