Chess or jass: what requires more intelligence?

(Jass is a very popular Swiss card game of the same family as whist and bridge, though more homespun than the latter.)

Generally, it is assumed that chess requires more intelligence, for obviously less intelligent players definitely stand a chance of winning at cards while they don’t in chess. If we consider, however, what a computer program must be able to do in order to win, the picture soon looks different: chess is clearly simpler for a machine.

This may surprise you, but it is worth looking at the features the two games have in common, as well as their differences – and of course, both have a great deal to do with our topic of artificial intelligence.

Common features

a) Clearly defined playing field

The chessboard has 64 black and white fields; only the pieces that are situated on these fields play a part. At cards, the bridge table could be regarded as a playing field, as could the so-called square “jass carpet” that is placed on a restaurant table; it is the material playing field in the same way that the material chessboard is for chess. If we are interested in successful playing behaviour, however, the colour of the jass carpet or the make of the chess board are immaterial; what counts is solely the abstract, i.e. “IT-type” of playing field: where can our chess pieces and playing cards move in a more mathematical way? And in this respect, the situation is completely clear at cards, too: the cards are in a clearly defined place at any given time, either in a player’s hand ready to be played, or in front of a player as a trick already won, or on the table as a face-up card to be seen by everyone. Both chess and cards can therefore be said to have a clearly defined playing field.

b) Clear rules

Here, too, there is hardly any difference between the two games. Although there are all sorts of variants of whist and bridge, and although jass rules differ from village to village and even from restaurant to restaurant (which may occasionally lead to heated discussions), as soon as a set of rules has been agreed upon, the situation is clear. As in chess, it is clear what goes and what doesn’t, and the players’ possible activities are clearly defined.

c) Clear course of play

Here again, the games do not differ from each other. At any point in time, there is precisely one player who is permitted to act, and his or her options are clearly defined.

d) Clear objective

Chess is about beating the opponent’s king; card games are about scoring points or tricks, depending on the variant. Games do not last an eternity. A card game is over when all the cards have been played; in chess, the draw and stalemate rules prevent a game from going on indefinitely. There is always one clear winner, there are always clear losers, and if need be there is a definitive tie.

Differences

e) Clear starting situation?

In chess, the starting situation is identical in every game; all pieces start at their appointed place. At cards, however, the pack of cards is shuffled before every game. Whereas in chess, we always start from precisely the same situation, we have to envisage a new one before every card game. Chance thus plays an important role in cards; in chess, it has been deliberately excluded. This is bound to have consequences. Since I have to factor in chance at cards, I cannot rely on certainties like in chess, but have to rely on probabilities.

f) Hidden information?

A lack of knowledge remains a challenge for card players throughout the game. Whereas in chess, everything is openly recognisable for each player on the board, card games literally thrive on players NOT knowing where the cards are. Therefore they must guess – i.e. rely on probabilities – and run certain risks. There is no guessing in chess; the situation is always clear, open and evident. Of course, this makes it substantially easier to describe the situation in chess; at cards, however, this lack of knowledge makes a description of the situation difficult.

g) Probabilities and emotions (psychology)

If I do not know everything, I have to rely on probabilities. Experience shows that this is something that we human beings are comprehensively very bad at. We let ourselves be guided by emotions much more strongly than we care to admit. Fears and hopes determine our expectations, and we often grossly misjudge probabilities. An AI program naturally has an edge over us in this respect since it does not have to cope with emotions and is much better at computing probabilities. Yet the machine wants to beat its opponent and will therefore have to assess its opponent’s reactions correctly. The AI program would therefore do well to take its opponent’s flawed handling of probabilities into its considerations, but this is not very easy in terms of algorithms. How does it recognise an optimist? Human players try to read their opponents while trying to mislead them about their own emotions at the same time. This is part of the game. It is no use to the program if it makes computations without any emotions while being incapable of recognising and assessing its opponent’s emotions.

h) Communication 

Chess is played by one player against the other. Card games usually involve four players playing each other in pairs. This aspect, i.e. that two individuals have to coordinate their actions, makes the game interesting, and it would be fatal for a card game program to neglect this aspect. But how should we program this? What has to be taken into account here, too, is point f) above, namely the fact that I cannot see my partner’s cards; I neither know my partner’s cards nor my opponents’. Of course my partner and I are interested in coordinating our game, and part of this is that we communicate our options (hidden cards) and our strategies (intentions for driving the game forward) to each other. If, for instance, I hold the ace of hearts, I would like my partner to lead hearts to enable me to win the trick. However, I am not allowed to tell him that openly – yet an experienced card player would not find this a problem. First of all, the run of the game often reveals who holds the ace of hearts. Of course it is not easy to discover this because both the cards that have already been played and possible tactics and strategies have to be taken into consideration. The number of options, the computation of the probabilities and the psychology of the players all come into play here, which can result in very exciting conflict situations – which ultimately also makes the game attractive. In chess, however, with its constantly very explicit situation, circumstances are a great deal simpler in this respect.

But this is not all:

i) The legal grey area

Is it really true that my partner and I are unable to exchange communication about our cards and strategies? Officially, of course, this is prohibited – but can this ban really be implemented in practice?

Of course it can’t. Whereas in chess, it is practically solely the explicit moves that play a part, there is a great deal of additional information at cards which a practised player must be able to read. How am I smiling when I’m playing a card? If I hold the ace of hearts, which can win the next trick, I obviously want my partner to help me and lead hearts. One possibility of achieving this in a jass game is to play a minor heart and place it on the table with distinctive emphasis. A practised partner will easily read this as a signal for him to lead hearts next time rather than diamonds to enable me to win the trick with my ace. No one will really be able to ban anyone from leading a card in a certain way, provided that this is done with sufficient discretion. Partners who are well attuned to each other do not only know the completely legal signals which they automatically emit through the selection of the cards they play, but also some signals from the grey area with which they coordinate their game.

These signals constitute information which an ambitious AI will have to be able to identify and process. The volume of information which it has to process for this purpose is not only much larger than the volume of information in chess, it is not limited by any manner of means either. My AI plays two human opponents, and those two also communicate with each other. The AI should be able to recognise their communication in order not to be hopelessly beaten. The signals agreed upon by the opponents may of course vary and be of any degree of sophistication. How can my AI discover what arrangements the two made prior to the game?

Conclusion

Card games are much more difficult to program than chess

If we want to develop a program for a card game, we will have to take into consideration aspects e) to i), which hardly play any part in chess. In terms of algorithms, however, aspects e) to i) constitute a difficult challenge owing to the imponderabilities.

In comparison with card games, chess is substantially less difficult for a computer because

– there is always the same starting situation,
– there is no hidden information,
– no probabilities need to be taken into account,
– human emotions play a small part,
– there is no legal grey area because no exchange of information between partners is possible.

For an AI program, chess is therefore the simpler game. It is completely defined, i.e. the volume of information that is in the game is very small, clearly disclosed and clearly limited. This is not the case with card games.

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This is a blog post about artificial intelligence. In the second part about games and intelligence, I will deal with Go and deep learning .

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Translation: Tony Häfliger and Vivien Blandford