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1.
Heterogeneous aspirations promote cooperation in the prisoner's dilemma game
Matjaž Perc, Zhen Wang, 2010, original scientific article

Abstract: To be the fittest is central to proliferation in evolutionary games. Individuals thus adopt the strategies of better performing players in the hopeof successful reproduction. In structured populations the array of those that are eligible to act as strategy sources is bounded to the immediate neighbors of each individual. But which one of these strategy sources should potentially be copied? Previous research dealt with this question either by selecting the fittest or by selecting one player uniformly at random. Here we introduce a parameter that interpolates between these two extreme options. Setting equal to zero returns the random selection of the opponent, while positive favor the fitter players. In addition, we divide the population intotwo groups. Players from group select their opponents as dictated by the parameter , while players from group do so randomly irrespective of . We denote the fraction of players contained in groups and by and , respectively. The two parameters and allow us to analyze in detail how aspirations in the context of the prisoner's dilemma game influence the evolution of cooperation. We find that for sufficiently positive values of there exist a robust intermediate for which cooperation thrives best. The robustness of this observation is tested against different levels of uncertainty in the strategy adoption process and for different interaction networks. We also provide complete phase diagrams depicting the dependence of the impact of and for different values of , and contrast the validity of ourconclusions by means of an alternative model where individual aspiration levels are subject to evolution as well. Our study indicates that heterogeneity in aspirations may be key for the sustainability of cooperation in structured populations.
Keywords: evolutionary game theory, prisoner's dilemma, spatial games, aspirations, social systems, physics and society
Published: 19.06.2017; Views: 498; Downloads: 197
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2.
Uncertainties facilitate aggressive behavior in a spatial hawk-dove game
Matjaž Perc, 2007, original scientific article

Abstract: We study effects of additive spatiotemporal random variations, introduced to the payoffs of a spatial hawk-dove game, on the evolution of the reconciliatory and the aggressive strategy. We show that uncertainties facilitate aggressive behavior for a broad range of resource values. In particular, aggressors thrive best if stochastic influences are of the order of magnitude of deterministic payoff values. We argue that random payoff variations are potent and plausible promoters of aggressive behavior in human as well as animal societies if only the hawk-dove game payoff ranking applies.
Keywords: evolutionary game theory, hawk-dove game, noise, spatial games
Published: 31.05.2012; Views: 925; Downloads: 28
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Evolution of interactions and cooperation in the spatial prisoner's dilemma game
Chunyan Zhang, Jianlei Zhang, Guangming Xie, Long Wang, Matjaž Perc, 2011, original scientific article

Abstract: We study the evolution of cooperation in the spatial prisoner's dilemma game where players are allowed to establish new interactions with others. By employing a simple coevolutionary rule entailing only two crucial parameters, we find that different selection criteria for the new interaction partners as well as their number vitally affect the outcome of the game. The resolution of the social dilemma is most probable if the selection favors more successful players and if their maximally attainable number is restricted. While the preferential selection of the best players promotes cooperation irrespective of game parametrization, the optimal number of new interactions depends somewhat on the temptation to defect. Our findings reveal that the "making of new friends" may be an important activity for the successful evolution of cooperation, but also that partners must be selected carefully and their number limited.
Keywords: evolutionary games, prisoner's dilemma, coevolution, complex networks, friendship
Published: 19.06.2017; Views: 248; Downloads: 206
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5.
Evolutionary establishment of moral and double moral standards through spatial interactions
Dirk Helbing, Attila Szolnoki, Matjaž Perc, György Szabó, 2010, original scientific article

Abstract: Situations where individuals have to contribute to joint efforts or share scarce resources are ubiquitous. Yet, without proper mechanisms to ensure cooperation, the evolutionary pressure to maximize individual success tends to create a tragedy of the commons (such as over-fishing or the destruction of our environment). This contribution addresses a number of related puzzles of human behavior with an evolutionary game theoretical approach as it has been successfully used to explain the behavior of other biological species many times, from bacteria to vertebrates. Our agent-based model distinguishes individuals applying four different behavioral strategies: non-cooperative individuals ('defectors'), cooperative individuals abstaining from punishment efforts (called 'cooperators' or 'second-order free-riders'), cooperators who punish non-cooperative behavior ('moralists'), and defectors, who punish otherdefectors despite being non-cooperative themselves ('immoralists'). By considering spatial interactions with neighboring individuals, our model reveals several interesting effects: First, moralists can fully eliminate cooperators. This spreading of punishing behavior requires a segregation of behavioral strategies and solves the 'second-order free-rider problem'. Second, the system behavior changes its character significantly even after very long times ('who laughs last laughs best effect'). Third, the presence of a number of defectors can largely accelerate the victory of moralists over non-punishing cooperators. Fourth, in order to succeed, moralists may profit from immoralists in a way that appears like an 'unholy collaboration'. Our findings suggest that the consideration of punishment strategies allows one to understand the establishment and spreading of 'moral behavior' by means of game-theoretical concepts. This demonstrates that quantitative biological modeling approaches are powerful even in domains that have been addressed with non-mathematical concepts so far. The complex dynamics of certain social behaviors become understandable as the result of an evolutionary competition between different behavioral strategies.
Keywords: evolutionary game theory, social dilemmas, spatial games, moral, cooperation
Published: 16.06.2017; Views: 406; Downloads: 224
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6.
Coevolution of quantum and classical strategies on evolving random networks
Qiang Li, Azhar Iqbal, Matjaž Perc, Minyou Chen, Derek Abbott, 2013, original scientific article

