102 research outputs found
Evolutionary prisoner's dilemma game on hierarchical lattices
An evolutionary prisoner's dilemma (PD) game is studied with players located
on a hierarchical structure of layered square lattices. The players can follow
two strategies [D (defector) and C (cooperator)] and their income comes from PD
games with the ``neighbors.'' The adoption of one of the neighboring strategies
is allowed with a probability dependent on the payoff difference. Monte Carlo
simulations are performed to study how the measure of cooperation is affected
by the number of hierarchical levels (Q) and by the temptation to defect.
According to the simulations the highest frequency of cooperation can be
observed at the top level if the number of hierarchical levels is low (Q<4).
For larger Q, however, the highest frequency of cooperators occurs in the
middle layers. The four-level hierarchical structure provides the highest
average (total) income for the whole community.Comment: appendix adde
Evolutionary Prisoner's Dilemma game on the Newman-Watts networks
Maintenance of cooperation was studied for a two-strategy evolutionary
Prisoner's Dilemma game where the players are located on a one-dimensional
chain and their payoff comes from games with the nearest and next-nearest
neighbor interactions. The applied host geometry makes possible to study the
impacts of two conflicting topological features. The evolutionary rule involves
some noise affecting the strategy adoptions between the interacting players.
Using Monte Carlo simulations and the extended versions of dynamical mean-field
theory we determined the phase diagram as a function of noise level and a
payoff parameter. The peculiar feature of the diagram is changed significantly
when the connectivity structure is extended by extra links as suggested by
Newman and Watts.Comment: 4 figure
Phase diagrams for Prisoner's Dilemma game on two-dimensional lattices
The effects of payoffs and noise on the maintenance of cooperative behavior
are studied in an evolutionary Prisoner's Dilemma game with players located on
the sites of different two-dimensional lattices. This system exhibits a phase
transition from a mixed state of cooperators and defectors to a homogeneous one
where only the defectors remain alive. Using systematic Monte Carlo simulations
and different levels of the generalized mean-field approximations we have
determined the phase boundaries (critical points) separating the two phases on
the plane of the temperature (noise) and temptation to choose defection. In the
zero temperature limit this analysis suggests that the cooperation can be
sustained only for those connectivity structures where three-site clique
percolation occurs.Comment: 4 pages, 5 figure
Learning and innovative elements of strategy adoption rules expand cooperative network topologies
Cooperation plays a key role in the evolution of complex systems. However,
the level of cooperation extensively varies with the topology of agent networks
in the widely used models of repeated games. Here we show that cooperation
remains rather stable by applying the reinforcement learning strategy adoption
rule, Q-learning on a variety of random, regular, small-word, scale-free and
modular network models in repeated, multi-agent Prisoners Dilemma and Hawk-Dove
games. Furthermore, we found that using the above model systems other long-term
learning strategy adoption rules also promote cooperation, while introducing a
low level of noise (as a model of innovation) to the strategy adoption rules
makes the level of cooperation less dependent on the actual network topology.
Our results demonstrate that long-term learning and random elements in the
strategy adoption rules, when acting together, extend the range of network
topologies enabling the development of cooperation at a wider range of costs
and temptations. These results suggest that a balanced duo of learning and
innovation may help to preserve cooperation during the re-organization of
real-world networks, and may play a prominent role in the evolution of
self-organizing, complex systems.Comment: 14 pages, 3 Figures + a Supplementary Material with 25 pages, 3
Tables, 12 Figures and 116 reference
If cooperation is likely punish mildly: Insights from economic experiments based on the snowdrift game
Punishment may deter antisocial behavior. Yet to punish is costly, and the
costs often do not offset the gains that are due to elevated levels of
cooperation. However, the effectiveness of punishment depends not only on how
costly it is, but also on the circumstances defining the social dilemma. Using
the snowdrift game as the basis, we have conducted a series of economic
experiments to determine whether severe punishment is more effective than mild
punishment. We have observed that severe punishment is not necessarily more
effective, even if the cost of punishment is identical in both cases. The
benefits of severe punishment become evident only under extremely adverse
conditions, when to cooperate is highly improbable in the absence of sanctions.
