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1.
Heterogeneous aspirations promote cooperation in the prisoner's dilemma game
Matjaž Perc, Zhen Wang, 2010, izvirni znanstveni članek

Opis: 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.
Ključne besede: evolutionary game theory, prisoner's dilemma, spatial games, aspirations, social systems, physics and society
Objavljeno: 19.06.2017; Ogledov: 423; Prenosov: 157
.pdf Celotno besedilo (822,95 KB)
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2.
Flights towards defection in economic transactions
Matjaž Perc, 2007, izvirni znanstveni članek

Opis: We show that Lévy distributed variations of payoffs in the prisoner's dilemma game impede cooperation as the frequency of rare events increases. Lévy flights thus facilitate defection, but also uphold the evolutionary process, arguably maintaining a healthy level of competitiveness amongst the agents.
Ključne besede: chaotic systems, game theory, Lévy process, cooperation, social welfare
Objavljeno: 07.06.2012; Ogledov: 994; Prenosov: 43
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3.
Microeconomic uncertainties facilitate cooperative alliances and social welfare
Matjaž Perc, 2007, izvirni znanstveni članek

Opis: We show that microeconomic chaotic variations of payoffs in the prisoner's dilemma game maintain cooperation over a broad range of defection temptation values where otherwise economic stalemate reigns. Thus, unpredictability at micro scales impedes mutual defection that inflicts social poverty.
Ključne besede: chaotic systems, game theory, microeconomic chaos, cooperation, social welfare
Objavljeno: 07.06.2012; Ogledov: 995; Prenosov: 49
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Adaptive and bounded investment returns promote cooperation in spatial public goods games
Xiaojie Chen, Yongkui Liu, Yonghui Zhou, Long Wang, Matjaž Perc, 2012, izvirni znanstveni članek

Opis: The public goods game is one of the most famous models for studying the evolution of cooperation in sizable groups. The multiplication factor in this game can characterize the investment return from the public good, which may be variable depending on the interactive environment in realistic situations. Instead of using the same universal value, here we consider that the multiplication factor in each group is updated based on the differences between the local and global interactive environments in the spatial public goods game, but meanwhile limited to within a certain range. We find that the adaptive and bounded investment returns can significantly promote cooperation. In particular, full cooperation can be achieved for high feedback strength when appropriate limitation is set for the investment return. Also, we show that the fraction of cooperators in the whole population can become larger if the lower and upper limits of the multiplication factor are increased. Furthermore, in comparison to the traditionally spatial public goods game where the multiplication factor in each group is identical and fixed, we find that cooperation can be better promoted if the multiplication factor is constrained to adjust between one and the group size in our model. Our results highlight the importance of the locally adaptive and bounded investment returns for the emergence and dominance of cooperative behavior in structured populations.
Ključne besede: cooperation, public goods, social dilemmas, physics of social systems
Objavljeno: 19.06.2017; Ogledov: 256; Prenosov: 165
.pdf Celotno besedilo (590,51 KB)
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6.
Directional learning and the provisioning of public goods
Heinrich 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: 23.06.2017; Ogledov: 197; Prenosov: 140
.pdf Celotno besedilo (1,40 MB)
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7.
An evolutionary inspection game with labour unions on small-world networks
Salahuddin M. Kamal, Yas Al-Hadeethi, Fouad A. Abolaban, Fahad M. Al-Marzouki, Matjaž Perc, 2015, izvirni znanstveni članek

Opis: We study an evolutionary inspection game where agents can chose between working and shirking. The evolutionary process is staged on a small-world network, through which agents compare their incomes and, based on the outcome, decide which strategy to adopt. Moreover, we introduce union members that have certain privileges, of which the extent depends on the bargaining power of the union. We determine how the union affects the overall performance of the firm that employs the agents, and what are its influences on the employees. We find that, depending on its bargaining power, the union has significant leverage to deteriorate the productivity of a firm, and consequently also to lower the long-run benefits of the employees.
Ključne besede: cooperation, public goods, inspection, unions, physics of social systems
Objavljeno: 23.06.2017; Ogledov: 249; Prenosov: 135
.pdf Celotno besedilo (568,84 KB)
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8.
A double-edged sword: benefits and pitfalls of heterogeneous punishment in evolutionary inspection games
Matjaž Perc, Attila Szolnoki, 2015, izvirni znanstveni članek

