Knowing when to respond: the role of visual information in conversational turn exchanges.

When engaging in conversation, we efficiently go back and forth with our partner, organizing our contributions in reciprocal turn-taking behavior. Using multiple auditory and visual cues, we make online decisions about when it is the appropriate time to take our turn. In two experiments, we demonstrated, for the first time, that auditory and visual information serve complementary roles when making such turn-taking decisions. We presented clips of single utterances spoken by individuals engaged in conversations in audiovisual, auditory-only or visual-only modalities. These utterances occurred either right before a turn exchange (i.e., 'Turn-Ends') or right before the next sentence spoken by the same talker (i.e., 'Turn-Continuations'). In Experiment 1, participants discriminated between Turn-Ends and Turn-Continuations in order to synchronize a button-press response to the moment the talker would stop speaking. We showed that participants were best at discriminating between Turn-Ends and Turn-Continuations in the audiovisual condition. However, in terms of response synchronization, participants were equally precise at timing their responses to a Turn-End in the audiovisual and auditory-only conditions, showing no advantage of visual information. In Experiment 2, we used a gating paradigm, where increasing segments of Turns-Ends and Turn-Continuations were presented, and participants predicted if a turn exchange would occur at the end of the sentence. We found an audiovisual advantage in detecting an upcoming turn early in the perception of a turn exchange. Together, these results suggest that visual information functions as an early signal indicating an upcoming turn exchange while auditory information is used to precisely time a response to the turn end.