In this paper, we examine the effectiveness of intonational and gestural cues in understanding syntactically ambiguous Japanese sentences. In Tokyo Japanese, it is well known that syntactic ambiguous sentences are distinguished by the intonation. Moreover, in our previous study, it is reported that the intonational distinction decreases when gestures are accompanied by the utterance but the speakers are not aware of the fact. In this study, we examine whether gestures are effective cues in compensating for the loss of intonation for the hearers’ understanding. In the experiment, we created three types of stimuli: (i) audio of utterances whose speakers concentrated only on reading aloud ambiguous sentences, (ii) audio + video of utterances whose speakers gave gestures accompanied with ambiguous utterances, and (iii) audio extracted from (ii). The results show that the hearers were able to understand the meaning of ambiguous sentences when they listened to the audio of utterances without gesture more correctly than when they watched/listened to other stimuli. In addition, the hearers’ confidence in understanding the intended meaning was influenced by the type of stimuli, while the speakers’ confidence in their communication was not. The results indicate that the hearers understood the intended meaning more accurately when they listened to the utterances whose intonation patterns correspond to the syntactic structure than when they watched the videos with gestures. Moreover, the hearers were aware of this fact. We conclude that different means can be used effectively for speakers and hearers to communicate and understand intentions, respectively.
