300 research outputs found
Zealots tame oscillations in the spatial rock-paper-scissors game
The rock-paper-scissors game is a paradigmatic model for biodiversity, with
applications ranging from microbial populations to human societies. Research
has shown, however, that mobility jeopardizes biodiversity by promoting the
formation of spiral waves, especially if there is no conservation law in place
for the total number of competing players. Firstly, we show that even if such a
conservation law applies, mobility still jeopardizes biodiversity in the
spatial rock-paper-scissors game if only a small fraction of links of the
square lattice is randomly rewired. Secondly, we show that zealots are very
effective in taming the amplitude of oscillations that emerge due to mobility
and/or interaction randomness, and this regardless of whether the later is
quenched or annealed. While even a tiny fraction of zealots brings significant
benefits, at 5\% occupancy zealots practically destroy all oscillations
regardless of the intensity of mobility, and regardless of the type and
strength of randomness in the interaction structure. Interestingly, by annealed
randomness the impact of zealots is qualitatively the same as by mobility,
which highlights that fast diffusion does not necessarily destroy the
coexistence of species, and that zealotry thus helps to recover the stable
mean-field solution. Our results strengthen the important role of zealots in
models of cyclic dominance, and they reveal fascinating evolutionary outcomes
in structured populations that are a unique consequence of such uncompromising
behavior.Comment: 6 two-column pages, 4 figures; accepted for publication in Physical
Review
Optimal distribution of incentives for public cooperation in heterogeneous interaction environments
In the framework of evolutionary games with institutional reciprocity,
limited incentives are at disposal for rewarding cooperators and punishing
defectors. In the simplest case, it can be assumed that, depending on their
strategies, all players receive equal incentives from the common pool. The
question arises, however, what is the optimal distribution of institutional
incentives? How should we best reward and punish individuals for cooperation to
thrive? We study this problem for the public goods game on a scale-free
network. We show that if the synergetic effects of group interactions are weak,
the level of cooperation in the population can be maximized simply by adopting
the simplest "equal distribution" scheme. If synergetic effects are strong,
however, it is best to reward high-degree nodes more than low-degree nodes.
These distribution schemes for institutional rewards are independent of payoff
normalization. For institutional punishment, however, the same optimization
problem is more complex, and its solution depends on whether absolute or
degree-normalized payoffs are used. We find that degree-normalized payoffs
require high-degree nodes be punished more lenient than low-degree nodes.
Conversely, if absolute payoffs count, then high-degree nodes should be
punished stronger than low-degree nodes.Comment: 19 pages, 8 figures; accepted for publication in Frontiers in
Behavioral Neuroscienc
A double-edged sword: Benefits and pitfalls of heterogeneous punishment in evolutionary inspection games
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.Comment: 9 two-column pages, 5 figures; accepted for publication in Scientific
Report
Costly hide and seek pays: Unexpected consequences of deceit in a social dilemma
Deliberate deceptiveness intended to gain an advantage is commonplace in
human and animal societies. In a social dilemma, an individual may only pretend
to be a cooperator to elicit cooperation from others, while in reality he is a
defector. With this as motivation, we study a simple variant of the
evolutionary prisoner's dilemma game entailing deceitful defectors and
conditional cooperators that lifts the veil on the impact of such two-faced
behavior. Defectors are able to hide their true intentions at a personal cost,
while conditional cooperators are probabilistically successful at identifying
defectors and act accordingly. By focusing on the evolutionary outcomes in
structured populations, we observe a number of unexpected and counterintuitive
phenomena. We show that deceitful behavior may fare better if it is costly, and
that a higher success rate of identifying defectors does not necessarily favor
cooperative behavior. These results are rooted in the spontaneous emergence of
cycling dominance and spatial patterns that give rise to fascinating phase
transitions, which in turn reveal the hidden complexity behind the evolution of
deception.Comment: 16 pages, 8 figures; accepted for publication in New Journal of
Physic
Vortices determine the dynamics of biodiversity in cyclical interactions with protection spillovers
