like dimension, for we might ask a person to wrestle an arm protrud- ing through a curtain without seeing what the arm is attached to. After wrestling, and perhaps losing, we ask the human to judge whether the arm’s owner is human or artificial—and not only by the strength of the arm, but also by the strategy and tactics employed by the brain controlling the arm.
Building persuasively human artificial limbs and bodies is more than a matter of mechatronics or the faithful modeling of the human form. If an artificial arm is to do well at arm-wrestling, it must include sensory abilities that determine what the opposing arm is doing, such as judging the strength and direction of the forces it exerts, and it must draw on cognitive abilities to interpret that information and work out effective defensive and offensive movements. Just as a chess- playing computer has to weigh the moves made by its human oppo- nent and develop an opposing mental strategy, an arm-wrestling artificial being must assess its opponent’s physical behavior and work out a physical strategy.This kind of intelligent response requires artifi- cial sensing and artificial thinking, the subjects of the next chapters.