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Self-organization of punishment in structured populations
Matjaž 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: 03.07.2017; Ogledov: 35; Prenosov: 1
.pdf Polno besedilo (1,22 MB)

Punish, but not too hard: how costly punishment spreads in the spatial public goods game
Dirk Helbing, Attila Szolnoki, Matjaž Perc, György Szabó, 2010, izvirni znanstveni članek

Opis: We study the evolution of cooperation in spatial public goods games where, besides the classical strategies of cooperation (C) and defection (D), we consider punishing cooperators (PC) or punishing defectors (PD) as an additional strategy. Using a minimalist modeling approach, our goal is to separately clarify and identify the consequences of the two punishing strategies. Since punishment is costly, punishing strategies lose the evolutionary competition in case of well-mixed interactions. When spatial interactions are taken into account, however, the outcome can be strikingly different, and cooperation may spread. The underlying mechanism depends on the character of the punishment strategy. In the case of cooperating punishers,increasing the fine results in a rising cooperation level. In contrast, in the presence of the PD strategy, the phase diagram exhibits a reentrant transition as the fine is increased. Accordingly, the level of cooperation shows a non-monotonous dependence on the fine. Remarkably, punishing strategies can spread in both cases, but based on largely different mechanisms, which depend on the cooperativeness (or not) of punishers.
Ključne besede: evolutionary game theory, public goods, spatial games, punishment, social systems, moral
Objavljeno: 03.07.2017; Ogledov: 30; Prenosov: 0
.pdf Polno besedilo (823,76 KB)

Probabilistic sharing solves the problem of costly punishment
Xiaojie Chen, Attila Szolnoki, Matjaž Perc, 2014, izvirni znanstveni članek

Opis: Cooperators that refuse to participate in sanctioning defectors create the secondorder free-rider problem. Such cooperators will not be punished because they contribute to the public good, but they also eschew the costs associated with punishing defectors. Altruistic punishers - those that cooperate and punish - are at a disadvantage, and it is puzzling how such behaviour has evolved. We show that sharing the responsibility to sanction defectors rather than relying on certain individuals to do so permanently can solve the problem of costly punishment. Inspired by the fact that humans have strong but also emotional tendencies for fair play, we consider probabilistic sanctioning as the simplest way of distributing the duty. In well-mixed populations the public goods game is transformed into a coordination game with full cooperation and defection as the two stable equilibria, while in structured populations pattern formation supports additional counterintuitive solutions that are reminiscent of Parrondoʼs paradox.
Ključne besede: social dynamics, networks, punishment, public goods, econophysics
Objavljeno: 03.07.2017; Ogledov: 33; Prenosov: 0
.pdf Polno besedilo (1,52 MB)

Pacemaker-driven stochastic resonance on diffusive and complex networks of bistable oscillators
Marko Gosak, Matjaž Perc, 2008, izvirni znanstveni članek

Opis: We study the phenomenon of stochastic resonance on diffusive, small-world and scale-free networks consisting of bistable overdamped oscillators. Important thereby is the fact that the external subthreshold periodic forcing is introduced only to a single oscillator of the network. Hence, the forcing acts as a pacemaker trying to impose its rhythm on the whole network through the unit to which it is introduced. Without the addition of additive spatiotemporal noise, however, the whole network, including the unit that is directly exposed to the pacemaker, remains trapped forever in one of the two stable steady states of the local dynamics. We show that the correlation between the frequency of subthreshold pacemaker activity and the response of the network is resonantly dependent on the intensity of additive noise. The reported pacemaker-driven stochastic resonance depends most significantly on the coupling strength and the underlying network structure. Namely, the outreach of the pacemaker obeys the classic diffusion law in the case of nearest-neighbor interactions, thus being proportional to the square root of the coupling strength, whereas it becomes superdiffusive by an appropriate small-world or scale-free topology of the interaction network. In particular, the scale-free topology is identified as being optimal for the dissemination of localized rhythmic activity across the whole network. Also, we show that the ratio between the clustering coefficient and the characteristic path length is the crucial quantity defining the ability of a small-world network to facilitate the outreach of the pacemaker-emitted subthreshold rhythm. We additionally confirm these findings by using the FitzHugh-Nagumo excitable system as an alternative to the bistable overdamped oscillator.
Ključne besede: noise, bistable dynamics, stochastic simulations, complex networks
Objavljeno: 03.07.2017; Ogledov: 31; Prenosov: 0
.pdf Polno besedilo (2,18 MB)

Information sharing promotes prosocial behaviour
Attila Szolnoki, Matjaž Perc, 2013, izvirni znanstveni članek

Opis: More often than not, bad decisions are bad regardless of where and when they are made. Information sharing might thus be utilized to mitigate them. Here we show that sharing information about strategy choice between players residing on two different networks reinforces the evolution of cooperation. In evolutionary games, the strategy reflects the action of each individual that warrants the highest utility in a competitive setting. We therefore assume that identical strategies on the two networks reinforce themselves by lessening their propensity to change. Besides network reciprocity working in favour of cooperation on each individual network, we observe the spontaneous emergence of correlated behaviour between the two networks, which further deters defection. If information is shared not just between individuals but also between groups, the positive effect is even stronger, and this despite the fact that information sharing is implemented without any assumptions with regard to content.
Ključne besede: cooperation, information, social dilemma, public goods, interdependent networks, statistical physics of social systems
Objavljeno: 03.07.2017; Ogledov: 29; Prenosov: 0
.pdf Polno besedilo (756,59 KB)

