We have been doing a research on visionbased reinforcement learning and applied the method to build real soccer playing robots. In the rst stage [ Asada et al., 1994a ] , a robot learned to shoot a ball into a goal. In the second stage [ Asada et al., 1994b; Asada et al., 1994c ] , we set up an opponent just before the goal, that is, a goal keeper, and make the robot learn to shoot a ball into ...