Social Cycling and Conditional Responses in the Rock-Paper-Scissors Game (http://www.nature.com/srep/2014/140725/srep05830/full/srep05830.html）is the findings of a research jointly conducted by Wang Zhijian and Professor Xu Bin of the Experimental Social Science Laboratory (ESSL) of Zhejiang University and Zhou Haijun of the Institute of Theoretical Physics of the Chinese Academy of Sciences. It was selected as “the science news highlights of 2014” (http://www.bbc.com/news/science-environment-30132560) by BBC News on December 25 and the "Best of 2014" (http://www.technologyreview.com/views/)by MIT Technology Review on December 24. Approximately 50 scientific research findings have been selected in the MIT annual review in the past 5 years, among which only 2 come from China.
The research uses experimental economics methods to study the fundamental model system of Rock-Paper-Scissors (RPS) game, classic game theory of infinite rationality predicts the Nash equilibrium (NE) state with every player randomizing her choices to avoid being exploited, while evolutionary game theory of bounded rationality in general predicts persistent cyclic motions, especially for finite populations. The “Rock-paper-Scissors” research group recruited a total of 360 students from different disciplines at Zhejiang University to form 60 disjoint populations of size N=6. Each population then carried out one experimental session by playing the RPS game 300 rounds.
Researchers observe population-level cyclic motions in a laboratory experiment of the discrete-time iterated RPS game under the traditional random pairwise-matching protocol. This collective behavior contradicts with the NE theory but it is quantitatively explained by a microscopic model of win-lose-tie conditional response without any adjustable parameter.
The theoretical calculations reveal that this new strategy may offer higher payoffs to individual players in comparison with the NE mixed strategy, suggesting that high social efficiency is achievable through optimized conditional response.
This cross-disciplinary research was initiated in December 2012. The relevant paper was officially published in Scientific Reports, an online open access scientific mega journal published by the Nature Publishing Group, on July 25, 2014.
On April 30, 2014, MIT Technology Review recommended this research in an article entitled How to Win at Rock-Paper-Scissors. It claimed that the first large-scale measurements of the way humans play Rock-Paper-Scissors revealed a hidden pattern of play that opponents can exploit to gain a vital edge. On May 2, 2014, BBC also reported this research. Since then, there has been wide follow-up coverage in 100-plus news media and specialized websites in natural philosophy, math, psychology and physics. The findings of this research have been the main topic in many seminars and workshops both at home and abroad. They have also been part of the curriculum in game theory, microeconomics, optimization algorism and theory, and computer sciences.
As early as June 15, 2013, Evidences of Cycles in Rock-Paper-Scissors-Dumb Experimental Games (http://arxiv.org/abs/1306.2250v1) by Wang Zhijian was included as an interesting arXiv paper in MIT Technology Review. These work, together with Periodic frequencies of the cycles in 2 x 2 games: evidence from experimental economics (https://advanceseng.com/applied-physics/periodic-frequencies-cycles-2-x-2-games-evidence-experimental-economics/), the peer-reviewed paper which is a production of matching pennies in game dynamics and published in The European Physical Journal B (EPJB) in February 2014 and later featured in Advances in Engineering(0.1% are selected), are part of progressive achievements of ESSL in fundamental research of game theory.
Chinese Editor: Hangchun Li, Jun Huang