Abstract: We study the coevolution of quantum and classical strategies on weighted and directed random networks in the realm of the prisoners dilemma game. During the evolution, agents can break and rewire their links with the aim of maximizing payoffs, and they can also adjust the weights to indicate preferences, either positive or negative, towards their neighbors. The network structure itself is thus also subject to evolution. Importantly, the directionality of links does not affect the accumulation of payoffs nor the strategy transfers, but serves only to designate the owner of each particular link and with it the right to adjust the link as needed. We show that quantum strategies outperform classical strategies, and that the critical temptation to defect at which cooperative behavior can be maintained rises, if the network structure is updated frequently. Punishing neighbors by reducing the weights of their links also plays an important role in maintaining cooperation under adverse conditions. We find that the self-organization of the initially random network structure, driven by the evolutionary competition between quantum and classical strategies, leads to the spontaneous emergence of small average path length and a large clustering coefficient.
Keywords: evolutionary games, quantum strategies, coevolution, random networks, cooperation
Published: 19.06.2017; Views: 338; Downloads: 184
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7.
Understanding recurrent crime as system-immanent collective behavior
Matjaž Perc, Karsten Donnay, Dirk Helbing, 2013, original scientific article

Abstract: Containing the spreading of crime is a major challenge for society. Yet, since thousands of years, no effective strategy has been found to overcome crime. To the contrary, empirical evidence shows that crime is recurrent, a fact that is not captured well by rational choice theories of crime. According to these, strong enough punishment should prevent crime from happening. To gain a better understanding of the relationship between crime and punishment, we consider that the latter requires prior discovery of illicit behavior and study a spatial version of the inspection game. Simulations reveal the spontaneous emergence of cyclic dominance between criminals, inspectors, and ordinary people as a consequence of spatial interactions. Such cycles dominate the evolutionary process, in particular when the temptation to commit crime or the cost of inspection are low or moderate. Yet, there are also critical parameter values beyond which cycles cease to exist and the population is dominated either by a stable mixture of criminals and inspectors or one of these two strategies alone. Both continuous and discontinuous phase transitions to different final states are possible, indicating that successful strategies to contain crime can be very much counter-intuitive and complex. Our results demonstrate that spatial interactions are crucial for the evolutionary outcome of the inspection game, and they also reveal why criminal behavior is likely to be recurrent rather than evolving towards an equilibrium with monotonous parameter dependencies.
Keywords: crime, evolutionary games, collective phenomena, phase transitions, statistical physics
Published: 19.06.2017; Views: 481; Downloads: 207
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8.
Defection and extortion as unexpected catalysts of unconditional cooperation in structured populations
Attila Szolnoki, Matjaž Perc, 2014, original scientific article

Abstract: We study the evolution of cooperation in the spatial prisoner%s dilemma game, where besides unconditional cooperation and defection, tit-for-tat, win-stay-lose-shift and extortion are the five competing strategies. While pairwise imitation fails to sustain unconditional cooperation and extortion regardless of game parametrization, myopic updating gives rise to the coexistence of all five strategies if the temptation to defect is sufficiently large or if the degree distribution of the interaction network is heterogeneous. This counterintuitive evolutionary outcome emerges as a result of an unexpected chain of strategy invasions. Firstly, defectors emerge and coarsen spontaneously among players adopting win-stay-lose-shift. Secondly, extortioners and players adopting tit-for-tat emerge and spread via neutral drift among the emerged defectors. And lastly, among the extortioners, cooperators become viable too. These recurrent evolutionary invasions yield a five-strategy phase that is stable irrespective of the system size and the structure of the interaction network, and they reveal the most unexpected mechanism that stabilizes extortion and cooperation in an evolutionary setting.
Keywords: social dilemma, evolutionary games, collective phenomena, phase transitions, physics of social systems
Published: 23.06.2017; Views: 255; Downloads: 191
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9.
Effects of adaptive degrees of trust on coevolution of quantum strategies on scale-free networks
Qiang Li, Minyou Chen, Matjaž Perc, Azhar Iqbal, Derek Abbott, 2013, original scientific article

Abstract: We study the impact of adaptive degrees of trust on the evolution of cooperation in the quantum prisoner's dilemma game. In addition to the strategies, links between players are also subject to evolution. Starting with a scale-free interaction network, players adjust trust towards their neighbors based on received payoffs. The latter governs the strategy adoption process, while trust governs the rewiring of links. As soon as the degree of trust towards a neighbor drops to zero, the link is rewired to another randomly chosen player within the network. We find that for small temptations to defect cooperators always dominate, while for intermediate and strong temptations a single quantum strategy is able to outperform all other strategies. In general, reciprocal trust remains within close relationships and favors the dominance of a single strategy. Due to coevolution, the power-law degree distributions transform to Poisson distributions.
Keywords: evolutionary games, quantum strategies, coevolution, random networks, cooperation, statistical physics of social systems
Published: 23.06.2017; Views: 235; Downloads: 185
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10.
Excessive abundance of common resources deters social responsibility
Xiaojie Chen, Matjaž Perc, 2014, original scientific article

Abstract: We study the evolution of cooperation in the collective-risk social dilemma game, where the risk is determined by a collective target that must be reached with individual contributions. All players initially receive endowments from the available amount of common resources. While cooperators contribute part of their endowment to the collective target, defectors do not. If the target is not reached, the endowments of all players are lost. In our model, we introduce a feedback between the amount of common resources and the contributions of cooperators. We show that cooperation can be sustained only if the common resources are preserved but never excessively abound. This, however, requires a delicate balance between the amount of common resources that initially exist, and the amount cooperators contribute to the collective target. Exceeding critical thresholds in either of the two amounts leads to loss of cooperation, and consequently to the depletion of common resources.
Keywords: social dilemma, evolutionary games, public goods, abundance, phase transitions, physics of social systems
Published: 23.06.2017; Views: 446; Downloads: 203
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