If rock beats scissors and scissors beat paper, one might assume that rock
beats paper too. But this is not the case for intransitive relationships that
make up the famous rock-paper-scissors game. However, the sole presence of
paper might prevent rock from beating scissors, simply because paper beats
rock. This is the blueprint for the rock-paper-scissors game with protection
spillovers, which has recently been introduced as a new paradigm for
biodiversity in well-mixed microbial populations. Here we study the game in
structured populations, demonstrating that protection spillovers give rise to
spatial patterns that are impossible to observe in the classical
rock-paper-scissors game. We show that the spatiotemporal dynamics of the
system is determined by the density of stable vortices, which may ultimately
transform to frozen states, to propagating waves, or to target waves with
reversed propagation direction, depending further on the degree and type of
randomness in the interactions among the species. If vortices are rare, the
fixation to waves and complex oscillatory solutions is likelier. Moreover,
annealed randomness in interactions favors the emergence of target waves, while
quenched randomness favors collective synchronization. Our results demonstrate
that protection spillovers may fundamentally change the dynamics of cyclic
dominance in structured populations, and they outline the possibility of
programming pattern formation in microbial populations.Comment: 17 pages, 9 figures; accepted for publication in New Journal of
Physic
Antisocial pool rewarding does not deter public cooperation
Rewarding cooperation is in many ways expected behaviour from social players.
However, strategies that promote antisocial behaviour are also surprisingly
common, not just in human societies, but also among eusocial insects and
bacteria. Examples include sanctioning of individuals who behave prosocially,
or rewarding of freeriders who do not contribute to collective enterprises. We
therefore study the public goods game with antisocial and prosocial pool
rewarding in order to determine the potential negative consequences on the
effectiveness of positive incentives to promote cooperation. Contrary to a
naive expectation, we show that the ability of defectors to distribute rewards
to their like does not deter public cooperation as long as cooperators are able
to do the same. Even in the presence of antisocial rewarding the spatial
selection for cooperation in evolutionary social dilemmas is enhanced. Since
the administration of rewards to either strategy requires a considerable degree
of aggregation, cooperators can enjoy the benefits of their prosocial
contributions as well as the corresponding rewards. Defectors when aggregated,
on the other hand, can enjoy antisocial rewards, but due to their lack of
contributions to the public good they ultimately succumb to their inherent
inability to secure a sustainable future. Strategies that facilitate the
aggregation of akin players, even if they seek to promote antisocial behaviour,
thus always enhance the long-term benefits of cooperation.Comment: 9 two-column pages, 5 figures; accepted for publication in
Proceedings of the Royal Society
Leaders should not be conformists in evolutionary social dilemmas
The most common assumption in evolutionary game theory is that players should
adopt a strategy that warrants the highest payoff. However, recent studies
indicate that the spatial selection for cooperation is enhanced if an
appropriate fraction of the population chooses the most common rather than the
most profitable strategy within the interaction range. Such conformity might be
due to herding instincts or crowd behavior in humans and social animals. In a
heterogeneous population where individuals differ in their degree, collective
influence, or other traits, an unanswered question remains who should conform.
Selecting conformists randomly is the simplest choice, but it is neither a
realistic nor the optimal one. We show that, regardless of the source of
heterogeneity and game parametrization, socially the most favorable outcomes
emerge if the masses conform. On the other hand, forcing leaders to conform
significantly hinders the constructive interplay between heterogeneity and
coordination, leading to evolutionary outcomes that are worse still than if
conformists were chosen randomly. We conclude that leaders must be able to
create a following for network reciprocity to be optimally augmented by
conformity. In the opposite case, when leaders are castrated and made to
follow, the failure of coordination impairs the evolution of cooperation.Comment: 7 two-column pages, 4 figures; accepted for publication in Scientific
Reports [related work available at arXiv:1412.4113
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