Medicine is an imprecise art, and medical error, whether through negligence or honest mistake, is shockingly common. Some experts believe it to be the third-biggest killer in the US. In the UK, as many as one in six patients receive an incorrect diagnosis from the National Health Service. One of the great promises of artificial intelligence is to drastically reduce the number of mistakes made in the world of health care. For some conditions, the technology is already approaching--and in some cases matching and even exceeding--the success rates of the best specialists. Researchers at the John Radcliffe Hospital in Oxford, for instance, claim to have developed an AI system capable of outperforming cardiologists in identifying heart-attack risk by examining chest scans.