The ability of a robot to do gaze-drawing and to gesture have become recognized as essential elements in achieving joint attention of the real world during human-robot interaction. However, the ability of a robot using such non-verbal actions to interrupt human action is unclear. We have conducted an experiment in which a robot tries to interrupt human action to demonstrate the effectiveness of an interactive robot acting simultaneously with a person. Using the results of this experiment, we developed a system that a robot can use to predict human motion so that the robot can automatically perform simultaneous behavior.