Opis: As a simple model for criminal behavior, the traditional two-strategy inspection game yields counterintuitive results that fail to describe empirical data. The latter shows that crime is often recurrent, and that crime rates do not respond linearly to mitigation attempts. A more apt model entails ordinary people who neither commit nor sanction crime as the third strategy besides the criminals and punishers. Since ordinary people free-ride on the sanctioning efforts of punishers, they may introduce cyclic dominance that enables the coexistence of all three competing strategies. In this setup ordinary individuals become the biggest impediment to crime abatement. We therefore also consider heterogeneous punisher strategies, which seek to reduce their investment into fighting crime in order to attain a more competitive payoff. We show that this diversity of punishment leads to an explosion of complexity in the system, where the benefits and pitfalls of criminal behavior are revealed in the most unexpected ways. Due to the raise and fall of different alliances no less than six consecutive phase transitions occur in dependence on solely the temptation to succumb to criminal behavior, leading the population from ordinary people-dominated across punisher-dominated to crime-dominated phases, yet always failing to abolish crime completely.
Ključne besede: crime, phase transition, social dilemma, physics of social systems
Objavljeno: 23.06.2017; Ogledov: 212; Prenosov: 182
.pdf Celotno besedilo (1,62 MB)
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9.
Stability of cooperation under image scoring in group interactions
Heinrich H. Nax, Matjaž Perc, Attila Szolnoki, Dirk Helbing, 2015, izvirni znanstveni članek

Opis: Image scoring sustains cooperation in the repeated two-player prisoner's dilemma through indirect reciprocity, even though defection is the uniquely dominant selfish behaviour in the one-shot game. Many real-world dilemma situations, however, firstly, take place in groups and, secondly, lack the necessary transparency to inform subjects reliably of others' individual past actions. Instead, there is revelation of information regarding groups, which allows for "group scoring" but not for image scoring. Here, we study how sensitive the positive results related to image scoring are to information based on group scoring. We combine analytic results and computer simulations to specify the conditions for the emergence of cooperation. We show that under pure group scoring, that is, under the complete absence of image-scoring information, cooperation is unsustainable. Away from this extreme case, however, the necessary degree of image scoring relative to group scoring depends on the population size and is generally very small. We thus conclude that the positive results based on image scoring apply to a much broader range of informational settings that are relevant in the real world than previously assumed.
Ključne besede: public goods, group interactions, phase transition, social dilemma, physics of social systems
Objavljeno: 23.06.2017; Ogledov: 501; Prenosov: 167
.pdf Celotno besedilo (329,32 KB)
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10.
Evolution of public cooperation in a monitored society with implicated punishment and within-group enforcement
Xiaojie Chen, Tatsuya Sasaki, Matjaž Perc, 2015, izvirni znanstveni članek

Opis: Monitoring with implicated punishment is common in human societies to avert freeriding on common goods. But is it effective in promoting public cooperation? We show that the introduction of monitoring and implicated punishment is indeed effective, as it transforms the public goods game to a coordination game, thus rendering cooperation viable in infinite and finite well-mixed populations. We also show that the addition of within-group enforcement further promotes the evolution of public cooperation. However, although the group size in this context has nonlinear effects on collective action, an intermediate group size is least conductive to cooperative behaviour. This contradicts recent field observations, where an intermediate group size was declared optimal with the conjecture that group-size effects and within-group enforcement are responsible. Our theoretical research thus clarifies key aspects of monitoring with implicated punishment in human societies, and additionally, it reveals fundamental group-size effects that facilitate prosocial collective action.
Ključne besede: cooperation, public goods, punishment, sustainable development, physics of social systems
Objavljeno: 23.06.2017; Ogledov: 287; Prenosov: 163
.pdf Celotno besedilo (1,50 MB)
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