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1.
Local and global stimuli in reinforcement learning
Danyang Jia, Hao Guo, Zhao Song, Lei Shi, Xinyang Deng, Matjaž Perc, Zhen Wang, 2021, izvirni znanstveni članek

Opis: In efforts to resolve social dilemmas, reinforcement learning is an alternative to imitation and exploration in evolutionary game theory. While imitation and exploration rely on the performance of neighbors, in reinforcement learning individuals alter their strategies based on their own performance in the past. For example, according to the Bush-Mosteller model of reinforcement learning, an individual's strategy choice is driven by whether the received payoff satisfies a preset aspiration or not. Stimuli also play a key role in reinforcement learning in that they can determine whether a strategy should be kept or not. Here we use the Monte Carlo method to study pattern formation and phase transitions towards cooperation in social dilemmas that are driven by reinforcement learning. We distinguish local and global players according to the source of the stimulus they experience. While global players receive their stimuli from the whole neighborhood, local players focus solely on individual performance. We show that global players play a decisive role in ensuring cooperation, while local players fail in this regard, although both types of players show properties of "moody cooperators". In particular, global players evoke stronger conditional cooperation in their neighborhoods based on direct reciprocity, which is rooted in the emerging spatial patterns and stronger interfaces around cooperative clusters.
Ključne besede: evolutionary game theory, cooperation, learning, social physics
Objavljeno v DKUM: 03.03.2025; Ogledov: 0; Prenosov: 1
.pdf Celotno besedilo (5,68 MB)
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2.
Communicating sentiment and outlook reverses inaction against collective risks
Zhen Wang, Marko Jusup, Hao Guo, Lei Shi, Sunčana Geček, Madhur Anand, Matjaž Perc, Chris T. Bauch, Jürgen Kurths, Stefano Boccaletti, Hans-Joachim Schellnhuber, 2020, izvirni znanstveni članek

Opis: Collective risks permeate society, triggering social dilemmas in which working toward a common goal is impeded by selfish interests. One such dilemma is mitigating runaway climate change. To study the social aspects of climate-change mitigation, we organized an experimental game and asked volunteer groups of three different sizes to invest toward a common mitigation goal. If investments reached a preset target, volunteers would avoid all consequences and convert their remaining capital into monetary payouts. In the opposite case, however, volunteers would lose all their capital with 50% probability. The dilemma was, therefore, whether to invest one's own capital or wait for others to step in. We find that communicating sentiment and outlook helps to resolve the dilemma by a fundamental shift in investment patterns. Groups in which communication is allowed invest persistently and hardly ever give up, even when their current investment deficits are substantial. The improved investment patterns are robust to group size, although larger groups are harder to coordinate, as evidenced by their overall lower success frequencies. A clustering algorithm reveals three behavioral types and shows that communication reduces the abundance of the free-riding type. Climate-change mitigation, however, is achieved mainly by cooperator and altruist types stepping up and increasing contributions as the failure looms. Meanwhile, contributions from free riders remain flat throughout the game. This reveals that the mechanisms behind avoiding collective risks depend on an interaction between behavioral type, communication, and timing.
Ključne besede: social dilemma, free riding, climate change, negotiation, group size, COVID-19
Objavljeno v DKUM: 07.01.2025; Ogledov: 0; Prenosov: 4
.pdf Celotno besedilo (1,07 MB)
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3.
Diverse strategic identities induce dynamical states in evolutionary games
Irene Sendiña-Nadal, Inmaculada Leyva, Matjaž Perc, David Papo, Marko Jusup, Zhen Wang, Juan A. Almendral, Pouya Manshour, Stefano Boccaletti, 2020, izvirni znanstveni članek

Opis: Evolutionary games provide the theoretical backbone for many aspects of our social life: from cooperation to crime, from climate inaction to imperfect vaccination and epidemic spreading, from antibiotics overuse to biodiversity preservation. An important, and so far overlooked, aspect of reality is the diverse strategic identities of individuals. While applying the same strategy to all interaction partners may be an acceptable assumption for simpler forms of life, this fails to account for the behavior of more complex living beings. For instance, we humans act differently around different people. Here we show that allowing individuals to adopt different strategies with different partners yields a very rich evolutionary dynamics, including time-dependent coexistence of cooperation and defection, systemwide shifts in the dominant strategy, and maturation in individual choices. Our results are robust to variations in network type and size, and strategy updating rules. Accounting for diverse strategic identities thus has far-reaching implications in the mathematical modeling of social games.
Ključne besede: cooperation, evolutionary game theory, social physics, collective dynamics, complex system
Objavljeno v DKUM: 20.11.2024; Ogledov: 0; Prenosov: 4
.pdf Celotno besedilo (4,71 MB)
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4.
Evolutionary games on multilayer networks : a colloquium
Zhen Wang, Lin Wang, Attila Szolnoki, Matjaž Perc, 2015, pregledni znanstveni članek

