A blunder cost chess legend Garry Kasparov the third in a series of championship games with supercomputer Deep Junior on Thursday.
"I had a complete blackout," Kasparov said. "Despite Deep Junior having a great team and grandmaster trainers, I had great positions."
Kasparov sacrificed a pawn, one his least-powerful pieces, hoping to further strengthen his position. But the sacrifice actually left him vulnerable, and Deep Junior capitalized on the mistake. Seeing few options, Kasparov conceded.
The six-game series is tied at 1 1/2 games each. Kasparov won the first game Sunday; the second on Tuesday was a draw. The next game is Sunday.
Kasparov, 39, said he becomes fatigued during the games, which can last for hours, while the computer doesn't.
"I have to work on that," he said.
The match is sanctioned by the World Chess Federation, which will pay Kasparov $500,000, and an additional $300,000 if he beats Deep Junior, which has not lost a match against a human in two years.
The games can be followed live on the Web site of X3D Technologies, one of the match's sponsors.
Kasparov lost to IBM supercomputer Deep Blue in 1997. He said the computer may have been given hints by humans.