The AP has a pretty good article on a humans vs. computer poker match set to start tomorrow at a conference on artificial intelligence in Vancouver. The article does a nice job of explaining exactly why poker is seen as an interesting challenge by artificial intelligence researchers.
The game-tree approach doesn’t work in poker because in many situations there is no one best move. There isn’t even a best strategy. A top-notch player adapts his play over time, exploiting his opponent’s behavior. He bluffs against the timid and proceeds cautiously when players who only raise on the strongest hands are betting the limit. He learns how to vary his own strategy so others can’t take advantage of him.
That kind of insight is very hard to program into a computer. You can’t just give the machine some rules to follow, because any reasonably competent human player will quickly intuit what the computer is going to do in various situations.
I’m definitely gonna be on the lookout for the results of this test. Sounds like a fun conference.