Ki Baek RIKEN Center for Computational Science, Japan Pukyong National University, Korea YM and S.K. Baek "Friendly-rivalry solution to the iterated n-person public-goods game" Plos. Comp. Biol. (2021)
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other's fragile against an error It cannot exploit naive cooperator. History Next move C,C C C,D D D,C C D,D D Tit-for-Tat c c c c d d c c d d c c TFT c c c c d d c c d d c c TFT TFT c c c c c c TFT AllC c c c c c c Win-Stay-Lose-Shift History Next move C,C C C,D D D,C D D,D C tolerant against an error It can exploit naive cooperator. weak against defectors c c d d c d d WSLS AllD d d d d d c c c d d c c c WSLS AllC d d c c c c c c d c c d d c c WSLS WSLS c
Friendly rivals form a cooperative Nash equilibrium with a guarantee that you'll never lose. ⌦ Rival The long-term payoff is never outperformed by any kind of co-player. ⌦ ⌦ cooperation Partner When both players use the strategy, they maintain cooperation with probability 1 as e -> 0.
Memory-1 strategies: 16 • => no strategies satisfies the criteria • # of Memory-2 strategies: 2^16 = 65536 • A friendly rival TFT-ATFT was found. Yi et al., J. Theor. Biol. (2017) It is impossible to generalize TFT-ATFT to n-players game.
strategies: 2^8 • # of Memory-2 strategies: 2^40 • => No friendly rivals was found. • # of Memory-3 strategies: 2^288 • => There are at least 256 friendly rivals. Y Murase & S.K. Baek J. Theor. Biol. (2018)
bound TFT-ATFT solution for n=3 m=1 : 256 m=2 : 65,536 m=3 : 18,446,744,073,709,551,616 222m <latexit sha1_base64="SnIU+E5cPeQhQyyV4MGmqG9JhrI=">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</latexit> Yi et al., JTB (2017) → 4 friendly rivals → 0 friendly rivals # of memory-m strategies: → 4,261,844,305,281 friendly rivals most of them are so complicated strategies
c c c c c c c CAPRI CAPRI c c c c Recover cooperation when someone cooperated. c c c c CAPRI c c d d d d d c memory-3 strategy described by the five rules In all the other cases, defect. d d d d CAPRI d d d d d d d d Accept punishment when you made a mistake. c c c c d c c d c c CAPRI CAPRI c c accept punishment Punish co-player and then forgive him. conduct punishment
Prisoner's Dilemma and n-players' public goods game. • We found CAPRI-n that is described by five simple rules. In various respects, it is one of the best strategies ever. • cooperation is robust against error (partner) • never allows any co-player to outperform you (rivalry) • evolutionary robust for any environmental conditions • exploit a broad range of strategies (gTFT, WSLS) • not only for PD but for stag-hunt game and snow-drift game
the tragedy of the commons” Journal of Theoretical Biology, 449, 94-102 (2018) • Yohsuke Murase, Seung Ki Baek “Automata representation of successful strategies for social dilemmas” Scientific Reports, 10, 13370 (2020) • Yohsuke Murase, Seung Ki Baek “Five rules for friendly rivalry in direct reciprocity” Scientific Reports, 10, 16904 (2020) • Yohsuke Murase, Seung Ki Baek “Friendly-rivalry solution to the iterated n-person public- goods game” Plos Computational Biology, 17(1): e1008217 (2021) • Yohsuke Murase, Seung Ki Baek “Friendly-rivalry solutions for direct reciprocity” Proceedings of the ALIFE 2021: The 2021 Conference on Artificial Life. ALIFE 2021: The 2021 Conference on Artificial Life. Online. (pp. 68). ASME. (2021)