4,313 research outputs found
Adaptive long-range migration promotes cooperation under tempting conditions
Migration is a fundamental trait in humans and animals. Recent studies
investigated the effect of migration on the evolution of cooperation, showing
that contingent migration favors cooperation in spatial structures. In those
studies, only local migration to immediate neighbors was considered, while
long-range migration has not been considered yet, partly because the long-range
migration has been generally regarded as harmful for cooperation as it would
bring the population to a well-mixed state that favors defection. Here, we
studied the effects of adaptive long-range migration on the evolution of
cooperation through agent-based simulations of a spatial Prisoner's Dilemma
game where individuals can jump to a farther site if they are surrounded by
more defectors. Our results show that adaptive long-range migration strongly
promotes cooperation, especially under conditions where the temptation to
defect is considerably high. These findings demonstrate the significance of
adaptive long-range migration for the evolution of cooperation.Comment: 7 pages, 9 figure
Transitions between homophilic and heterophilic modes of cooperation
Cooperation is ubiquitous in biological and social systems. Previous studies
revealed that a preference toward similar appearance promotes cooperation, a
phenomenon called tag-mediated cooperation or communitarian cooperation. This
effect is enhanced when a spatial structure is incorporated, because space
allows agents sharing an identical tag to regroup to form locally cooperative
clusters. In spatially distributed settings, one can also consider migration of
organisms, which has a potential to further promote evolution of cooperation by
facilitating spatial clustering. However, it has not yet been considered in
spatial tag-mediated cooperation models. Here we show, using computer
simulations of a spatial model of evolutionary games with organismal migration,
that tag-based segregation and homophilic cooperation arise for a wide range of
parameters. In the meantime, our results also show another evolutionarily
stable outcome, where a high level of heterophilic cooperation is maintained in
spatially well-mixed patterns. We found that these two different forms of
tag-mediated cooperation appear alternately as the parameter for temptation to
defect is increased.Comment: 16 pages, 7 figure
Dynamic aspiration based on Win-Stay-Lose-Learn rule in Spatial Prisoner's Dilemma Gam
Prisoner's dilemma game is the most commonly used model of spatial
evolutionary game which is considered as a paradigm to portray competition
among selfish individuals. In recent years, Win-Stay-Lose-Learn, a strategy
updating rule base on aspiration, has been proved to be an effective model to
promote cooperation in spatial prisoner's dilemma game, which leads aspiration
to receive lots of attention. But in many research the assumption that
individual's aspiration is fixed is inconsistent with recent results from
psychology. In this paper, according to Expected Value Theory and Achievement
Motivation Theory, we propose a dynamic aspiration model based on
Win-Stay-Lose-Learn rule in which individual's aspiration is inspired by its
payoff. It is found that dynamic aspiration has a significant impact on the
evolution process, and different initial aspirations lead to different results,
which are called Stable Coexistence under Low Aspiration, Dependent Coexistence
under Moderate aspiration and Defection Explosion under High Aspiration
respectively. Furthermore, a deep analysis is performed on the local structures
which cause cooperator's existence or defector's expansion, and the evolution
process for different parameters including strategy and aspiration. As a
result, the intrinsic structures leading to defectors' expansion and
cooperators' survival are achieved for different evolution process, which
provides a penetrating understanding of the evolution. Compared to fixed
aspiration model, dynamic aspiration introduces a more satisfactory explanation
on population evolution laws and can promote deeper comprehension for the
principle of prisoner's dilemma.Comment: 17 pages, 13 figure
Short-Range Mobility and the Evolution of Cooperation: An Experimental Study
A pressing issue in biology and social sciences is to explain how cooperation emerges in a population of self-interested individuals. Theoretical models suggest that one such explanation may involve the possibility of changing one's neighborhood by removing and creating connections to others, but this hypothesis has problems when random motion is considered and lacks experimental support. To address this, we have carried out experiments on diluted grids with human subjects playing a Prisoner's Dilemma. In contrast to previous results on purposeful rewiring in relational networks, we have found no noticeable effect of mobility in space on the level of cooperation. Clusters of cooperators form momentarily but in a few rounds they dissolve as cooperators at the boundaries stop tolerating being cheated upon. Our results highlight the difficulties that mobile agents have to establish a cooperative environment in a spatial setting.This work was supported by the Swiss National Science Foundation (under grant no.
