In this paper, we propose natural reflexive behaviors for wheeled inverted pendulum type humanoid robots and show that such behaviors change human impressions of the robot. To achieve human-like communication between humans and robots, the latter need to be recognized by the former as communication partners. We believe that the natural reflexive behaviors of robots play an important role in being human partners. To validate the evidence, we generate four types of reflexive robot behaviors when pushed by someone and conducted preliminary experiments with subjects. We verified that people change their impressions of extroversion, agreeableness, intellect, and neuroticism for the robot by changing the reflexive behaviors. ©2006 IEEE.