since the dawn of human ingenuity, people have devised ever more cunning tools to cope with work that is dangerous, boring, burdensome, or just plain nasty. that compulsion has resulted in robotics—the science of conferring various human capabilities on machines. and if scientists have yet to create the mechanical version of science fiction, they have begun to come close.

　　　as a result, the modern world is increasingly populated by intelligent gizmos whose presence we barely notice but whose universal existence has removed much human labor. our factories hum to the rhythm of robot assembly arms. our banking is done at automated teller terminals that thank us with mechanical politeness for the transaction. our subway trains are controlled by tireless robo-drivers. and thanks to the continual miniaturization of electronics and micro-mechanics, there are already robot systems that can perform some kinds of brain and bone surgery with submillimeter accuracy—far greater precision than highly skilled physicians can achieve with their hands alone.

　　　but if robots are to reach the next stage of laborsaving utility, they will have to operate with less human supervision and be able to make at least a few decisions for themselves—goals that pose a real challenge. "while we know how to tell a robot to handle a specific error," says dave lavery, manager of a robotics program at nasa, "we can