4,824 research outputs found
Competition and cooperation among different punishing strategies in the spatial public goods game
Inspired by the fact that people have diverse propensities to punish
wrongdoers, we study a spatial public goods game with defectors and different
types of punishing cooperators. During the game, cooperators punish defectors
with class-specific probabilities and subsequently share the associated costs
of sanctioning. We show that in the presence of different punishing cooperators
the highest level of public cooperation is always attainable through a
selection mechanism. Interestingly, the selection not necessarily favors the
evolution of punishers who would be able to prevail on their own against the
defectors, nor does it always hinder the evolution of punishers who would be
unable to prevail on their own. Instead, the evolutionary success of punishing
strategies depends sensitively on their invasion velocities, which in turn
reveals fascinating examples of both competition and cooperation among them.
Furthermore, we show that under favorable conditions, when punishment is not
strictly necessary for the maintenance of public cooperation, the less
aggressive, mild form of sanctioning is the sole victor of selection process.
Our work reveals that natural strategy selection can not only promote, but
sometimes also hinder competition among prosocial strategies.Comment: 6 two-column pages, 5 figures; accepted for publication in Physical
Review
Evolutionary establishment of moral and double moral standards through spatial interactions
Situations where individuals have to contribute to joint efforts or share
scarce resources are ubiquitous. Yet, without proper mechanisms to ensure
cooperation, the evolutionary pressure to maximize individual success tends to
create a tragedy of the commons (such as over-fishing or the destruction of our
environment). This contribution addresses a number of related puzzles of human
behavior with an evolutionary game theoretical approach as it has been
successfully used to explain the behavior of other biological species many
times, from bacteria to vertebrates. Our agent-based model distinguishes
individuals applying four different behavioral strategies: non-cooperative
individuals ("defectors"), cooperative individuals abstaining from punishment
efforts (called "cooperators" or "second-order free-riders"), cooperators who
punish non-cooperative behavior ("moralists"), and defectors, who punish other
defectors despite being non-cooperative themselves ("immoralists"). By
considering spatial interactions with neighboring individuals, our model
reveals several interesting effects: First, moralists can fully eliminate
cooperators. This spreading of punishing behavior requires a segregation of
behavioral strategies and solves the "second-order free-rider problem". Second,
the system behavior changes its character significantly even after very long
times ("who laughs last laughs best effect"). Third, the presence of a number
of defectors can largely accelerate the victory of moralists over non-punishing
cooperators. Forth, in order to succeed, moralists may profit from immoralists
in a way that appears like an "unholy collaboration". Our findings suggest that
the consideration of punishment strategies allows to understand the
establishment and spreading of "moral behavior" by means of game-theoretical
concepts. This demonstrates that quantitative biological modeling approaches
are powerful even in domains that have been addressed with non-mathematical
concepts so far. The complex dynamics of certain social behaviors becomes
understandable as result of an evolutionary competition between different
behavioral strategies.Comment: 15 pages, 5 figures; accepted for publication in PLoS Computational
Biology [supplementary material available at
http://www.soms.ethz.ch/research/secondorder-freeriders/ and
http://www.matjazperc.com/plos/moral.html
Effectiveness of conditional punishment for the evolution of public cooperation
Collective actions, from city marathons to labor strikes, are often mass-driven and subject to the snowball effect. Motivated by this, we study evolutionary advantages of conditional punishment in the spatial public goods game. Unlike unconditional punishers who always impose the same fines on defectors, conditional punishers do so proportionally with the number of other punishers in the group. Phase diagrams in dependence on the punishment fine and cost reveal that the two types of punishers cannot coexist. Spontaneous coarsening of the two strategies leads to an indirect territorial competition with the defectors, which is won by unconditional punishers only if the sanctioning is inexpensive. Otherwise conditional punishers are the victors of the indirect competition, indicating that under more realistic conditions they are indeed the more effective strategy. Both continuous and discontinuous phase transitions as well as tricritical points characterize the complex evolutionary dynamics, which is due to multipoint interactions that are introduced by conditional punishment. We propose indirect territorial competition as a generally applicable mechanism relying on pattern formation, by means of which spatial structure can be utilized by seemingly subordinate strategies to avoid evolutionary extinction
Sustainable institutionalized punishment requires elimination of second-order free-riders
Although empirical and theoretical studies affirm that punishment can elevate