Fast random rewiring and strong connectivity impair subthreshold signal detection in excitable networks
Vladislav Volman, Matjaž Perc, 2010, izvirni znanstveni članek

Opis: We study dynamical responses in locally paced networks consisting of diffusively coupled excitable units with dynamically adjusted connectivity. It is shown that for weak subthreshold pacing, excessive or strong connectivity impairs the reliable response of a network to the stimulus. Fast random dynamic rewiring of the network also acts detrimentally on signal detection by enforcing a faster relaxation upon the paced unit. Our results indicate that efficient signal processing on excitable complex networks requires tight correspondence between the dynamics of connectivity and the dynamical processes taking place on the network. This, in turn, suggests the existence of 'function-follows-form' principles for systems described within this framework.
Ključne besede: neuronal dynamics, complex networks, coevolution, cognition
Objavljeno: 03.07.2017; Ogledov: 34; Prenosov: 0
.pdf Polno besedilo (1,36 MB)

Evolutionary advantages of adaptive rewarding
Attila 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: 30.06.2017; Ogledov: 108; Prenosov: 0
.pdf Polno besedilo (2,15 MB)

Evolution of cooperation on scale-free networks subject to error and attack
Matjaž Perc, 2009, izvirni znanstveni članek

Opis: We study the evolution of cooperation in the prisoner's dilemma and the snowdrift game on scale-free networks that are subjected to intentional and random removal of vertices. We show that, irrespective of the game type, cooperation on scale-free networks is extremely robust against random deletionof vertices, but declines quickly if vertices with the maximal degree are targeted. In particular, attack tolerance is lowest if the temptation to defect is largest, whereby a small fraction of removed vertices suffices to decimate cooperators. The decline of cooperation can be directly linked to the decrease of heterogeneity of scale-free networks that sets in due to the removal of high degree vertices. We conclude that the evolution of cooperation is characterized by similar attack and error tolerance as was previously reported for information readiness and spread of viruses on scale-free networks.
Ključne besede: evolutionary game theory, social dilemma, spatial games, complex networks
Objavljeno: 30.06.2017; Ogledov: 118; Prenosov: 0
.pdf Polno besedilo (684,60 KB)

Emergence of target waves in paced populations of cyclically competing species
Luo-Luo Jiang, Tao Zhou, Matjaž Perc, Xin Huang, Bing-Hong Wang, 2009, izvirni znanstveni članek

Opis: We investigate the emergence of target waves in a cyclic predator-prey model incorporating a periodic current of the three competing species in a small area situated at the center of a square lattice. The periodic current acts as a pacemaker, trying to impose its rhythm on the overall spatiotemporal evolution of the three species. We show that the pacemaker is able to nucleate target waves that eventually spread across the whole population, whereby three routes leading to this phenomenon can be distinguished depending on the mobility of the three species and the oscillation period of the localized current. First, target waves can emerge due to the synchronization between the periodic current and oscillations of the density of the three species on the spatial grid. The second route is similar to the first, the difference being that the synchronization sets in only intermittently. Finally, the third route toward target waves is realized when the frequency of the pacemaker is much higher than that characterizing the oscillations of the overall density of the three species. By considering the mobility and frequency of the current as variable parameters, we thus provide insights into the mechanisms of pattern formation resulting from the interplay between local and global dynamics in systems governed by cyclically competing species.
Ključne besede: cyclical interactions, target waves, spatial games, diversity
Objavljeno: 30.06.2017; Ogledov: 122; Prenosov: 1
.pdf Polno besedilo (2,81 MB)

Emergence of multilevel selection in the prisoner's dilemma game on coevolving random networks
Attila Szolnoki, Matjaž Perc, 2009, izvirni znanstveni članek

Opis: We study the evolution of cooperation in the prisoner's dilemma game, whereby a coevolutionary rule is introduced that molds the random topology of the interaction network in two ways. First, existing links are deleted whenever a player adopts a new strategy or its degree exceeds a threshold value; second, new links are added randomly after a given number of game iterations. These coevolutionary processes correspond to the generic formation of new links and deletion of existing links that, especially in human societies, appear frequently as a consequence of ongoing socialization, change of lifestyle or death. Due to the counteraction of deletions and additions of links the initial heterogeneity of the interaction network is qualitatively preserved, and thus cannot be held responsible for the observed promotion of cooperation. Indeed, the coevolutionary rule evokes the spontaneous emergence of a powerful multilevel selection mechanism, which despite the sustained random topology of the evolving network, maintains cooperation across the whole span of defection temptation values.
Ključne besede: evolutionary game theory, prisoner's dilemma, spatial games, coevolution, social systems
Objavljeno: 30.06.2017; Ogledov: 143; Prenosov: 0
.pdf Polno besedilo (627,32 KB)

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