Generating Natural Interactive Motion in Android Based on Situation-Dependent Motion Variety

Abstract

In order to develop a robot that can work in normal everyday situations, it is necessary to discover the principles relevant to establishing and maintaining social interaction between humans and robots. Even if short-term human-robot interaction can be performed by implementing simple behaviors in a robot, it remains difficult to realize long-term social interaction. We have explored the principles underlying natural human-robot communication by development of an android which closely resembles a human being, which is called an android science approach (Ishiguro, 2005). Nass et al. (Nass et al., 1994) demonstrated that the human-computer relationship is fundamentally social and that a person's social response toward computers is automatic in social situations. It is inferred from their studies that person's interpersonal responses subconsciously expressed toward a robot (in other words, perceptual social illusion (Jacob & Jeannerod, 2005)) underlie the natural communication between the person and the robot. The condition to elicit interpersonal behavior must be related to a mechanism to support natural communication. The android science approach explores the boundary conditions to elicit subconscious interpersonal behavior toward an android from humans by investigating methods to make the android more humanlike. Humanlike body motions are necessary to implement humanlike behavior in an android. There have been several studies on the generation of humanlike motion, including studies on a model to generate human motion trajectories based on a neurocomputational approach (Flash & Hogan, 1985; Uno et al., 1989; Kawato, 1992; Schaal & Sternad, 2001), a study on the control of a manipulator based on a model of motion trajectories of a person's arm (Kashima & Isurugi, 1998), and studies on a computer graphics (CG) animated characters, which have shown that noise in the motion makes the character's motion more humanlike (Perlin, 1995; Bodenheimer et al., 1999). These studies successfully generated a humanlike motion. However, a humanlike motion specific to communication situations has not been considered. The present study considers the human-like nature of a person's motion during interaction with other people. A person generally does not produce exactly identical motion when he/she repeats a behavior with the same intention, as shown in Fig. 1(a). In contrast, a robot is able to repeat exactly identical motion with a purpose. A person's motion is diverse in that the motion