Head movements, facial expressions and feedback in conversations: empirical evidence from Danish multimodal data

This article deals with multimodal feedback in two Danish multimodal corpora, i.e., a collection of map-task dialogues and a corpus of free conversations in first encounters between pairs of subjects. Machine learning techniques are applied to both sets of data to investigate various relations between the non-verbal behaviour—more specifically head movements and facial expressions—and speech with regard to the expression of feedback. In the map-task data, we study the extent to which the dialogue act type of linguistic feedback expressions can be classified automatically based on the non-verbal features. In the conversational data, on the other hand, non-verbal and speech features are used together to distinguish feedback from other multimodal behaviours. The results of the two sets of experiments indicate in general that head movements, and to a lesser extent facial expressions, are important indicators of feedback, and that gestures and speech disambiguate each other in the machine learning process.