Opis: Networks form the backbone of many complex systems, ranging from the Internet to human societies. Accordingly, not only is the range of our interactions limited and thus best described and modeled by networks, it is also a fact that the networks that are an integral part of such models are often interdependent or even interconnected. Networks of networks or multilayer networks are therefore a more apt description of social systems. This colloquium is devoted to evolutionary games on multilayer networks, and in particular to the evolution of cooperation as one of the main pillars of modern human societies. We first give an overview of the most significant conceptual differences between single-layer and multilayer networks, and we provide basic definitions and a classification of the most commonly used terms. Subsequently, we review fascinating and counterintuitive evolutionary outcomes that emerge due to different types of interdependencies between otherwise independent populations. The focus is on coupling through the utilities of players, through the flow of information, as well as through the popularity of different strategies on different network layers. The colloquium highlights the importance of pattern formation and collective behavior for the promotion of cooperation under adverse conditions, as well as the synergies between network science and evolutionary game theory.
Ključne besede: kooperacija, sociološke mreže, evolucijske igre, kolektivni pojav, samo-organizacija, fazni prehodi, recipročnost, fizika socioloških sistemov, cooperation, social networks, evolutionary games, collective phenomena, self-organization, phase transitions, reciprocity, physics of social systems
Objavljeno v DKUM: 17.09.2024; Ogledov: 0; Prenosov: 2
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5.
Reputation and reciprocity : review
Chengyi Xia, Juan Wang, Matjaž Perc, Zhen Wang, 2023, pregledni znanstveni članek

Opis: Reputation and reciprocity are key mechanisms for cooperation in human societies, often going hand in hand to favor prosocial behavior over selfish actions. Here we review recent researches at the interface of physics and evolutionary game theory that explored these two mechanisms. We focus on image scoring as the bearer of reputation, as well as on various types of reciprocity, including direct, indirect, and network reciprocity. We review different definitions of reputation and reciprocity dynamics, and we show how these affect the evolution of cooperation in social dilemmas. We consider first-order, second-order, as well as higherorder models in well-mixed and structured populations, and we review experimental works that support and inform the results of mathematical modeling and simulations. We also provide a synthesis of the reviewed researches along with an outlook in terms of six directions that seem particularly promising to explore in the future.
Ključne besede: pattern formation, Monte Carlo method, complex network, evolutionary game theory, cooperation, social physics
Objavljeno v DKUM: 20.06.2024; Ogledov: 154; Prenosov: 39
.pdf Celotno besedilo (4,71 MB)
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6.
Self-organization towards optimally interdependent networks by means of coevolution
Zhen 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: 1329; Prenosov: 424
.pdf Celotno besedilo (887,51 KB)
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7.
Wisdom of groups promotes cooperation in evolutionary social dilemmas
Attila 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: 1366; Prenosov: 406
.pdf Celotno besedilo (646,99 KB)
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8.
Optimal interdependence between networks for the evolution of cooperation
Zhen Wang, Attila Szolnoki, Matjaž Perc, 2013, izvirni znanstveni članek

Opis: Recent research has identified interactions between networks as crucial for the outcome of evolutionary games taking place on them. While the consensus is that interdependence does promote cooperation by means of organizational complexity and enhanced reciprocity that is out of reach on isolated networks, we here address the question just how much interdependence there should be. Intuitively, one might assume the more the better. However, we show that in fact only an intermediate density of sufficiently strong interactions between networks warrants an optimal resolution of social dilemmas. This is due to an intricate interplay between the heterogeneity that causes an asymmetric strategy flow because of the additional links between the networks, and the independent formation of cooperative patterns on each individual network. Presented results are robust to variations of the strategy updating rule, the topology of interdependent networks, and the governing social dilemma, thus suggesting a high degree of universality.
Ključne besede: social dilemma, cooperation, public goods, biased utility, interdependent networks, statistical physics of social systems
Objavljeno v DKUM: 23.06.2017; Ogledov: 1213; Prenosov: 385
.pdf Celotno besedilo (658,72 KB)
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9.
Interdependent network reciprocity in evolutionary games
Zhen Wang, Attila Szolnoki, Matjaž Perc, 2013, izvirni znanstveni članek

Opis: Besides the structure of interactions within networks, also the interactions between networks are of the outmost importance. We therefore study the outcome of the public goods game on two interdependent networks that are connected by means of a utility function, which determines how payoffs on both networks jointly influence the success of players in each individual network. We show that an unbiased coupling allows the spontaneous emergence of interdependent network reciprocity, which is capable to maintain healthy levels of public cooperation even in extremely adverse conditions. The mechanism, however, requires simultaneous formation of correlated cooperator clusters on both networks. If this does not emerge or if the coordination process is disturbed, network reciprocity fails, resulting in the total collapse of cooperation. Network interdependence can thus be exploited effectively to promote cooperation past the limits imposed by isolated networks, but only if the coordination between the interdependent networks is not disturbed.
Ključne besede: social dilemma, cooperation, public goods, biased utility, interdependent networks, statistical physics of social systems
Objavljeno v DKUM: 23.06.2017; Ogledov: 1288; Prenosov: 397
.pdf Celotno besedilo (741,04 KB)
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10.
If players are sparse social dilemmas are too: importance of percolation for evolution of cooperation
Zhen 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: 1273; Prenosov: 375
.pdf Celotno besedilo (413,53 KB)
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