Comparing question answering strategies for Cluedo

The game of Cluedo – also known as Clue – requires working out a ‘murder’ scene by elimination. Beginners typically rely only on cards in their hand and cards they have seen; experts also use propositional logic about cards they have not seen, based on questions asked and answers given. A game-playing program has been written to test the value of using deductions to guide question-asking. This paper describes how the program has been designed and presents results for five strategies (including a ‘no intelligence’ strategy) for three player games and six player games. The program has been written using JESS (the Java Expert System Shell). The results were not quite as expected. Using propositional logic did indeed allow the game to be solved in fewer turns, but there were times when adding extra information to the logical deductions made things worse, not better. There is also a strong effect from the mechanics of the game – specifically, which room is chosen as the ‘guilty’ location – on the number of turns required to solve the problem. It is suggested that strategies might benefit from occasionally breaking away from their highly focussed approach to inject variety into the questioning The test cases used are listed in an appendix.