On strategic behaviors and prevention rules in participatory group decision processes

Participatory methods are employed for community and urban planning processes in order to involve the stakeholders and to reflect their opinions in the plans. However, the processes to obtain group decisions almost mandatorily contain conflicts of interests among the participants. In order to achieve final group decision which is preferable for more participants as much as possible, group decision support systems are used. This study focuses on the debate which is commonly used in group decision situations. Debates are expected to help intensive discussions among participants, and to make discussions more progressive because of the allocation of roles among participants. There is, however, risk that because of the allocation of limited roles the final decision can be maneuvered by some participants who has been allocated an eventual crucial role. The effects of two specific rules in debates to prevent maneuver, namely, `change of roles´ and `block of opinions´ are analyzed using game-theoretic debate models. It is shown that the combination of these rules can improve the welfare of the group.