The choice behavior in 2-Alternative N-Person homogeneous games was exhaustively investigated using a questionnaire method.
Two complete sets of 39 games, the one set was based on linear payoff functions (L condition), and the other on two-interval step-wise payoff functions Scondition, were chosen on the basis of a game classification method developed by Takigawa (1989).
The 39 games all for 11 players were defined respectively by the combinations of each level of four endpoints of payoff functions. Each of the 39 games was made identifiable by 4 alphabets representing the level of the endpoint (A>B>C>D). For example, the N-Person Prisoner's Dilemma game is coded DBCA. The subjects participated consisted of 132 college students, each of whom was assigned randomly to either of the two conditions. Table 3 shows the choice distributions and the degree of difficulties rated by the subjects on a 7-point scale. There was little difference between the 2 conditions in the choice distributions and the degree of difficulties. An efficiency factor was calculated for each game in order to evaluate the subjects' choice in terms of collective payoff. Figs. 1 and 2 show the two dimensional distributions of the 39 games in each condition, where the ordinate denotes the efficiency and the abscissa the experienced degree of difficulty. Based on the obtained two dimensional distributions, each game was classified into one of the 4 categories, highdifficulty high-efficiency, high-difficulty lowefficiency, low-difficulty high-efficiency, and lowdifficulty lowefficiency categories. Some noteworthy non-trivial games such as BBBA, CABA, CBAD, and CBCA were found in addition to N-Person PD (DBCA). Seven decision motives were extracted from the reasons given by subjects for their choice of alternatives in each game. The extracted motives were: type of alternative, maximax, minimax, collective payoff, α comparison, β comparison, and maximization of difference. Table 4 shows the alternatives in each game chosen by each of the 7 motives.
The types of dilemmas, the equivalent and the exclusive, can be discriminated in the framework of the decision motive model. The relations between the types of dilemmas and the conflict situations were also analyzed. Finally, some methodological problems in the experimental game studies were discussed.