1. A robot apparatus capable of performing autonomous motion based on inner states and/or external stimuli, comprising expression means having a plurality of expressive units capable of being orthogonally expressed independently of one another; correlating means for correlating a plurality of orthogonal states, which are based on said inner states and/or external stimuli, with at least one of said expressive units; and control means for controlling said expression means for representing the plural orthogonal states in parallel, using the correlated expressive units.