title: Opting out against defection leads to stable coexistence with cooperation.
abstract: Cooperation coexisting with defection is a common phenomenon in nature and human society. Previous studies for promoting cooperation based on kin selection, direct and indirect reciprocity, graph selection and group selection have provided conditions that cooperators outcompete defectors. However, a simple mechanism of the long-term stable coexistence of cooperation and defection is still lacking. To reveal the effect of direct reciprocity on the coexistence of cooperation and defection, we conducted a simple experiment based on the Prisoner's Dilemma (PD) game, where the basic idea behind our experiment is that all players in a PD game should prefer a cooperator as an opponent. Our experimental and theoretical results show clearly that the strategies allowing opting out against defection are able to maintain this stable coexistence.
authors: Key Lab of Animal Ecology and Conservation Biology, Chinese Academy of Science, Beijing, China.|Laboratory of Mathematics and Complex Systems, Ministry of Education, School of Mathematical Sciences, Beijing Normal University, Beijing, China.
authors: Bo-Yu
authors: BY
authors: Zhang
authors: Key Lab of Animal Ecology and Conservation Biology, Chinese Academy of Science, Beijing, China.
authors: Song-Jia
authors: SJ
authors: Fan
authors: Key Lab of Animal Ecology and Conservation Biology, Chinese Academy of Science, Beijing, China.|Department of Mathematics and Statistics, University of Montreal, Montreal, Canada.
authors: Cong
authors: C
authors: Li
authors: Key Lab of Animal Ecology and Conservation Biology, Chinese Academy of Science, Beijing, China.
authors: Xiu-Deng
authors: XD
authors: Zheng
authors: School of Complex Systems, Beijing Normal University, Beijing, China.
authors: Jian-Zhang
authors: JZ
authors: Bao
authors: Department of Mathematics, Wilfrid Laurier University, Waterloo, Canada.
authors: Ross
authors: R
authors: Cressman
authors: Key Lab of Animal Ecology and Conservation Biology, Chinese Academy of Science, Beijing, China.
authors: Yi
authors: Y
authors: Tao