1. Correlation of positive and negative reciprocity fails to confer an evolutionary advantage: phase transitions to elementary strategiesAttila Szolnoki, Matjaž Perc, 2013, izvirni znanstveni članek Opis: Economic experiments reveal that humans value cooperation and fairness. Punishing unfair behavioris therefore common, and according to the theory of strong reciprocity, it is also directly related to rewarding cooperative behavior. However, empirical data fail to confirm that positive and negative reciprocity are correlated. Inspired by this disagreement, we determine whether the combined application of reward and punishment is evolutionarily advantageous. We study a spatial public goods game, where in addition to the three elementary strategies of defection, rewarding, and punishment, a fourth strategy that combines the latter two competes for space. We find rich dynamical behavior that gives rise to intricate phase diagrams where continuous and discontinuous phase transitions occur in succession. Indirect territorial competition, spontaneous emergence of cyclic dominance, as well as divergent fluctuations of oscillations that terminate in an absorbing phase are observed. Yet, despite the high complexity of solutions, the combined strategy can survive only in very narrow and unrealistic parameter regions. Elementary strategies, either in pure or mixed phases, are much more common and likely to prevail. Our results highlight the importance of patterns and structure in human cooperation, which should be considered in future experiments.
Ključne besede: public goods, punishment, reward, evolutionary games, collective phenomena, phase transitions, physics of social systems
Objavljeno v DKUM: 03.08.2017; Ogledov: 1007; Prenosov: 345
 Celotno besedilo (667,46 KB)
Gradivo ima več datotek! Več... |
2. Vortices determine the dynamics of biodiversity in cyclical interactions with protection spilloversAttila Szolnoki, Matjaž Perc, 2015, izvirni znanstveni članek Opis: If rock beats scissors and scissors beat paper, one might assume that rock beats paper too. But this is not the case for intransitive relationships that make up the famous rock-paper-scissors game. However, the sole presence of paper might prevent rock from beating scissors, simply because paper beats rock. This is the blueprint for the rock-paper-scissors game with protection spillovers, which has recently been introduced as a new paradigm for biodiversity in well-mixed microbial populations. Here we study the game in structured populations, demonstrating that protection spillovers give rise to spatial patterns that are impossible to observe in the classical rock-paper-scissors game.Weshow that the spatiotemporal dynamics of the system is determined by the density of stable vortices, which may ultimately transform to frozen states, to propagating waves, or to target waves with reversed propagation direction, depending further on the degree and type of randomness in the interactions among the species. If vortices are rare, the fixation to waves and complex oscillatory solutions is likelier. Moreover, annealed randomness in interactions favors the emergence of target waves, while quenched randomness favors collective synchronization. Our results demonstrate that protection spillovers may fundamentally change the dynamics of cyclic dominance in structured populations, and they outline the possibility of programming pattern formation in microbial populations.
Ključne besede: cyclical interactions, pattern formation, vortices, phase transitions, selforganization, biodiversity
Objavljeno v DKUM: 03.07.2017; Ogledov: 989; Prenosov: 392
Celotno besedilo (1,32 MB)
Gradivo ima več datotek! Več... |
3. Self-organization towards optimally interdependent networks by means of coevolutionZhen Wang, Attila Szolnoki, Matjaž Perc, 2014, izvirni znanstveni članek Opis: Coevolution between strategy and network structure is established as a means to arrive at the optimal conditions needed to resolve social dilemmas. Yet recent research has highlighted that the interdependence between networks may be just as important as the structure of an individual network. We therefore introduce the coevolution of strategy and network interdependence to see whether this can give rise to elevated levels of cooperation in the prisonerʼs dilemma game. We show that the interdependence between networks self-organizes so as to yield optimal conditions for the evolution of cooperation. Even under extremely adverse conditions, cooperators can prevail where on isolated networks they would perish. This is due to the spontaneous emergence of a two-class society, with only the upper class being allowed to control and take advantage of the interdependence. Spatial patterns reveal that cooperators, once arriving at the upper class, are much more competent than defectors in sustaining compact clusters of followers. Indeed, the asymmetric exploitation of interdependence confers to them a strong evolutionary advantage that may resolve even the toughest of social dilemmas.
