HONG KONG — It’s all over for humanity — at least in the game of Go.
For the second game in a row, a Google computer program called AlphaGo beat the world’s best player of what many consider the world’s most sophisticated board game. AlphaGo is scheduled to play its human opponent, the 19-year-old Chinese prodigy Ke Jie, one more time on Saturday in the best-of-three contest.

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But with a score of 2-0 heading into that final game, and earlier victories against other opponents already on the books, AlphaGo has proved its superiority.

The Chinese Go master Ke Jie during his second game against AlphaGo, an artificial intelligence program, in Wuzhen, near Shanghai, on Thursday.© China Stringer Network, via Reuters The Chinese Go master Ke Jie during his second game against AlphaGo, an artificial intelligence program, in Wuzhen, near Shanghai, on Thursday.
Discussing the contest afterward, Mr. Ke said a very human element got the better of him: his emotions. In the middle of the game, when he thought he might have had a chance at winning, he got too keyed up, he said.

“I was very excited. I could feel my heart bumping,” Mr. Ke said after the contest, which took place in Wuzhen, near Shanghai. “Maybe because I was too excited I made some stupid moves.”

“Maybe that’s the weakest part of human beings,” he added.

AlphaGo’s victory on Thursday simply reinforced the progress and power of artificial intelligence to handle specific but highly complex tasks. Because of the sheer number of possible moves in Go, computer scientists thought until recently that it would be a decade before a machine could play better than a human master.

A small consolation for Mr. Ke was that he played a near-perfect game for the first hundred moves, according to the scientists who designed AlphaGo.

Still, like a sprinter who can at first keep pace with a train, in the end Mr. Ke was left in the dust by the computer.

Demis Hassabis, the co-founder of DeepMind — the artificial intelligence arm of Google’s parent, Alphabet Incorporated, that created the software — said that as he watched how close the game was, his pulse rate went up as well.

AlphaGo of course has no heart and feels no nerves, and in the end that may have helped make the difference. Scientists and futurists have pointed to that cold focus as a major reason artificial intelligence may someday take over large numbers of white-collar jobs. Still, that detachment means AlphaGo lacks the human touch required to manage employees, counsel patients or adequately write flowing newspaper features about its own dominance over humans.

Tests of the technology in games like Go still mark an early step. Because the strategy options are limited to moves on a board, games like Go are particularly suited to the technology.

Computer scientists say that often the best use of artificial intelligence is not to pit it against humans, but to pair it with them.

To that end, two Go professionals, each partnered with AlphaGo, are scheduled to play against each other on Friday. Mr. Hassabis has said that top amateur Go players, with the help of AlphaGo, can generally manage to beat the software program in a match. In short, a human with a computer is still stronger than a computer.

Ke Jie has said that after the third game on Saturday, he will return to focusing on playing against humans, and is not likely to take on a computer again, arguing that the technology has become too formidable.

“After this time, AlphaGo to me is 100 percent perfection, to me AlphaGo is the god of the Go game,” he said after the game on Thursday.

“For human beings,” he added, “our understanding of this game is only very limited.”