200020-143224) and by the Rectors’ Conference of the Swiss Universities (under grant no. 26058983). This work has been supported in part by Ministerio de Economía y Competitividad (Spain) through grant PRODIEVO.Publicad
How L\'evy flights triggered by presence of defectors affect evolution of cooperation in spatial games
Cooperation among individuals has been key to sustaining societies. However,
natural selection favors defection over cooperation. Cooperation can be favored
when the mobility of individuals allows cooperators to form a cluster (or
group). Mobility patterns of animals sometimes follow a L\'evy flight. A L\'evy
flight is a kind of random walk but it is composed of many small movements with
a few big movements. The role of L\'evy flights for cooperation has been
studied by Antonioni and Tomassini. They showed that L\'evy flights promoted
cooperation combined with conditional movements triggered by neighboring
defectors. However, the optimal condition for neighboring defectors and how the
condition changes by the intensity of L\'evy flights are still unclear. Here,
we developed an agent-based model in a square lattice where agents perform
L\'evy flights depending on the fraction of neighboring defectors. We
systematically studied the relationships among three factors for cooperation:
sensitivity to defectors, the intensity of L\'evy flights, and population
density. Results of evolutionary simulations showed that moderate sensitivity
most promoted cooperation. Then, we found that the shortest movements were best
for cooperation when the sensitivity to defectors was high. In contrast, when
the sensitivity was low, longer movements were best for cooperation. Thus,
L\'evy flights, the balance between short and long jumps, promoted cooperation
in any sensitivity, which was confirmed by evolutionary simulations. Finally,
as the population density became larger, higher sensitivity was more beneficial
for cooperation to evolve. Our study highlights that L\'evy flights are an
optimal searching strategy not only for foraging but also for constructing
cooperative relationships with others.Comment: 8 pages, 5 figure
The Ecosystem Approach to Fisheries: Issues, Terminology, Principles, Institutional Foundations, Implementation and Outlook
Ecosystems are complex and dynamic natural units that produce goods and services beyond those of benefit to fisheries. Because fisheries have a direct impact on the ecosystem, which is also impacted by other human activities, they need to be managed in an ecosystem context. The meaning of the terms 'ecosystem management', 'ecosystem based management', 'ecosystem approach to fisheries'(EAF), etc., are still not universally defined and progressively evolving. The justification of EAF is evident in the characteristics of an exploited ecosystem and the impacts resulting from fisheries and other activities. The rich set of international agreements of relevance to EAF contains a large number of principles and conceptual objectives. Both provide a fundamental guidance and a significant challenge for the implementation of EAF. The available international instruments also provide the institutional foundations for EAF. The FAO Code of Conduct for Responsible Fisheries is particularly important in this respect and contains provisions for practically all aspects of the approach. One major difficulty in defining EAF lies precisely in turning the available concepts and principles into operational objectives from which an EAF management plan would more easily be developed. The paper discusses these together with the types of action needed to achieve them. Experience in EAF implementation is still limited but some issues are already apparent, e.g. in added complexity, insufficient capacity, slow implementation, need for a pragmatic approach, etc. It is argued, in conclusion, that the future of EAF and fisheries depends on the way in which the two fundamental concepts of fisheries management and ecosystem management, and their respective stakeholders, will join efforts or collide
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Trading in your spindles for blebs: the amoeboid tumor cell phenotype in prostate cancer
Prostate cancer (PCa) remains a principal cause of mortality in developed countries. Because no clinical interventions overcome resistance to androgen ablation therapy, management of castration resistance and metastatic disease remains largely untreatable. Metastasis is a multistep process in which tumor cells lose cell-cell contacts, egress from the primary tumor, intravasate, survive shear stress within the vasculature and extravasate into tissues to colonize ectopic sites. Tumor cells reestablish migratory behaviors employed during nonneoplastic processes such as embryonic development, leukocyte trafficking and wound healing. While mesenchymal motility is an established paradigm of dissemination, an alternate, ‘amoeboid’ phenotype is increasingly appreciated as relevant to human cancer. Here we discuss characteristics and pathways underlying the phenotype, and highlight our findings that the cytoskeletal regulator DIAPH3 governs the mesenchymal-amoeboid transition. We also describe our identification of a new class of tumor-derived microvesicles, large oncosomes, produced by amoeboid cells and with potential clinical utility in prostate and other cancers
Great Minds Think Different: Preserving Cognitive Diversity in an Age of Gene Editing
It is likely that gene editing technologies will become viable in the current century. As scientists uncover the genetic contribution to personality traits and cognitive styles, parents will face hard choices. Some of these choices will involve trade‐offs from the standpoint of the individual's welfare, while others will involve trade‐offs between what is best for each and what is good for all. Although we think we should generally defer to the informed choices of parents about what kinds of children to create, we argue that decisions to manipulate polygenic psychological traits will be much more ethically complicated than choosing Mendelian traits like blood type. We end by defending the principle of regulatory parsimony, which holds that when legislation is necessary to prevent serious harms, we should aim for simple rules that apply to all, rather than micro‐managing parental choices that shape the traits of their children. While we focus on embryo selection and gene editing, our arguments apply to all powerful technologies which influence the development of children
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