Cooperation, but No Reciprocity: Individual Strategies in the Repeated Prisoner's Dilemma

• 成果类型: Article
• 署名作者: Breitmoser, Yves
• 署名单位: Humboldt University of Berlin
• 刊物名称: AMERICAN ECONOMIC REVIEW
• ISSN/ISSBN: 0002-8282
• DOI: 10.1257/aer.20130675
• 发表日期: 2015
• 页码: 2882-2910
• 关键词: tit-for-tat; repeated games; folk theorem; EFFECTIVE CHOICE; players models; WIN-STAY; equilibrium; BEHAVIOR; trust; STABILITY

摘要

In the repeated prisoner's dilemma, predictions are notoriously difficult. Recently, however, Blonski, Ockenfels, and Spagnolo (2011)-henceforth, BOS-showed that experimental subjects predictably cooperate when the discount factor exceeds a particular threshold. I analyze individual strategies in four recent experiments to examine whether strategies are predictable, too. Behavior is well summarized by Semi-Grim strategies: cooperate after mutual cooperation, defect after mutual defection, randomize otherwise. This holds both in aggregate and individually, and it explains the BOS-threshold: Semi-Grim equilibria appear as the discount factor crosses this threshold, and then, subjects start cooperating in round 1 and switch to Semi-Grim in continuation play.