Coordination, Differentiation and Fairness in a population of cooperating agents

In a recent paper, we analyzed the self-assembly of a complex cooperation network. The network was shown to approach a state where every agent invests the same amount of resources. Nevertheless, highly-connected agents arise that extract extraordinarily high payoffs while contributing comparably little to any of their cooperations. Here, we investigate a variant of the model, in which highly-connected agents have access to additional resources. We study analytically and numerically whether these resources are invested in existing collaborations, leading to a fairer load distribution, or in establishing new collaborations, leading to an even less fair distribution of loads and payoffs.Comment: 10 pages, 3 figure

Price Rigidity and Strategic Uncertainty An Agent-based Approach

The phenomenon of infrequent price changes has troubled economists for decades. Intuitively one feels that for most price-setters there exists a range of inaction, i.e. a substantial measure of the states of the world, within which they do not wish to modify prevailing prices. However, basic economics tells us that when marginal costs change it is rational to change prices, too. Economists wishing to maintain rationality of price-setters resorted to fixed price adjustment costs as an explanation for price rigidity. In this paper we propose an alternative explanation, without recourse to any sort of physical adjustment cost, by putting strategic interaction into the center-stage of our analysis. Price-making is treated as a repeated oligopoly game. The traditional analysis of these games cannot pinpoint any equilibrium as a reasonable "solution" of the strategic situation. Thus there is genuine strategic uncertainty, a situation where decision-makers are uncertain of the strategies of other decision-makers. Hesitation may lead to inaction. To model this situation we follow the style of agent-based models, by modelling firms that change their pricing strategies following an evolutionary algorithm. Our results are promising. In addition to reproducing the known negative relationship between price rigidity and the level of general inflation, our model exhibits several features observed in real data. Moreover, most prices fall into the theoretical "range" without explicitly building this property into strategies.Agent-based modeling, Evolutionary algorithm, Price rigidity, Social learning, Strategic Uncertainty

The collapse of cooperation: The endogeneity of institutional break-up and its asymmetry with emergence

Decline and break-up of institutionalized cooperation, at all levels, has occurred frequently. Some of its concomitants, such as international migration, have become topical in the globalized world. Aspects of the phenomenon have also become known as failing states. However, the focus in most social sciences has been on institutional emergence and persistence, not collapse. We develop an endogenous explanation of collapsing institutions. Collapse may be an implication of the very economic success of institutionalized cooperation and of increasing system complexity, when cognitive conditions for effective collective decision-making do not proportionately evolve. Moreover, we show that collapse is not a simple logical reverse of emergence. Rather, institutions break up at different factor constellations than the ones prevailing at emergence. We approach endogenous institutional break-up and its asymmetry from various paradigmatic and disciplinary perspectives, employing psychology, anthropology, network analysis, and institutional economics. These perspectives cover individuals, groups, interaction-arenas, populations, and social networks

Social dynamics and cooperation: The case of nonhuman primates and its implications for human behavior.

The social factors that influence cooperation have remained largely uninvestigated but have the potential to explain much of the variation in cooperative behavior observed in the natural world. We show here that certain dimensions of the social environment, namely the size of the social group, the degree of social tolerance expressed, the structure of the dominance hierarchy, and the patterns of dispersal, may influence the emergence and stability of cooperation in predictable ways. Furthermore, the social environment experienced by a species over evolutionary time will have shaped their cognition to provide certain strengths and strategies that are beneficial in their species' social world. These cognitive adaptations will in turn impact the likelihood of cooperating in a given social environment. Experiments with one primate species, the cottontop tamarin, illustrate how social dynamics may influence emergence and stability of cooperative behavior in this species. We then take a more general viewpoint and argue that the hypotheses presented here require further experimental work and the addition of quantitative modeling to obtain a better understanding of how social dynamics influence the emergence and stability of cooperative behavior in complex systems. We conclude by pointing out subsequent specific directions for models and experiments that will allow relevant advances in the understanding of the emergence of cooperation.Ángel Sánchez was partially supported by Ministerio de Economía y Competitividad (Spain) through grants MOSAICO, PRODIEVO and Complexity-NET RESINEE, and by Comunidad de Madrid (Spain) through grant MODELICO-CM.Publicad

The importance of selection rate in the evolution of cooperation

8 pages, 4 figures.-- ArXiv pre-print available at: http://arxiv.org/abs/q-bio/0512045Final publisher version available Open Access at: http://gisc.uc3m.es/~cuesta/papers-year.htmlHow cooperation emerges in human societies is still a puzzle. Evolutionary game theory has been the standard framework to address this issue. In most models, every individual plays with all others, and then reproduces and dies according to what she earns. This amounts to assuming that selection takes place at a slow pace with respect to the interaction time scale. We show that, quite generally, if selection speeds up, the evolution outcome changes dramatically. Thus, in games such as Harmony, where cooperation is the only equilibrium and the only rational outcome, rapid selection leads to dominance of defectors. Similar non trivial phenomena arise in other binary games and even in more complicated settings such as the Ultimatum game. We conclude that the rate of selection is a key element to understand and model the emergence of cooperation, and one that has so far been overlooked.This work is supported by MEC (Spain) under grants BFM2003-0180, BFM2003-07749-C05-01, FIS2004-1001 and NAN2004-9087-C03-03 and by Comunidad de Madrid (Spain) under grants UC3M-FI-05-007, SIMUMAT-CM and MOSSNOHO-CM.Publicad

Shared water resources in decentralized city regions:mixed governance arrangements in Indonesia

This paper investigates emerging models of governance for shared water resources in decentralized urban regions in Indonesia and draws on a case of inter-local government collaboration for shared water resources in Cirebon region, Indonesia. The paper points to cooperation practice involving a mixed-model of governance for sharing water. by identifying a series of requirements for mixed governance. This model suits well not only because of the regional nature of water resource management in general, but also because such a model is likely to strengthen trust, increase transparency, and provide more equal positions among regions or stakeholders involved. Crucially, this model tends to decrease problematic levels of local autonomy and inter-local rivalry, which currently appears as a major challenge for shared water resource cooperation attempts in the decentralizing contexts of Indonesia and beyond

Evolutionary game theory: Temporal and spatial effects beyond replicator dynamics

Evolutionary game dynamics is one of the most fruitful frameworks for studying evolution in different disciplines, from Biology to Economics. Within this context, the approach of choice for many researchers is the so-called replicator equation, that describes mathematically the idea that those individuals performing better have more offspring and thus their frequency in the population grows. While very many interesting results have been obtained with this equation in the three decades elapsed since it was first proposed, it is important to realize the limits of its applicability. One particularly relevant issue in this respect is that of non-mean-field effects, that may arise from temporal fluctuations or from spatial correlations, both neglected in the replicator equation. This review discusses these temporal and spatial effects focusing on the non-trivial modifications they induce when compared to the outcome of replicator dynamics. Alongside this question, the hypothesis of linearity and its relation to the choice of the rule for strategy update is also analyzed. The discussion is presented in terms of the emergence of cooperation, as one of the current key problems in Biology and in other disciplines.Comment: Review, 48 pages, 26 figure