by Dr. S. Reisman
In computer play, the aggressive method of play is significantly better than the defensive. SIMULATED STRATEGIES OF GAME PLAYING by Dr. S. Reisman IBM Canada, Ltd. Laboratory Game theory enables one to classify competitive games according to characteristics of rules of play of the game. Consequently, the game of chess is described as a two-person, zero sum game of perfect information. This classification describes a competitive situation between two players in which the total game situation is open to observation to both players. Both players have opposite interests in the outcome and one player's win is the other's loss. in addition, the game can be terminated ln a finite number of moves. Games of perfect information differ from games of imperfect information by the fact that, in the latter, there is no best strategy. However, in the former, sometimes called strictly determined games, the player with the best strategy will win regardless of his opponent's play. The game of Draw and Match Dominoes is classified as a two-person, zero sum of Imperfect information and according to game theory there is no best strategy of play which can be employed. It was hypothesized while this might in fact be true, techniques of simulating cognitive processes might be used to determine if better strategies do exist. Consequently, player protocols were gathered from opponents while they played a simplified version of Draw and Match Dominoes. An analysls of the protocols indicated that human players use a combination of a number of components of play to form their playing strategy. These components are described as: (1) the defensive component; (2) the aggressive component; and, (3) the statistical component. The defensive component is characterized by a player's being more apt to make assumptions about his opponent's game situation and as a result attempting to block his every move. The aggressive component is different in that the player using it makes no assumptions about his opponent's situation and instead makes his move only on the basis of his own known situation with the objective of playing his longest chain of tiles. The statistical component is used rarely, and only as a last means of decision making if the other two components are unsatisfactory. It is characterized by the pIayer's counting the various tiles already played and making decisions as to the likelihood of matches being drawn from the bank. In an effort to determine the validity of this classification system an interactive Dominoes-playing program was written in the list processing language IPL-V." The program was altered so that the strategy employed in a game could be varied to combinations of the above components. Results of the computer play indicated that the classification system is, in fact, an operational one. In order to determine if there are optimal strategies of play, the interactive program was altered to allow the play of the game to be between two computer programs rather than between a human and a computer, as in the original version. In this way, one program using one type of strategy could be played against a program of another strategy. The programs were each loaded onto a different interactive terminal and the output of one terminal's program was used as input to the terminal' with the second player-program. In this attempt to determine a better strategy, one program was set to use only the defensive component, and the other, only the aggressive component. The results of a number of games played in this manner indicate that the aggressive component of play is significantly better than the defensive component. An analysis of the games played indicated the reasons for this. The strictly defensive player makes assumptions concerning his opponent's situation while ignoring his own game situation and the harm he may be doing to himself by blindly attacking his opponent. The typical human player does not rely on only one component of play, but both makes assumptions about his opponent and considers his own situation. For this reason, a better strategy would probably consist of a combination of these components in a particular game situation. Although the search for a better strategy of play in the game of Dominoes is not of earth-shaking importance, the potential spinoff of the techniques used and results obtained may be of value in other situations of a competitive nature. 'For a complete description see: Dominoes-A Computer Simulation of Cognitive Processes, Simulation and Games, Vol. 3, No. 2, pp. 155-164.