Synchrony in prosodic and linguistic features between backchannels and preceding utterances in attentive listening

In human-human dialogue, especially in attentive listening such as counseling, backchannels play an important role. Appropriately coordinated backchannels will not only make smooth communication but also help establish rapport. By collecting counseling dialogue, we investigate whether and how synchrony is expressed by prosodic and linguistic features of backchannels with respect to the preceding speaker's utterances. First, we find out correlation patterns according to the type of backchannels and prosodic features; a larger correlation is observed for reactive tokens than acknowledging tokens and for the power features than the pitch features. Next, we investigate the relationship between the morphological complexity of backchannels and the syntactic complexity of the preceding clause/sentence unit. The result can be useful for generating a variety of backchannels adaptive to the speaker's utterances.