1. Local and global stimuli in reinforcement learningDanyang 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
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2. The self-organizing impact of averaged payoffs on the evolution of cooperationAttila Szolnoki, Matjaž Perc, 2021, izvirni znanstveni članek Opis: According to the fundamental principle of evolutionary game theory, the more successful strategy in a population should spread. Hence, during a strategy imitation process a player compares its payoff value to the payoff value held by a competing strategy. But this information is not always accurate. To avoid ambiguity a learner may therefore decide to collect a more reliable statistics by averaging the payoff values of its opponents in the neighborhood, and makes a decision afterwards. This simple alteration of the standard microscopic protocol significantly improves the cooperation level in a population. Furthermore, the positive impact can be strengthened by increasing the role of the environment and the size of the evaluation circle. The mechanism that explains this improvement is based on a self-organizing process which reveals the detrimental consequence of defector aggregation that remains partly hidden during face-to-face comparisons. Notably, the reported phenomenon is not limited to lattice populations but remains valid also for systems described by irregular interaction networks. Ključne besede: evolutionary game theory, cooperation, learning, social physics Objavljeno v DKUM: 03.03.2025; Ogledov: 0; Prenosov: 2
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3. Optimal governance and implementation of vaccination programmes to contain the COVID-19 pandemicMahendra Piraveenan, Shailendra Sawleshwarkar, Michael Walsh, Iryna Zablotska, Samit Bhattacharyya, Habib Hassan Farooqui, Tarun Bhatnagar, Anup Karan, Manoj Murhekar, Sanjay P. Zodpey, K. S. Mallikarjuna Rao, Philippa Pattison, Albert Y. Zomaya, Matjaž Perc, 2021, izvirni znanstveni članek Opis: Since the recent introduction of several viable vaccines for SARS-CoV-2, vaccination uptake has become the key factor that will determine our success in containing the COVID-19 pandemic. We argue that game theory and social network models should be used to guide decisions pertaining to vaccination programmes for the best possible results. In the months following the introduction of vaccines, their availability and the human resources needed to run the vaccination programmes have been scarce in many countries. Vaccine hesitancy is also being encountered from some sections of the general public. We emphasize that decision-making under uncertainty and imperfect information, and with only conditionally optimal outcomes, is a unique forte of established game-theoretic modelling. Therefore, we can use this approach to obtain the best framework for modelling and simulating vaccination prioritization and uptake that will be readily available to inform important policy decisions for the optimal control of the COVID-19 pandemic. Ključne besede: COVID-19, evolutionary game theory, digital epidemiology, vaccination, social network, public goods game, social physics Objavljeno v DKUM: 28.02.2025; Ogledov: 0; Prenosov: 3
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4. Dissimilarity-driven behavior and cooperation in the spatial public goods gameYinhai Fang, Tina Perc Benko, Matjaž Perc, Haiyan Xu, 2019, izvirni znanstveni članek Opis: In this paper, we explore the impact of four different types of dissimilarity-driven behavior on the evolution of cooperation in the spatial public goods game. While it is commonly assumed that individuals adapt their strategy by imitating one of their more successful neighbors, in reality only very few will be awarded the highest payoffs. Many have equity or equality preferences, and they have to make do with an average or even with a low payoff. To account for this, we divide the population into two categories. One consists of payoff-driven players, while the other consists of dissimilarity-driven players. The later imitate the minority strategy in their group based on four different dissimilaritydriven behaviors. The rule that most effectively promotes cooperation, and this regardless of the multiplication factor of the public goods game, is when individuals adopt the minority strategy only when their payoff is better than that of their neighbors. If the dissimilarity-driven players adopt the minority strategy regardless of the payoffs of others, or if their payoff is the same, the population typically evolves towards a neutral state where cooperators and defectors are equally common. This may be beneficial when the multiplication factor is low, when defectors would otherwise dominate. However, if the dissimilarity-driven players adopt the minority strategy only when their payoff is worse than that of their neighbors, then cooperation is not promoted at all in comparison to the baseline case in the absence of dissimilarity-driven behavior. We explore the pattern formation behind these results, and we discuss their wider implications for the better understanding of cooperative behavior in social groups. Ključne besede: theoretical biology, evolution, agent-based modeling, complex system, network science, evolutionary game theory Objavljeno v DKUM: 26.02.2025; Ogledov: 0; Prenosov: 3
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5. Identification of influential invaders in evolutionary populationsGuoli Yang, Tina Perc Benko, Matteo Cavaliere, Jincai Huang, Matjaž Perc, 2019, izvirni znanstveni članek Opis: The identification of the most influential nodes has been a vibrant subject of research across the whole of network science. Here we map this problem to structured evolutionary populations, where strategies and the interaction network are both subject to change over time based on social inheritance. We study cooperative communities, which cheaters can invade because they avoid the cost of contributions that are associated with cooperation. The question that we seek to answer is at which nodes cheaters invade most successfully. We propose the weighted degree decomposition to identify and rank the most influential invaders. More specifically, we distinguish two kinds of ranking based on the weighted degree decomposition. We show that a ranking strategy based on negative-weighted degree allows to successfully identify the most influential invaders in the case of weak selection, while a ranking strategy based on positive-weighted degree performs better when the selection is strong. Our research thus reveals how to identify the most influential invaders based on statistical measures in dynamically evolving cooperative communities. Ključne besede: theoretical biology, evolution, agent-based modeling, complex system, network science, evolutionary game theory Objavljeno v DKUM: 26.02.2025; Ogledov: 0; Prenosov: 4
