2000 年 31 巻 3 号 p. 177-190
Generally, it is a difficult problem to adjust different claims of different interested parties in the process of large-scale and long-term infrastructure development project. Various parties are often in a social conflict with each other concerning their gain and loss that are brought about by the project. Such a social conflict is sometimes observed in a water resource development project that aims at construction of a dam, a river mouth weir, a reservoir, an irrigation canal and so on.
Game theory is instrumental to analyze a social conflict to predict possible consequences and furthermore to suggest rational solutions for each interested party that is referred to as a player in the theory. It is assumed in the game theory that each player has one or more options to be taken and each possible consequence is a unique combination of options each player has taken. Among possible consequences, special attention should be paid to equilibrium solutions, that is, a consequence in which each player could only expect decrease of gain even by altering its own option alone unless other players would change their options.
The present study depends on a game-theoretical method called conflict analysis that will be introduced in details later. At the same time, the study focuses on a dynamical aspect, that is, longitudinal change of psychological attitude each player has toward the project. The aspect has not been successfully taken into consideration in the game-theoretical perspective so far. Actually, it is often that each player changes its attitude during the long-term project. For example, an initial plan of a project that was once assumed rational for each player and thus also rational for a group of residents living near the project site and participating in the conflict as a player sometimes becomes irrational for the residents because of their change of attitude that has been caused by the passage of time, social influence of other players, environmental changes in the site and so on.
The present study develops a behavioral decision model to formulate the change of attitude of each player by a set of differential equations. In the model, two important assumptions are set. First assumption is that a player goes back and forth between two states with some probability. In one of states, a player remembers an event that triggered the project, a natural disaster in many cases, and in another, a player forgets the event. Second assumption is that each player's attitude tends to be affected by the options that were taken by the other players.