If cooperation is likely, mild punishment is not less effective and leads to
higher average payoffs, and is thus the much preferred alternative. Presented
results suggest that the positive effects of punishment stem not only from
imposed fines, but may also have a psychological background. Small fines can do
wonders in motivating us to chose cooperation over defection, but without the
paralyzing effect that may be brought about by large fines. The later should be
utilized only when absolutely necessary.Comment: 15 pages, 6 figures; accepted for publication in PLoS ON
Structural power and the evolution of collective fairness in social networks
From work contracts and group buying platforms to political coalitions and international climate and economical summits, often individuals assemble in groups that must collectively reach decisions that may favor each part unequally. Here we quantify to which extent our network ties promote the evolution of collective fairness in group interactions, modeled by means of Multiplayer Ultimatum Games (MUG). We show that a single topological feature of social networks-which we call structural power-has a profound impact on the tendency of individuals to take decisions that favor each part equally. Increased fair outcomes are attained whenever structural power is high, such that the networks that tie individuals allow them to meet the same partners in different groups, thus providing the opportunity to strongly influence each other. On the other hand, the absence of such close peer-influence relationships dismisses any positive effect created by the network. Interestingly, we show that increasing the structural power of a network leads to the appearance of well-defined modules-as found in human social networks that often exhibit community structure-providing an interaction environment that maximizes collective fairness.This research was supported by Fundacao para a Ciencia e Tecnologia (FCT) through grants SFRH/BD/94736/2013, PTDC/EEI-SII/5081/2014, PTDC/MAT/STA/3358/2014 and by multi-annual funding of CBMA and INESC-ID (under the projects UID/BIA/04050/2013 and UID/CEC/50021/2013) provided by FCT. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.info:eu-repo/semantics/publishedVersio
Incipient Cognition Solves the Spatial Reciprocity Conundrum of Cooperation
Background: From the simplest living organisms to human societies, cooperation among individuals emerges as a paradox difficult to explain and describe mathematically, although very often observed in reality. Evolutionary game theory offers an excellent toolbar to investigate this issue. Spatial structure has been one of the first mechanisms promoting cooperation; however, alone it only opens a narrow window of viability. Methodology/Principal Findings: Here we equip individuals with incipient cognitive abilities, and investigate the evolution of cooperation in a spatial world where retaliation, forgiveness, treason and mutualism may coexist, as individuals engage in Prisoner’s Dilemma games. In the model, individuals are able to distinguish their partners and act towards them based on previous interactions. We show how the simplest level of cognition, alone, can lead to the emergence of cooperation. Conclusions/Significance: Despite the incipient nature of the individuals ’ cognitive abilities, cooperation emerges for unprecedented values of the temptation to cheat, being also robust to invasion by cheaters, errors in decision making an
Experimental and Kinetic Modeling Studies on the Conversion of Sucrose to Levulinic Acid and 5-Hydroxymethylfurfural Using Sulfuric Acid in Water
We
here report experimental and kinetic modeling studies on the
conversion of sucrose to levulinic acid (LA) and 5-hydroxymethylfurfural
(HMF) in water using sulfuric acid as the catalyst. Both compounds
are versatile building blocks for the synthesis of various biobased
(bulk) chemicals. A total of 24 experiments were performed in a temperature
window of 80–180 °C, a sulfuric acid concentration between
0.005 and 0.5 M, and an initial sucrose concentration between 0.05
and 0.5 M. Glucose, fructose, and HMF were detected as the intermediate
products. The maximum LA yield was 61 mol %, obtained at 160 °C,
an initial sucrose concentration of 0.05 M, and an acid concentration
of 0.2 M. The maximum HMF yield (22 mol %) was found for an acid concentration
of 0.05 M, an initial sucrose concentration of 0.05 M, and a temperature
of 140 °C. The experimental data were modeled using a number
of possible reaction networks. The best model was obtained when using
a first order approach in substrates (except for the reversion of
glucose) and agreement between experiment and model was satisfactorily.
The implication of the model regarding batch optimization is also
discussed
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