A key idea in understanding the proper use of the doubling cube on a practical level is that of the “benchmark” position. A benchmark cube situation is a position where one of the decisions (doubling or taking) is a toss-up, while the other is completely clear. Properly understanding a benchmark position is very useful since it unlocks the key to many related positions. Just compare your actual position to the benchmark, spot what the relevant differences, and you should be able to make a good cube decision over the board.
“Black on roll, cube action?”
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This early cube decision shows an excellent benchmark position. Orange started the game with a 5-1, splitting his back men, and Black responded with a 4-4, making two inner-board points. (Not best, by the way; making the 20-point and the 9-point is better, with a more enduring positional edge.) Orange then danced, and Black is now contemplating a double.
An analysis by the Extreme Gammon program (highly recommended, by the way) showed that the double/no double decision was completely marginal, with only a tiny difference between the two plays. If doubling is theoretically marginal, then taking is, of course, hugely correct. Dropping is a mistake costing almost one-third of a point. (As a practical matter, this means that doubling is mandatory, since it theoretically costs nothing and might prompt a huge blunder on your opponent’s part.)
Better players are aware of hundreds of good benchmarks, so they can make their over-the-board decisions quickly and accurately.
