Multimodal feedback signals in dyadic conversations

In this study the use of embodied feedback signals in the form of head nods -- specifically as they occur in spontaneous German conversation -- is described and compared to the use of vocal feedback signals known as backchannels (BC). For this purpose, the paper traces the notion of conversational feedback in both embodied and vocal modalities. Head nods are conceptualised as an embodied counterpart to the notion of vocal BCs, which are short vocal utterances that listeners employ to provide feedback to their interlocutors. In the data analysed, head nods were on average 1139 ms long, approximately four times longer than vocal BCs at 299 ms. The central finding connected to this, is that head nods start before, and end after vocal BCs -- essentially enveloping the vocal BCs. Two thirds of nods occur as pro-speech gestures, not co-occurring with vocal BCs. The lexical type and prosodic contour of BC do not appear to have an influence on the co-occurrence of a nod.