Using the readiness potential of button-press and verbal response within spoken language processing

•Detection of readiness potential onset represents a preconscious measure for end-of-turn anticipation in a language dialogue.•Even if it is a language task it can be applied equally well to both verbal and finger movement responses.•In contrast to behavioural reaction time tasks the EEG-measurement produces more reliable data for the anticipation performance in end-of-turn-detection. Even though research in turn-taking in spoken dialogues is now abundant, a typical EEG-signature associated with the anticipation of turn-ends has not yet been identified until now. The purpose of this study was to examine if readiness potentials (RP) can be used to study the anticipation of turn-ends by using it in a motoric finger movement and articulatory movement task. The goal was to determine the preconscious onset of turn-end anticipation in early, preconscious turn-end anticipation processes by the simultaneous registration of EEG measures (RP) and behavioural measures (anticipation timing accuracy, ATA). For our behavioural measures, we used both button-press and verbal response (“yes”). In the experiment, 30 subjects were asked to listen to auditorily presented utterances and press a button or utter a brief verbal response when they expected the end of the turn. During the task, a 32-channel-EEG signal was recorded. The results showed that the RPs during verbal- and button-press-responses developed similarly and had an almost identical time course: the RP signals started to develop 1170 vs. 1190ms before the behavioural responses. Until now, turn-end anticipation is usually studied using behavioural methods, for instance by measuring the anticipation timing accuracy, which is a measurement that reflects conscious behavioural processes and is insensitive to preconscious anticipation processes. The similar time course of the recorded RP signals for both verbal- and button-press responses provide evidence for the validity of using RPs as an online marker for response preparation in turn-taking and spoken dialogue research.