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要旨

Information in language is organized according to a principle called information structure: new and important information (focus) is highlighted and distinguished from less important information (non-focus). Most studies so far have been concerned with how focused information is emphasized linguistically and suggest that listeners expect focus to be accented and process it more deeply than non-focus (Wang et al., 2011). Little is known about how listeners deal with non-verbal cues like beat gestures, which also emphasize the words they accompany, similarly to pitch accent. ERP studies suggest that beat gestures facilitate the processing of phonological, syntactic, and semantic aspects of speech (Biau, & Soto-Faraco, 2013; Holle et al., 2012; Wang & Chu, 2013). It is unclear whether listeners expect beat gestures to be aligned with the information structure of the message. The present ERP study addresses this question by testing whether beat gestures modulate the processing of accented-focused vs. unaccented-non focused words in context in a similar way. Participantswatched movies with short dialogues and performed a comprehension task. In each dialogue, the answer “He bought the books via amazon” contained a target word (“books”) which was combined with a beat gesture, a control hand movement (e.g., self touching movement) or no gesture. Based on the preceding context, the target word was either in focus and accented, when preceded by a question like “Did the student buy the books or the magazines via Amazon?”, or the target word was in non-focus and unaccented, when preceded by a question like “Did the student buy the books via Amazon or via Marktplaats?”. The gestures started 500 ms prior to the target word. All gesture parameters (hand shape, naturalness, emphasis, duration, and gesture-speech alignment) were determined in behavioural tests. ERPs were time-locked to gesture onset to examine gesture effects, and to target word onset for pitch accent effects. We applied a cluster-based random permutation analysis to test for main effects and gesture-accent interactions in both time-locking procedures. We found that accented words elicited a positive main effect between 300-600 ms post target onset. Words accompanied by a beat gesture and a control movement elicited sustained positivities between 200-1300 ms post gesture onset. These independent effects of pitch accent and beat gesture are in line with previous findings (Dimitrova et al., 2012; Wang & Chu, 2013). We also found an interaction between control gesture and pitch accent (1200-1300 ms post gesture onset), showing that accented words accompanied by a control movement elicited a negativity relative to unaccented words. The present data show that beat gestures do not differentially modulate the processing of accented-focused vs. unaccented-non focused words. Beat gestures engage a positive and long lasting neural signature, which appears independent from the information structure of the message. Our study suggests that non-verbal cues like beat gestures play a unique role in emphasizing information in speech.