On Partially Controlled Multi-Agent Systems

Motivated by the control theoretic distinction between controllable and uncontrollable events, we distinguish between two types of agents within a multi-agent system: controllable agents, which are directly controlled by the system's designer, and uncontrollable agents, which are not under the designer's direct control. We refer to such systems as partially controlled multi-agent systems, and we investigate how one might influence the behavior of the uncontrolled agents through appropriate design of the controlled agents. In particular, we wish to understand which problems are naturally described in these terms, what methods can be applied to influence the uncontrollable agents, the effectiveness of such methods, and whether similar methods work across different domains. Using a game-theoretic framework, this paper studies the design of partially controlled multi-agent systems in two contexts: in one context, the uncontrollable agents are expected utility maximizers, while in the other they are reinforcement learners. We suggest different techniques for controlling agents' behavior in each domain, assess their success, and examine their relationship.Comment: See http://www.jair.org/ for any accompanying file

Games on Cellular Spaces: How Mobility Affects Equilibrium

In this work we propose a new model for spatial games. We present a definition of mobility in terms of the satisfaction an agent has with its spatial location. Agents compete for space through a non-cooperative game by using mixed strategies. We are particularly interested in studyig the relation between Nash equilibrium and the winner strategy of a given model with mobility, and how the mobility can affect the results. The experiments show that mobility is an important variable concerning spatial games. When we change parameters that affect mobility, it may lead to the success of strategies away from Nash equilibrium.Spatial Games, Agent-Based Modelling, Mobility, Satisfaction, Chicken Game, Nash Equilibrium

Agent Based Modeling of Electronic Markets To Analyze the Sustainability of Mutual Cooperation

According to game theory, dominant strategy of Prisoner’s Dilemma game is defecting. Since online trading between two strangers falls in the realm of a Prisoner’s Dilemma, failure should be the only logical conclusion of such electronic commerce situation. Traders are less likely to cooperate since they are not required to deal with the same buyer again given the enormous population of online traders. Thus one could argue that markets like eBay should never exist. Then what is the reason behind resounding success of such electronic markets? The answer lies in the reputation system that they established. Google page rankings and reader reviews on various sites like Amazon.com and Epinions.com are some other examples of the reputation system pointing towards the enormous influence that they wield in our everyday life. This research thus attempts to analyze importance of reputation system in an online trading using Agent Based Simulation. The effect of reputation system on the sustainability of mutual cooperation between online traders is analyzed by taking into account key factors like level of gullibility of online traders and the weight of influence given to their past behavior. Results indicate that reputation system is certainly capable of sustaining cooperation among online traders. However, weightage given to the past behavior of agents should be decided only after taking into account the level of gullibility of agents. Use of agent based modeling for studying dynamics of online trading is a relatively new concept. Sustaining cooperation among online traders is often perceived to be difficult task. The reputation system proposed in this research is expected to make contribution towards this goal

THE EFFECTS OF FEEDBACK ON COOPERATION IN THE PRISONER’S DILEMMA GAME SIMULATING A CLOSED MARKET SCENARIO

This study explores the effects of feedback on cooperation in the iterated prisoner’s dilemma game (PDG). Four sources of feedback were identified: peer, buyer, market and cultural feedback. Peer and buyer feedback were intrinsic to the PDG, for they were analyzed, but not manipulated. Market and cultural feedback comprised independent variables and their effects were measured on players’ and group cooperation (dependent variables). Twenty-seven participants played a PDG, divided in 9 groups of 3 players each. Cooperation was measured as rates of individual players’ cooperative X choices, and as aggregate products within groups. At the molecular (moment-to-moment) level, there was a significant within-subjects main effect of the market feedback F(1, 28) = 6.50, p = .02, ?p2 = .19. At the molar level, there was no significant effect of the market feedback, nor of the cultural feedback. It was not possible to establish a metacontingency between recurrent group cooperation and positive contingent group consequences. Players displayed sub-optimal choice behavior, seeking to maximize relative earnings within their group (defecting) over absolute earnings (cooperating). These results are discussed in light of how the source of feedback may sustain cooperation or defection in the PDG, and their implications in organizational settings. Reinforcing cooperative behaviors can be key to the maintenance and development of any organization, for informative performance feedback may not suffice. This study contributes to the understanding of economic decisional behavior in groups from a cultural selectionist perspective.Keywords: choice, cooperation, feedback, metacontingency, prisoner’s dilemma gameThis study explores the effects of feedback on cooperation in the iterated prisoner’s dilemma game (PDG). Four sources of feedback were identified: peer, buyer, market and cultural feedback. Peer and buyer feedback were intrinsic to the PDG, for they were analyzed, but not manipulated. Market and cultural feedback comprised independent variables and their effects were measured on players’ and group cooperation (dependent variables). Twenty-seven participants played a PDG, divided in 9 groups of 3 players each. Cooperation was measured as rates of individual players’ cooperative X choices, and as aggregate products within groups. At the molecular (moment-to-moment) level, there was a significant within-subjects main effect of the market feedback F(1, 28) = 6.50, p = .02, ?p2 = .19. At the molar level, there was no significant effect of the market feedback, nor of the cultural feedback. It was not possible to establish a metacontingency between recurrent group cooperation and positive contingent group consequences. Players displayed sub-optimal choice behavior, seeking to maximize relative earnings within their group (defecting) over absolute earnings (cooperating). These results are discussed in light of how the source of feedback may sustain cooperation or defection in the PDG, and their implications in organizational settings. Reinforcing cooperative behaviors can be key to the maintenance and development of any organization, for informative performance feedback may not suffice. This study contributes to the understanding of economic decisional behavior in groups from a cultural selectionist perspective.Keywords: choice, cooperation, feedback, metacontingency, prisoner’s dilemma gam