collaborative efforts, its emergence and stability remain elusive. By
peer-punishment the sanctioning is something an individual elects to do
depending on the strategies in its neighborhood. The consequences of
unsustainable efforts are therefore local. By pool-punishment, on the other
hand, where resources for sanctioning are committed in advance and at large,
the notion of sustainability has greater significance. In a population with
free-riders, punishers must be strong in numbers to keep the "punishment pool"
from emptying. Failure to do so renders the concept of institutionalized
sanctioning futile. We show that pool-punishment in structured populations is
sustainable, but only if second-order free-riders are sanctioned as well, and
to a such degree that they cannot prevail. A discontinuous phase transition
leads to an outbreak of sustainability when punishers subvert second-order
free-riders in the competition against defectors.Comment: 7 two-column pages, 3 figures; accepted for publication in Scientific
Report
Correlation of Positive and Negative Reciprocity Fails to Confer an Evolutionary Advantage: Phase Transitions to Elementary Strategies
Economic experiments reveal that humans value cooperation and fairness. Punishing unfair behavior is therefore common, and according to the theory of strong reciprocity, it is also directly related to rewarding cooperative behavior. However, empirical data fail to confirm that positive and negative reciprocity are correlated. Inspired by this disagreement, we determine whether the combined application of reward and punishment is evolutionarily advantageous. We study a spatial public goods game, where in addition to the three elementary strategies of defection, rewarding, and punishment, a fourth strategy that combines the latter two competes for space. We find rich dynamical behavior that gives rise to intricate phase diagrams where continuous and discontinuous phase transitions occur in succession. Indirect territorial competition, spontaneous emergence of cyclic dominance, as well as divergent fluctuations of oscillations that terminate in an absorbing phase are observed. Yet, despite the high complexity of solutions, the combined strategy can survive only in very narrow and unrealistic parameter regions. Elementary strategies, either in pure or mixed phases, are much more common and likely to prevail. Our results highlight the importance of patterns and structure in human cooperation, which should be considered in future experiments
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
Understanding recurrent crime as system-immanent collective behavior
Containing the spreading of crime is a major challenge for society. Yet,
since thousands of years, no effective strategy has been found to overcome
crime. To the contrary, empirical evidence shows that crime is recurrent, a
fact that is not captured well by rational choice theories of crime. According
to these, strong enough punishment should prevent crime from happening. To gain
a better understanding of the relationship between crime and punishment, we
consider that the latter requires prior discovery of illicit behavior and study
a spatial version of the inspection game. Simulations reveal the spontaneous
emergence of cyclic dominance between ''criminals'', ''inspectors'', and
''ordinary people'' as a consequence of spatial interactions. Such cycles
dominate the evolutionary process, in particular when the temptation to commit
crime or the cost of inspection are low or moderate. Yet, there are also
critical parameter values beyond which cycles cease to exist and the population
is dominated either by a stable mixture of criminals and inspectors or one of
these two strategies alone. Both continuous and discontinuous phase transitions
to different final states are possible, indicating that successful strategies
to contain crime can be very much counter-intuitive and complex. Our results
demonstrate that spatial interactions are crucial for the evolutionary outcome
of the inspection game, and they also reveal why criminal behavior is likely to
be recurrent rather than evolving towards an equilibrium with monotonous
parameter dependencies.Comment: 9 two-column pages, 5 figures; accepted for publication in PLoS ON
Probabilistic sharing solves the problem of costly punishment
Cooperators that refuse to participate in sanctioning defectors create the
second-order free-rider problem. Such cooperators will not be punished because
they contribute to the public good, but they also eschew the costs associated
with punishing defectors. Altruistic punishers - those that cooperate and
punish - are at a disadvantage, and it is puzzling how such behaviour has
evolved. We show that sharing the responsibility to sanction defectors rather
than relying on certain individuals to do so permanently can solve the problem
of costly punishment. Inspired by the fact that humans have strong but also
emotional tendencies for fair play, we consider probabilistic sanctioning as
the simplest way of distributing the duty. In well-mixed populations the public
goods game is transformed into a coordination game with full cooperation and
defection as the two stable equilibria, while in structured populations pattern
formation supports additional counterintuitive solutions that are reminiscent
of Parrondo's paradox.Comment: 15 pages, 5 figures; accepted for publication in New Journal of
Physic
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