CompleX Lab, Web Sciences Center, University of Electronic Science and Technology of China, Chengdu 611731, China.
Big Data Research Center, University of Electronic Science and Technology of China, Chengdu 611731, China.
Phys Rev E. 2017 May;95(5-1):052302. doi: 10.1103/PhysRevE.95.052302. Epub 2017 May 1.
In this paper, we study the evolution of cooperation in structured populations (individuals are located on either a regular lattice or a scale-free network) in the context of repeated games by involving three types of strategies, namely, unconditional cooperation, unconditional defection, and extortion. The strategy updating of the players is ruled by the replicator-like dynamics. We find that extortion strategies can act as catalysts to promote the emergence of cooperation in structured populations via different mechanisms. Specifically, on regular lattice, extortioners behave as both a shield, which can enwrap cooperators inside and keep them away from defectors, and a spear, which can defeat those surrounding defectors with the help of the neighboring cooperators. Particularly, the enhancement of cooperation displays a resonance-like behavior, suggesting the existence of optimal extortion strength mostly favoring the evolution of cooperation, which is in good agreement with the predictions from the generalized mean-field approximation theory. On scale-free network, the hubs, who are likely occupied by extortioners or defectors at the very beginning, are then prone to be conquered by cooperators on small-degree nodes as time elapses, thus establishing a bottom-up mechanism for the emergence and maintenance of cooperation.
在本文中，我们研究了在重复博弈的背景下，结构种群（个体位于规则晶格或无标度网络上）中合作的演化，涉及三种策略，即无条件合作、无条件背叛和敲诈。玩家的策略更新由类似复制者的动力学规则决定。我们发现，敲诈策略可以通过不同的机制充当促进结构种群中合作出现的催化剂。具体来说，在规则晶格上，敲诈者既可以作为盾牌，将合作者包裹在内，使其远离背叛者，也可以作为长矛，在相邻合作者的帮助下击败周围的背叛者。特别地，合作的增强显示出共振样的行为，表明存在最优的敲诈强度，这主要有利于合作的进化，这与广义平均场近似理论的预测一致。在无标度网络上，最初处于敲诈者或背叛者占据优势的枢纽节点，随着时间的推移，更容易被小度数节点上的合作者所征服，从而建立了合作出现和维持的自下而上的机制。
