The effects of dual-task interference in predicting turn-ends in speech and music.

Determining when a partner's spoken or musical turn will end requires well-honed predictive abilities. Evidence suggests that our motor systems are activated during perception of both speech and music, and it has been argued that motor simulation is used to predict turn-ends across domains. Here we used a dual-task interference paradigm to investigate whether motor simulation of our partner's action underlies our ability to make accurate turn-end predictions in speech and in music. Furthermore, we explored how specific this simulation is to the action being predicted. We conducted two experiments, one investigating speech turn-ends, and one investigating music turn-ends. In each, 34 proficient pianists predicted turn-endings while (1) passively listening, (2) producing an effector-specific motor activity (mouth/hand movement), or (3) producing a task- and effector-specific motor activity (mouthing words/fingering a piano melody). In the speech experiment, any movement during speech perception disrupted predictions of spoken turn-ends, whether the movement was task-specific or not. In the music experiment, only task-specific movement (i.e., fingering a piano melody) disrupted predictions of musical turn-ends. These findings support the use of motor simulation to make turn-end predictions in both speech and music but suggest that the specificity of this simulation may differ between domains.

Listeners are better at predicting speakers similar to themselves.

Although it takes several hundred milliseconds to prepare a spoken contribution, gaps between turns in conversation tend to be much shorter. To produce these short gaps, it appears that interlocutors predict the end of their partner's turn. The theory of prediction-by-simulation proposes that individuals use their own motor system to model a partner's upcoming actions by referring to prior production experience. In this study we investigate the role of motor experience for both predicting a turn-end and producing a spoken response by manipulating the similarity of heard speech to participants' own production style. We hypothesised that they would be better at predicting, and initiating responses to, speech produced in the style they speak themselves. Participants recorded a series of questions in two sessions, and several months later they listened to their own speech and that of a stylistically similar and a stylistically dissimilar participant (as assessed by independent raters). Participants predicted the end of 60 of these questions by pressing a button, and for the remaining 60 questions, by producing a spoken response. An analysis of response times showed that participants' button-press responses were faster for utterances spoken by themselves and by a stylistically similar partner, than for utterances spoken by a stylistically dissimilar partner. We conclude that simulation facilitates prediction of similar speakers.