11,550 research outputs found
Evolution of cooperation on dynamical graphs
There are two key characteristic of animal and human societies: (1) degree heterogeneity, meaning that not all individual have the same number of associates; and (2) the interaction topology is not static, i.e. either individuals interact with different set of individuals at different times of their life, or at least they have different associations than their parents. Earlier works have shown that population structure is one of the mechanisms promoting cooperation. However, most studies had assumed that the interaction network can be described by a regular graph (homogeneous degree distribution). Recently there are an increasing number of studies employing degree heterogeneous graphs to model interaction topology. But mostly the interaction topology was assumed to be static. Here we investigate the fixation probability of the cooperator strategy in the prisoner’s dilemma, when interaction network is a random regular graph, a random graph or a scale-free graph and the interaction network is allowed to change.
We show that the fixation probability of the cooperator strategy is lower when the interaction topology is described by a dynamical graph compared to a static graph. Even a limited network dynamics significantly decreases the fixation probability of cooperation, an effect that is mitigated stronger by degree heterogeneous networks topology than by a degree homogeneous one. We have also found that from the considered graph topologies the decrease of fixation probabilities due to graph dynamics is the lowest on scale-free graphs
Conformity Hinders the Evolution of Cooperation on Scale-Free Networks
We study the effects of conformity, the tendency of humans to imitate locally
common behaviors, in the evolution of cooperation when individuals occupy the
vertices of a graph and engage in the one-shot Prisoner's Dilemma or the
Snowdrift game with their neighbors. Two different graphs are studied: rings
(one-dimensional lattices with cyclic boundary conditions) and scale-free
networks of the Barabasi-Albert type. The proposed evolutionary-graph model is
studied both by means of Monte Carlo simulations and an extended
pair-approximation technique. We find improved levels of cooperation when
evolution is carried on rings and individuals imitate according to both the
traditional pay-off bias and a conformist bias. More important, we show that
scale-free networks are no longer powerful amplifiers of cooperation when fair
amounts of conformity are introduced in the imitation rules of the players.
Such weakening of the cooperation-promoting abilities of scale-free networks is
the result of a less biased flow of information in scale-free topologies,
making hubs more susceptible of being influenced by less-connected neighbors.Comment: 14 pages, 11 figure
Mutual Trust and Cooperation in the Evolutionary Hawks-Doves Game
Using a new dynamical network model of society in which pairwise interactions
are weighted according to mutual satisfaction, we show that cooperation is the
norm in the Hawks-Doves game when individuals are allowed to break ties with
undesirable neighbors and to make new acquaintances in their extended
neighborhood. Moreover, cooperation is robust with respect to rather strong
strategy perturbations. We also discuss the empirical structure of the emerging
networks, and the reasons that allow cooperators to thrive in the population.
Given the metaphorical importance of this game for social interaction, this is
an encouraging positive result as standard theory for large mixing populations
prescribes that a certain fraction of defectors must always exist at
equilibrium.Comment: 23 pages 12 images, to appea
Different reactions to adverse neighborhoods in games of cooperation
In social dilemmas, cooperation among randomly interacting individuals is
often difficult to achieve. The situation changes if interactions take place in
a network where the network structure jointly evolves with the behavioral
strategies of the interacting individuals. In particular, cooperation can be
stabilized if individuals tend to cut interaction links when facing adverse
neighborhoods. Here we consider two different types of reaction to adverse
neighborhoods, and all possible mixtures between these reactions. When faced
with a gloomy outlook, players can either choose to cut and rewire some of
their links to other individuals, or they can migrate to another location and
establish new links in the new local neighborhood. We find that in general
local rewiring is more favorable for the evolution of cooperation than
emigration from adverse neighborhoods. Rewiring helps to maintain the diversity
in the degree distribution of players and favors the spontaneous emergence of
cooperative clusters. Both properties are known to favor the evolution of
cooperation on networks. Interestingly, a mixture of migration and rewiring is
even more favorable for the evolution of cooperation than rewiring on its own.
While most models only consider a single type of reaction to adverse
neighborhoods, the coexistence of several such reactions may actually be an
optimal setting for the evolution of cooperation.Comment: 12 pages, 5 figures; accepted for publication in PLoS ON
Selection of noise level in strategy adoption for spatial social dilemmas
We studied spatial Prisoner's Dilemma and Stag Hunt games where both the
strategy distribution and the players' individual noise level could evolve to
reach higher individual payoff. Players are located on the sites of different
two-dimensional lattices and gain their payoff from games with their neighbors
by choosing unconditional cooperation or defection. The way of strategy
adoption can be characterized by a single (temperature-like) parameter
describing how strongly adoptions depend on the payoff-difference. If we start
the system from a random strategy distribution with many different player
specific parameters, the simultaneous evolution of strategies and
parameters drives the system to a final stationary state where only one
value remains. In the coexistence phase of cooperator and defector strategies
the surviving parameter is in good agreement with the noise level that
ensures the highest cooperation level if uniform is supposed for all
players. In this paper we give a thorough overview about the properties of this
evolutionary process.Comment: 10 two-column pages, 10 figures; accepted for publication in Physical
Review
Coevolutionary games - a mini review
Prevalence of cooperation within groups of selfish individuals is puzzling in
that it contradicts with the basic premise of natural selection. Favoring
players with higher fitness, the latter is key for understanding the challenges
faced by cooperators when competing with defectors. Evolutionary game theory
provides a competent theoretical framework for addressing the subtleties of
cooperation in such situations, which are known as social dilemmas. Recent
advances point towards the fact that the evolution of strategies alone may be
insufficient to fully exploit the benefits offered by cooperative behavior.
Indeed, while spatial structure and heterogeneity, for example, have been
recognized as potent promoters of cooperation, coevolutionary rules can extend
the potentials of such entities further, and even more importantly, lead to the
understanding of their emergence. The introduction of coevolutionary rules to
evolutionary games implies, that besides the evolution of strategies, another
property may simultaneously be subject to evolution as well. Coevolutionary
rules may affect the interaction network, the reproduction capability of
players, their reputation, mobility or age. Here we review recent works on
evolutionary games incorporating coevolutionary rules, as well as give a
didactic description of potential pitfalls and misconceptions associated with
the subject. In addition, we briefly outline directions for future research
that we feel are promising, thereby particularly focusing on dynamical effects
of coevolutionary rules on the evolution of cooperation, which are still widely
open to research and thus hold promise of exciting new discoveries.Comment: 24 two-column pages, 10 figures; accepted for publication in
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