Game theory

Game theory was developed as a tool for rational decision-making. Its basic concepts were later used in evolutionary game theory to describe the evolution of behavioral phenotypes. In the hands of evolutionary biologists, this merger of game theory and population dynamics became an important tool for analysing frequency-dependent selection and social interaction

Leave and let leave: A sufficient condition to explain the evolutionary emergence of cooperation

The option to leave your current partner in response to his behavior, also known as conditional dissociation, is a mechanism that has been shown to promote the emergence and stability of cooperation in many social interactions. This mechanism, nevertheless, has always been studied in combination with other factors that are known to support cooperation by themselves. In this paper, we isolate the effect of conditional dissociation on the evolution of cooperation and show that this mechanism is enough to sustain a significant level of cooperation if the expected lifetime of individuals is sufficiently longACCESS (EU, 12-120610), SIMULPAST (MICINN, CSD2010-00034) and SPPORT (JCyL, VA056A12-2). L.R.I. Spanish Ministry of Education for grant JC2009-0026

The Viability of Cooperation Based on Interpersonal Commitment

A prominent explanation of cooperation in repeated exchange is reciprocity (e.g. Axelrod, 1984). However, empirical studies indicate that exchange partners are often much less intent on keeping the books balanced than Axelrod suggested. In particular, there is evidence for commitment behavior, indicating that people tend to build long-term cooperative relationships characterised by largely unconditional cooperation, and are inclined to hold on to them even when this appears to contradict self-interest. Using an agent-based computational model, we examine whether in a competitive environment commitment can be a more successful strategy than reciprocity. We move beyond previous computational models by proposing a method that allows to systematically explore an infinite space of possible exchange strategies. We use this method to carry out two sets of simulation experiments designed to assess the viability of commitment against a large set of potential competitors. In the first experiment, we find that although unconditional cooperation makes strategies vulnerable to exploitation, a strategy of commitment benefits more from being more unconditionally cooperative. The second experiment shows that tolerance improves the performance of reciprocity strategies but does not make them more successful than commitment. To explicate the underlying mechanism, we also study the spontaneous formation of exchange network structures in the simulated populations. It turns out that commitment strategies benefit from efficient networking: they spontaneously create a structure of exchange relations that ensures efficient division of labor. The problem with stricter reciprocity strategies is that they tend to spread interaction requests randomly across the population, to keep relations in balance. During times of great scarcity of exchange partners this structure is inefficient because it generates overlapping personal networks so that often too many people try to interact with the same partner at the same time.Interpersonal Commitment, Fairness, Reciprocity, Agent-Based Simulation, Help Exchange, Evolution

Expanding the theoretical and methodological framework of social dilemma research

