Vocal reaction times to speech offsets: Implications for processing models of conversational turn-taking

Everyday conversation is characterized by a rapid alternation of turns among successive speakers. We investigate vocal reaction times to speech offsets in order to shed light on the limits of reactive behavior in conversational turn-taking. Twenty-three speakers of Dutch produced a prepared response ([ja], ‘yes’) as fast as possible in response to (a) the onset of a pure tone preceded by a variable amount of silence, and (b) the offset of several types of speech-like auditory stimuli varying in duration, prosodic characteristics, and speech rate. Reactions to the offset of stimuli lacking final prosodic cues were significantly longer than reactions to stimulus onsets (283 vs. 215 ms on average), and were rare below 200 ms (3%). Speaking latencies decreased as prosodic cues appeared further away from the stimulus end. Slowing down the speech rate produced an entrainment effect (i.e. slower responses) for stimuli lacking prosodic cues vs. a facilitatory effect (i.e. faster responses) when prosodic cues were present. These findings suggest that smooth turn transitions taking less than 200 ms are unlikely to involve reactions to silence at the end of a turn, but that they can be achieved when turn-final prosodic cues are available