Neural and Behavioral Dynamics of Predictive Speech Planning

Timing and prediction are fundamental components of conversational dynamics, particularly in the estimation of turn-taking. While neural markers of predictive processing have been proposed in comprehension, their counterparts in speech production remain less well understood. In this study, we investigated these mechanisms using a combined EEG and behavioral approach with an oral sentence completion task. Participants viewed images that prompted them to produce a word completing a subsequently heard sentence. We systematically manipulated sentence repetition, length, and cloze probability to assess their effects on speech production timing and associated neural activity, focusing specifically on the readiness potential (RP) as an index of motor preparation. Our findings revealed that high-cloze-probability sentences elicited faster RTs, but only when participants had not yet formed predictions and when the sentences were relatively short. These faster RTs were also associated with a different RP amplitude. Moreover, RP dynamics were predictive of speech onset, suggesting that motor preparation plays an active role in response timing. Together, these results support a predictive decision-making framework for speech production, in which comprehension, prediction, and motor execution form a continuous, interactive process.