In this paper, we report the importance of the reactive behaviors of humanoid robots against human actions for smooth communication. We hypothesize that the reactive behaviors of robots play an important role in achieving human-like communication between humans and robots since the latter need to be recognized by the former as communication partners. To evaluate this hypothesis, we conducted psychological experiments in which we presented subjects with four types of reactive behaviors resulting from pushing a wheeled inverted-pendulum-type humanoid robot. From the experiment, we found that subject's impressions to the robot regarding extroversion and neuroticism changed by the robot's reactive behaviors. We also discuss the reasons for such changes in impressions by comparing the robot's and human reactive behavior.