Ključne besede: coevolution, cooperation, interdependent networks, evolutionary games, collective phenomena, self-organization, phase transitions, physics of social systems
Objavljeno v DKUM: 03.07.2017; Ogledov: 1098; Prenosov: 389
Celotno besedilo (887,51 KB)
Gradivo ima več datotek! Več... |
4. Self-organization of punishment in structured populationsMatjaž Perc, Attila Szolnoki, 2012, izvirni znanstveni članek Opis: Cooperation is crucial for the remarkable evolutionary success of the human species. Not surprisingly, some individuals are willing to bear additional costs in order to punish defectors. Current models assume that, once set, the fine and cost of punishment do not change over time. Here we show that relaxing this assumption by allowing players to adapt their sanctioning efforts in dependence on the success of cooperation can explain both the spontaneous emergence of punishment and its ability to deter defectors and those unwilling to punish them with globally negligible investments. By means of phase diagrams and the analysis of emerging spatial patterns, we demonstrate that adaptive punishment promotes public cooperation through the invigoration of spatial reciprocity, the prevention of the emergence of cyclic dominance, or the provision of competitive advantages to those that sanction antisocial behavior. The results presented indicate that the process of self-organization significantly elevates the effectiveness of punishment, and they reveal new mechanisms by means of which this fascinating and widespread social behavior could have evolved.
Ključne besede: cooperation, public goods, punishment, phase transitions, physics of social systems
Objavljeno v DKUM: 03.07.2017; Ogledov: 989; Prenosov: 401
Celotno besedilo (1,22 MB)
Gradivo ima več datotek! Več... |
5. Evolutionary advantages of adaptive rewardingAttila Szolnoki, Matjaž Perc, 2012, izvirni znanstveni članek Opis: Our well-being depends on both our personal success and the success of our society. The realization of this fact makes cooperation an essential trait. Experiments have shown that rewards can elevate our readiness to cooperate, but since giving a reward inevitably entails paying a cost for it, the emergence and stability of such behavior remains elusive. Here we show that allowing for the act of rewarding to self-organize in dependence on the success of cooperation creates several evolutionary advantages that instill new ways through which collaborative efforts are promoted. Ranging from indirect territorial battle to the spontaneous emergence and destruction of coexistence, phase diagrams and the underlying spatial patterns reveal fascinatingly rich social dynamics that explain why this costly behavior has evolved and persevered. Comparisons with adaptive punishment, however, uncover an Achilles heel of adaptive rewarding, coming from over-aggression, which in turn hinders optimal utilization of network reciprocity. This may explain why, despite its success, rewarding is not as firmly embedded into our societal organization as punishment.
Ključne besede: cooperation, public goods, reward, punishment, phase transitions, physics of social systems
Objavljeno v DKUM: 30.06.2017; Ogledov: 1372; Prenosov: 391
Celotno besedilo (2,15 MB)
Gradivo ima več datotek! Več... |
6. Wisdom of groups promotes cooperation in evolutionary social dilemmasAttila Szolnoki, Zhen Wang, Matjaž Perc, 2012, izvirni znanstveni članek Opis: Whether or not to change strategy depends not only on the personal success of each individual, but also on the success of others. Using this as motivation, we study the evolution of cooperation in games that describe social dilemmas, where the propensity to adopt a different strategy depends both on individual fitness as well as on the strategies of neighbors. Regardless of whether the evolutionary process is governed by pairwise or group interactions, we show that plugging into the wisdom of groups strongly promotes cooperative behavior. The more the wider knowledge is taken into account the more the evolution of defectors is impaired. We explain this by revealing a dynamically decelerated invasion process, by means of which interfaces separating different domains remain smooth and defectors therefore become unable to efficiently invade cooperators. This in turn invigorates spatial reciprocity and establishes decentralized decision making as very beneficial for resolving social dilemmas.
