After six games, Carlsen leads by two points, with four draws added to the tally. Anand seems hell bent on founding a campaign to abolish the advantages of playing with the white pieces.

I find two aspects of the match notable so far. First, in the last two endgames Carlsen has been outplaying the computer programs (and Anand), sometimes for dozens of moves in a row. That isn’t easy, to say the least. And kudos to Alan Turing for realizing early on, in his 1953 paper, that chess-playing computer programs would face special difficulties in understanding some endgames. The sequences required to establish the importance (or not) of a measurable material advantage can stretch beyond the time horizon of the program, for instance, and the endgame tablebases take us only so far.

Second, Carlsen is demonstrating one of his most feared qualities, namely his “nettlesomeness,” to use a term coined for this purpose by Ken Regan. Using computer analysis, you can measure which players do the most to cause their opponents to make mistakes. Carlsen has the highest nettlesomeness score by this metric, because his creative moves pressure the other player and open up a lot of room for mistakes. In contrast, a player such as Kramnik plays a high percentage of very accurate moves, and of course he is very strong, but those moves are in some way calmer and they are less likely to induce mistakes in response.

Nettlesomeness is an underrated concept in our world, and kudos to Ken for bringing it to our attention. It should play a larger role in formal game theory than it does currently. It’s already playing a decisive role in the world of chess.

Addendum: Here are some of Ken’s metrics for “nettlesomeness.”