Tipping Versus Cooperating To Supply A Public Good

In some important multiplayer situations, such as efforts to supply a global public good, players can
choose the game they want to play. In this paper we conduct an experimental test of the decision by a
group with fixed membership, playing over a finite number of periods, to choose between a “tipping”
game, in which every player wants to contribute to the public good provided enough other players
contribute, and a prisoners’ dilemma, the classic cooperation game. In the prisoners’ dilemma, the
first best outcome is attainable, but cannot be sustained as a Nash equilibrium. In the tipping game,
only a second best outcome may be attainable, but there exists a Nash equilibrium that is strictly
preferred to the one in the prisoners’ dilemma. We show that many groups persistently choose the
prisoners’ dilemma despite its strategic disadvantage, and that the groups that eventually choose
the tipping game do better than the ones that stick with the prisoners’ dilemma.

在一些重要的多人博弈情境中（例如全球公共物品的供给），参与者可自主选择其参与的博弈类型。本文针对固定成员组在有限周期内的决策行为开展实验研究，考察其在两类博弈间的选择：一类是临界点博弈（tipping game）——当足够多其他参与者贡献时，每个参与者均愿意为公共物品提供贡献；另一类是经典合作博弈——囚徒困境（prisoners’ dilemma）。在囚徒困境中，最优结果虽可实现，却无法作为纳什均衡（Nash equilibrium）维持；而在临界点博弈中，仅次优结果可能达成，但存在一个严格优于囚徒困境中纳什均衡的均衡状态。研究发现，尽管囚徒困境存在战略劣势，仍有大量组群持续选择该博弈；而最终选择临界点博弈的组群，其表现优于坚持囚徒困境的组群。