Ključne besede: cooperation, public goods, wisdom of crowds, phase transitions, physics of social systems
Objavljeno v DKUM: 23.06.2017; Ogledov: 1158; Prenosov: 377
Celotno besedilo (646,99 KB)
Gradivo ima več datotek! Več... |
7. Sustainable institutionalized punishment requires elimination of second-order free-ridersMatjaž Perc, 2012, izvirni znanstveni članek Opis: Although empirical and theoretical studies affirm that punishment can elevate collaborative efforts, its emergence and stability remain elusive. By peer-punishment the sanctioning is something an individual elects to do depending on the strategies in its neighborhood. The consequences of unsustainable efforts are therefore local. By pool-punishment, on the other hand, where resources for sanctioning are committed in advance and at large, the notion of sustainability has greater significance. In a population with free-riders, punishers must be strong in numbers to keep the "punishment pool" from emptying. Failure to do so renders the concept of institutionalized sanctioning futile. We show that pool-punishment in structured populations is sustainable, but only if second-order free-riders are sanctioned as well, and to a such degree that they cannot prevail. A discontinuous phase transition leads to an outbreak of sustainability when punishers subvert second-order free-riders in the competition against defectors.
Ključne besede: cooperation, public goods, punishment, institutions, phase transitions, physics of social systems
Objavljeno v DKUM: 23.06.2017; Ogledov: 1222; Prenosov: 351
Celotno besedilo (469,23 KB)
Gradivo ima več datotek! Več... |
8. If players are sparse social dilemmas are too: importance of percolation for evolution of cooperationZhen Wang, Attila Szolnoki, Matjaž Perc, 2012, izvirni znanstveni članek Opis: Spatial reciprocity is a well known tour de force of cooperation promotion. A thorough understanding of the effects of different population densities is therefore crucial. Here we study the evolution of cooperation in social dilemmas on different interaction graphs with a certain fraction of vacant nodes. We find that sparsity may favor the resolution of social dilemmas, especially if the population density is close to the percolation threshold of the underlying graph. Regardless of the type of the governing social dilemma as well as particularities of the interaction graph, we show that under pairwise imitation the percolation threshold is a universal indicator of how dense the occupancy ought to be for cooperation to be optimally promoted. We also demonstrate that myopic updating, due to the lack of efficient spread of information via imitation, renders the reported mechanism dysfunctional, which in turn further strengthens its foundations.
Ključne besede: cooperation, public goods, punishment, phase transitions, physics of social systems
Objavljeno v DKUM: 23.06.2017; Ogledov: 1039; Prenosov: 355
Celotno besedilo (413,53 KB)
Gradivo ima več datotek! Več... |
9. Excessive abundance of common resources deters social responsibilityXiaojie Chen, Matjaž Perc, 2014, izvirni znanstveni članek Opis: 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.
Ključne besede: social dilemma, evolutionary games, public goods, abundance, phase transitions, physics of social systems
Objavljeno v DKUM: 23.06.2017; Ogledov: 1688; Prenosov: 385
Celotno besedilo (950,12 KB)
Gradivo ima več datotek! Več... |
10. Directional learning and the provisioning of public goodsHeinrich H. Nax, Matjaž Perc, 2015, izvirni znanstveni članek Opis: We consider an environment where players are involved in a public goods game and must decide repeatedly whether to make an individual contribution or not. However, players lack strategically relevant information about the game and about the other players in the population. The resulting behavior of players is completely uncoupled from such information, and the individual strategy adjustment dynamics are driven only by reinforcement feedbacks from each player's own past. We show that the resulting "directional learning" is sufficient to explain cooperative deviations away from the Nash equilibrium. We introduce the concept of k-strong equilibria, which nest both the Nash equilibrium and the Aumann-strong equilibrium as two special cases, and we show that, together with the parameters of the learning model, the maximal k-strength of equilibrium determines the stationary distribution. The provisioning of public goods can be secured even under adverse conditions, as long as players are sufficiently responsive to the changes in their own payoffs and adjust their actions accordingly. Substantial levels of public cooperation can thus be explained without arguments involving selflessness or social preferences, solely on the basis of uncoordinated directional (mis)learning.
Ključne besede: cooperation, public goods, directional learning, phase transitions, physics of social systems
Objavljeno v DKUM: 23.06.2017; Ogledov: 883; Prenosov: 331
Celotno besedilo (1,40 MB)
Gradivo ima več datotek! Več... |
