1. An autonomous robot apparatus having an emotion model, or a modeled emotion, and capable of expressing the own emotion, comprising: emotion management means for detecting and supervising the emotion of the robot apparatus; a plurality of behavior describing modules, each describing a preset behavior; and behavior selection means for selecting one or more of said behavior describing modules for demonstrating the behavior described in the behavior describing module selected; wherein when one of the behavior describing modules is selected by said behavior selection means, said selected behavior describing module causes a change in a basic posture as a posture at each beginning time point of one or plural motions forming the behavior described in the selected behavior describing module, responsive to the current emotion detected by said emotion management means, and wherein the selected behavior describing module ends the motion with a same posture as the posture at the beginning time point of the motion.