Controlling Switching Pause Using an AR Agent for Interactive CALL System

We are developing a voice-interactive CALL (Computer-Assisted Language Learning) system to provide more opportunity for better English conversation exercise. There are several types of CALL system, we focus on a spoken dialogue system for dialogue practice. When the user makes an answer to the system's utterance, timing of making the answer utterance could be unnatural because the system usually does not make any reaction when the user keeps silence, and therefore the learner tends to take more time to make an answer to the system than that to the human counterpart. However, there is no framework to suppress the pause and practice an appropriate pause duration. In this research, we did an experiment to investigate the effect of presence of the AR character to analyze the effect of character as a counterpart itself. In addition, we analyzed the pause between the two person's utterances (switching pause). The switching pause is related to the smoothness of its conversation. Moreover, we introduced a virtual character realized by AR (Augmented Reality) as a counterpart of the dialogue to control the switching pause. Here, we installed the character the behavior of "time pressure" to prevent the learner taking long time to consider the utterance. To verify if the expression is effective for controlling switching pause, we designed an experiment. The experiment was conducted with or without the expression. Consequently, we found that the switching pause duration became significantly shorter when the agent made the time-pressure expression.