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6. Evolutionary dynamics of any multiplayer game on regular graphsChaoqian Wang, Matjaž Perc, Attila Szolnoki, 2024, izvirni znanstveni članek Opis: Multiplayer games on graphs are at the heart of theoretical descriptions of key evolutionary processes that govern vital social and natural systems. However, a comprehensive theoretical framework for solving multiplayer games with an arbitrary number of strategies on graphs is still missing. Here, we solve this by drawing an analogy with the Balls-and-Boxes problem, based on which we show that the local configuration of multiplayer games on graphs is equivalent to distributing k identical co-players among n distinct strategies. We use this to derive the replicator equation for any n-strategy multiplayer game under weak selection, which can be solved in polynomial time. As an example, we revisit the second-order free-riding problem, where costly punishment cannot truly resolve social dilemmas in a well-mixed population. Yet, in structured populations, we derive an accurate threshold for the punishment strength, beyond which punishment can either lead to the extinction of defection or transform
the system into a rock-paper-scissors-like cycle. The analytical solution also qualitatively agrees with the phase diagrams that were previously obtained for non-marginal selection strengths. Our framework thus allows an exploration of any multi-strategy multiplayer game on regular graphs. Ključne besede: evolutionary game theory, cooperation, network, social physics Objavljeno v DKUM: 26.02.2025; Ogledov: 0; Prenosov: 3
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7. Cooperation on interdependent networks by means of migration and stochastic imitationSayantan Nag Chowdhury, Srilena Kundu, Maja Duh, Matjaž Perc, Dibakar Ghosh, 2020, izvirni znanstveni članek Opis: Evolutionary game theory in the realm of network science appeals to a lot of research communities, as it constitutes a popular theoretical framework for studying the evolution of cooperation in social dilemmas. Recent research has shown that cooperation is markedly more resistant in interdependent networks, where traditional network reciprocity can be further enhanced due to various forms of interdependence between different network layers. However, the role of mobility in interdependent networks is yet to gain its well-deserved attention. Here we consider an interdependent network model, where individuals in each layer follow different evolutionary games, and where each player is considered as a mobile agent that can move locally inside its own layer to improve its fitness. Probabilistically, we also consider an imitation possibility from a neighbor on the other layer. We show that, by considering migration and stochastic imitation, further fascinating gateways to cooperation on interdependent networks can be observed. Notably, cooperation can be promoted on both layers, even if cooperation without interdependence would be improbable on one of the layers due to adverse conditions. Our results provide a rationale for engineering better social systems at the interface of networks and human decision making under testing dilemmas. Ključne besede: cooperation, interdependent networks, mobile agents, prisoner's dilemma, snowdrift game, game theory, mobility, rational agents Objavljeno v DKUM: 15.01.2025; Ogledov: 0; Prenosov: 5
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8. Language-based game theory in the age of artificial intelligenceValerio Capraro, Roberto Di Paolo, Matjaž Perc, Veronica Pizziol, 2024, pregledni znanstveni članek Opis: Understanding human behaviour in decision problems and strategicinteractions has wide-ranging applications in economics, psychology andartificial intelligence. Game theory offers a robust foundation for this under-standing, based on the idea that individuals aim to maximize a utilityfunction. However, the exact factors influencing strategy choices remainelusive. While traditional models try to explain human behaviour as a func-tion of the outcomes of available actions, recent experimental researchreveals that linguistic content significantly impacts decision-making, thusprompting a paradigm shift from outcome-based to language-based utilityfunctions. This shift is more urgent than ever, given the advancement ofgenerative AI, which has the potential to support humans in making criticaldecisions through language-based interactions. We propose sentiment analy-sis as a fundamental tool for this shift and take an initial step by analysing61 experimental instructions from the dictator game, an economic gamecapturing the balance between self-interest and the interest of others,which is at the core of many social interactions. Our meta-analysis showsthat sentiment analysis can explain human behaviour beyond economicoutcomes. We discuss future research directions. We hope this worksets the stage for a novel game-theoretical approach that emphasizes theimportance of language in human decisions. Ključne besede: game theory, artificial intelligence, social preferences, language-based preferences, social physics, moral behavior, trust Objavljeno v DKUM: 27.11.2024; Ogledov: 0; Prenosov: 363
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9. Diverse strategic identities induce dynamical states in evolutionary gamesIrene 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
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10. Strategically positioning cooperators can facilitate the contagion of cooperationGuoli Yang, Matteo Cavaliere, Cheng Zhu, Matjaž Perc, 2021, izvirni znanstveni članek Opis: The spreading of cooperation in structured population is a challenging problem which can be observed at diferent scales of social and biological organization. Generally, the problem is studied by evaluating the chances that few initial invading cooperators, randomly appearing in a network, can lead to the spreading of cooperation. In this paper we demonstrate that in many scenarios some cooperators are more infuential than others and their initial positions can facilitate the spreading of cooperation. We investigate six diferent ways to add initial cooperators in a network of cheaters, based on diferent network-based measurements. Our research reveals that strategically positioning the initial cooperators in a population of cheaters allows to decrease the number of initial cooperators necessary to successfully seed cooperation. The strategic positioning of initial cooperators can also help to shorten the time necessary for the restoration of cooperation. The optimal ways in which the initial cooperators should be placed is, however, non-trivial in that it depends on the degree of competition, the underlying game, and the network structure. Overall, our results show that, in structured populations, few cooperators, well positioned in strategically chosen places, can spread cooperation faster and easier than a large number of cooperators that are placed badly. Ključne besede: cooperation, evolutionary game theory, social physics, collective dynamics, complex system Objavljeno v DKUM: 22.10.2024; Ogledov: 0; Prenosov: 3
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