How machine learning works

THE standard joke about artificial intelligence (AI) is that, like nuclear fusion, it has been the future for more than half a century now. In 1958 the New York Times reported that the Perceptron, an early AI machine developed at Cornell University with military money, was "the embryo of an electronic computer that [the American Navy] expects will be able to walk, talk, see, write, reproduce itself and be conscious of its existence". Five decades later, self-aware battleships remain conspicuous by their absence. Yet alongside the hype, there has been spectacular progress: computers are now better than any human at the games of chess and Go, for instance. Computers can process human speech and read even messy handwriting.