As a result, the modern world is increasingly populated by intelligent robots whose presence we barely notice but whose universal existence has removed much human labor. 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 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 be able to make at least a few decisions for themselves. Despite a spell of initial optimism in the 1960s and 1970s when it appeared that transistor circuits and microprocessors might be able to copy the action of the human brain by the year 2010, researchers lately have begun to extend that forecast by decades if not centuries.