redsales: Okay, so we agree that the doubling cube (especially when taken to the extreme) involves different thinking. At the more basic levels it means assigning a probability to a position, a skill which is quite dissimilar to the major one of chequer play, ranking the possible moves). At the higher levels it involves mathematics and memory (eg. remembering match equity tables).

We also agree that both the doubling cube and the castling rule introduce additional skills into their games.

So now I wonder about the degree of these additional skills. The discussion started with the idea that doubling introduces sufficient difference to warrant a separate identity.

Let's look within the backgammon arena. Hypergammon has exactly the same rules as Backgammon but has fewer men. This adds "additional skills" but I'd be hard pressed to argue that they are sufficient to claim that the thinking is different from that used in Backgammon. The tactics and strategies may be different but the thinking is still a question of ranking possible moves. Deciding that order is the same as in Backgammon but with more emphasis on probabilities and less on creating structure (ha ha, structure?). I'd say that any claim regarding additional skills can only be made in terms of emphasis rather than newness. Yet, while I can't put forward any additional cognitive functions, the game is obviously very different to Backgammon.

Considering Nackgammon we find that the additional skills argument is even more tenuous. It's almost pure Backgammon but with two men moved. Again it's a very different game, not drastically so as in Hypergammon, but still enough to give it a separate identity.

Now let's consider Chess. The castling rule adds additional skills in a quantitative way however I can't see that additional ways of thinking are required to tackle a castled king. As in Hypergammon there are new tactics involved, but no new brain function.

Chess has its nackgammons, too, with Fischer Random, Gothic, CRC. These may change strategic and tactical thinking but make little, if any, demand on new cognition. Yet these are branded as distinct variations. The different setups change the course of the game, taking the player through different areas of the game space, and that provides them with a distinctive feel.

The castling rule doesn't affect the whole game in the may that having only three does men in Hypergammon, or a different setup. Maybe that's why it's not a separate game from non-castling chess.

So where am I going with this? Well, the "additional skills" examples are almost all the same cognition but different game space. They still, however, make for separate games.

The doubling cube requires skills additional by an "order of magnitude", different cognition; doubling is pervasive, the option to double has to be considered by a player for every move while there's access to the cube; it means that a set of matches is no longer a collection of discrete games but an ordered sequence (cube decisions in later games are based on the match score). I haven't even mentioned the effect that gammons and backgammons have on the game, though they are a change that goes hand in hand with the introduction of the cube.

All of these things mean that Backgammon with the cube is a substantially different game to that without. Merely changing the position of two men has been enough to make a new variation. I suggest that doubling more than qualifies Backgammon for similar treatment.

The final point; we can elect not to have the cube in a game. In what other game is there the option to remove a complete chunk of rules and game play? Take Cylinder Chess, for example. The only difference from standard Chess is the wrap-around of the board. Can you imagine making that an option of standard Chess which players may switch on when they create a game invitation? They would both be called Chess and all games would contribute to the same BKR. You could look at a players played/won/drew/lost stats and BKR and have no idea what contribution was made by the two variations. Some players would never play the Cyclinder sub-variety, others may specialise. What would the Chess community's reaction be to that?


Given the above arguments I believe that Backgammon with the cube sharing the same identity as Backgammon sans cube has no basis in terms of the game itself. It's a pragmatic decision which keeps the number of Backgammon variations down for simplicity. There are 26 variations of Chess, only 6 of Backgammon. If we were to have doubling cube variations of those 6 then Backgammon would be in danger of catching up with Chess, especially as each new Backgammon would introduce 2 variations. [Lol, sorry Fencer, I couldn't resist that one! ]