Frank Morgan R, Obradovich Nick, Sun Lijun, Woon Wei Lee, LeVeck Brad L, Rahwan Iyad
Media Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Belfer Center for Science and International Affairs, Kennedy School of Government, Harvard University, Cambridge, MA 02138, USA.
Sci Adv. 2018 Jan 3;4(1):eaao5348. doi: 10.1126/sciadv.aao5348. eCollection 2018 Jan.
Reciprocity stabilizes cooperation from the level of microbes all the way up to humans interacting in small groups, but does reciprocity also underlie stable cooperation between larger human agglomerations, such as nation states? Famously, evolutionary models show that reciprocity could emerge as a widespread strategy for achieving international cooperation. However, existing studies have only detected reciprocity-driven cooperation in a small number of country pairs. We apply a new method for detecting mutual influence in dynamical systems to a new large-scale data set that records state interactions with high temporal resolution. Doing so, we detect reciprocity between many country pairs in the international system and find that these reciprocating country pairs exhibit qualitatively different cooperative dynamics when compared to nonreciprocating pairs. Consistent with evolutionary theories of cooperation, reciprocating country pairs exhibit higher levels of stable cooperation and are more likely to punish instances of noncooperation. However, countries in reciprocity-based relationships are also quicker to forgive single acts of noncooperation by eventually returning to previous levels of mutual cooperation. By contrast, nonreciprocating pairs are more likely to exploit each other's cooperation via higher rates of defection. Together, these findings provide the strongest evidence to date that reciprocity is a widespread mechanism for achieving international cooperation.
互惠原则从微生物层面一直到小群体中互动的人类，都能稳定合作。那么，互惠原则是否也是诸如民族国家等更大规模人类群体之间稳定合作的基础呢？众所周知，进化模型表明，互惠原则可能会成为实现国际合作的一种广泛策略。然而，现有研究仅在少数国家对中发现了由互惠驱动的合作。我们将一种用于检测动态系统中相互影响的新方法应用于一个新的大规模数据集，该数据集以高时间分辨率记录国家间的互动。通过这样做，我们在国际体系中检测到许多国家对之间存在互惠现象，并发现与非互惠国家对相比，这些互惠国家对展现出性质不同的合作动态。与合作的进化理论一致，互惠国家对表现出更高水平的稳定合作，并且更有可能惩罚不合作行为。然而，处于基于互惠关系中的国家也会更快地原谅单次不合作行为，最终恢复到之前的相互合作水平。相比之下，非互惠国家对更有可能通过更高的背叛率来利用对方的合作。总之，这些发现提供了迄今为止最有力的证据，表明互惠是实现国际合作的一种广泛机制。
