Principles of the Doubling Cube

In one of my previous articles, I expressed my thoughts about the cube as unacceptable in the context of the philosophy of backgammon. I should also indicate that the doubling cube has been an inevitable part of the game since the 1920s… This cube which is used for increasing the bet, is included with almost every possible backgammon set you can find. This situation, however, is a little bit different in countries within the region of Mesopotamia (said to be where the game originated from). Very few people know about the cube from countries within this region including Turkey, Iran, Iraq, Syria and Israel. So let's explain the principles of the cube for those who don't know.

Each game starts with a 1 point bet. During the game, the leading party may use the doubling cube against his opponent. This is done by turning the cube over, such that it shows the next number in the sequence. Each face of the doubling cube contains a number from 2 to 64, where each number is a power of two. So it goes like 2, 4, 8, 16, 32, 64. At the beginning of the game, the cube is placed between two players, its 64 side looking upwards (since there is no 1 in the cube, 64 initially represents 1). Any time during the game, any party may use the cube by turning the 2 side upwards. Then each double must follow the sequence in order.

A player can only use the cube when it's his turn, and before rolling the dice. This is an offer, so the other party may accept or reject the offer. If the offer is rejected, then rejected party loses that game at one point. If the offer is accepted, then the bet doubles to two. Moreover, the player accepting a doubling offer becomes the owner of the cube, and puts the cube to his side (showing the new bet). After that, only the most recently accepted party can use the cube.

The next doubles are called "re-doubles". When one of the parties rejects a re-doubling offer, he has to pay the points before the offer. Otherwise he becomes the new owner of the cube and the game continues with the double from the previous bet. There are no limits on the number of doubles in a game.

Common sense tells us to reject the doubling offer if the game is not in our favor at the moment of the offer. This is a tricky situation; let's examine the two scenarios given below:

1. Four games in a row, Player A doubles the bet and Player B rejects all offers. As a result, Player B falls behind four points (-4).
2. Four games in a row, Player A doubles the bet and Player B accepts all the offers. Player B loses four games and wins one game. He loses 2 points for each game he loses (-6) and earns 2 points for his single victory (+2). The net result is -4 points, just like in the first scenario.

So, this is the basic principle of doubling: If you have a 25 per cent chance of winning, you can (must) accept the doubling offer.

The situation is often much more complex though. Because of the cube owner rule, psychology of the player, gammons and backgammons (and match scores in the matches), there are lots of things to consider. In such cases, the bet in the doubling cube is multiplied by the game points. This is a subject for future articles. That's all for now...

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