NEWS IN FOCUS CANINE PSYCHIATRY Dogs provide genetic clues to human disorders µe PHYSICS Debate over meaning of Stephen Hawking's latest paper µ41 CLIMATE Developing nations struggle to keep carbon accounts p.451 CalSERVATMI Songbird killing for restaurants becomes a hot issue in Cyprus µS2 Go. a complex game popular in Asia. has I ustrated the efforts of artificial-intelligence researchers fordecades. ARTIFICIAL INTELLIGENCE Google masters Go Deep-learning software excels at complex ancient board game. BY ELIZABETH GIBNEY A computer has beaten a human professional for the first time at Go — an ancient board game that has long been viewed as one of the greatest challenges for artificial intelligence (Al). The best human players of chess, draughts and backgammon have all been outplayed by computers. But a hefty handicap was needed for computers to win at Go. Now Google's London-based Al company, DeepMind, claims that its machine has mastered the game. DeepMind's program AlphaGo beat Fan Hui, the European Go champion, five times out of five in tournament conditions, the firm reveals in research published in Nature on 27 January'. It also defeated its silicon-based rivals, winning 99.8% of games against the current best programs. The program has yet to play the Go equivalent of a world chant- pion, but a match against South Korean pro- fessional Lee Sedol, considered by many to be the world's strongest player, is scheduled for March. "We're pretty confident," says Deep- Mind co-founder Demis Hassabis. "This is a really big result, it's huge," says Kenn Coulom, a programmer in Lille, France, who designed a commercial Go program called Crazy Stone.1-le had thought computer mastery of the game was a decade away. The IBM chess computer Deep Blue, which famously beat grandmaster Garry Kasparov in 1997, was explicitly programmed to win at the game. But AlphaGo was not preprogrammed to play Go: rather, it learned using a general-