Der Autor stellt fünf Anforderungen an die Entwicklung der theoretischen und methodischen Rahmens für die angewandte Forschung sozialer Dilemmata: (1) Die Untersuchung der Gründe eines beobachteten Verhaltens sollte sich nicht an subjektiven Kriterien zur Bewertung des Entscheidungsmusters orientieren; (2) Das experimentelle Design sollte stärker die Marktexperimente als die Spielexperimente betonen. Marktexperimente sollten besonders in Hinblick auf die Möglichkeit der dynamischen Ausrichtung untersucht werden, da die Rationalität eines Verhaltens empirisch meist nur dynamisch erfaßt werden kann. Diese Experimente sind einerseits theoretisch effizienter und andererseits ermöglichen sie die Beobachtung von Phänomenen, die sonst unentdeckt blieben; (3) Als Schlüsselelement für das Verständnis von Entscheidungen in sozialen Dilemma-Situationen sind die Erwartungen im Hinblick auf die Entscheidung anderer Akteure. Das Hauptaugenmerk in Experimenten sollte deshalb auf der Messung dieser Erwartungen der Subjekte liegen und die Rationalität dieser Erwartungen untersuchen; (4) Da der Endpunkt eines als rational zu bewertenden Ergebnisses ungewiß ist, kommt es auf den Prozeß selbst an, der die Rationalität der individuellen Entscheidugsfindung und die Marktdynamik in ein gewisses Gleichgewicht bringt. Die Untersuchung dieses Prozesses ist nur möglich, wenn der Konsens der einzelnen Akteure durch einen bargaining-Prozeß im Hinblick auf die Rationalität dieser bargaining-Strategien untersucht wird; (5) Die Annahme eir prozeß-orientierten Rationalität bedingt demnach die Analyse des bargaining-Verhaltens von Akteuren; das bedeutet, daß der Mittelpunkt der experimentellen Erforschung sozialer Dilemmata die Rekonstruktion der bargaining-Strategien, wie sie von den Akteuren angewandt worden sind, darstellen muß. Das gewählte experimentelle Design für diese Analyse sollten bargaining-Spiele zwischen realen Akteuren und einer anhand von Computersimulation erzeugten Gruppe von bargaining-Partnern sein. (HN Übers.)'In this paper five recommendations are given for expanding the theoretical and methodological framework of applied social dilemma research: 1.) We should not contend ourselves with identifying causal factors which may determine empirical subjects' decisions in social dilemmas. When looking for the ultimate causes of an observed behavior in social dilemmata, we have to explain the volutionary selection value of the decision patterns in questions; we must not contend ourselves with revealing the the psychic mechanisms which caused the observed behavior to happen. 2.) In designing our experiments, we should give more emphasis to experimental markets rather than to experimental games. In particular we should study experimental markets which allow for a dynamical adjustment, because quite often the rationality of a behavior can be empirically judged only from such a dynamical component. Such experiments will not only be theoretically richer, but will permit observing phenomena which would otherwise go undetected. 3.) The key to understanding peoble's decisions in social dilemmata are their expectations regarding the decisions of the other players. Therefore, a major focus of interest should be measuring these expectations of subjects in experiments, and investigating the rationality of these expectations. 4.) As soon as adjustment processes are no more equifinal (because there are many possible endpoints, which equally qualify as rational results) the rationality of individual decision making as well as of the market dynamics as a whole lies in the process itself of reaching some equilibrium. If we mean by bargaining any process by which individual players come to a convergende of wishes and offerings, then scutinizing the rationality of the bargaining strategies which on the marketplace the agents apply is the only way to investigate the rationality of the results of the whole process. 5.) Once we adopt a process oriented notion of rationality, as outlined, we have to put the analysis of our subjects' bargaining behavior, which means the reconstruction of the bargaining strategies, applied by the players, into the center stage of experimental social dilemma research. The experimental design of choice for this analysis are bargaining games between a real subject and a groupt of computer simulated bargaining partners.' (author's abstract

A complexidade da cooperação climática internacional

Although there are several collective efforts to address the problem of climate change, the main initiatives, such as the Kyoto Protocol and the Paris Agreement, have not shown satisfactory results so far. The difficulty in engaging states into effective coordinated cooperative practices can be explained as a consequence of neoclassical rationality, given that the characterization of states as rationality-endowed entities bound them to situations like the Prisoners' Dilemma (PD) game and its related collective action dilemmas. There are models that provide ways to circumvent PD and foster cooperation among selfish rational agents, such as the application of strategies based on reciprocity (Tit-for-Tat) in iterated games. However, these approaches do not avoid the short-sighted neoclassical rationality that lies at the root of the problem. Thus, in order to develop more productive approaches to the development of global climate change policies, I present a characterization of the international political system as a complex adaptive system (CAS) and argue that this perspective, along with models based on evolutionary games rather than iterated games, provide a more promising approach.Embora existam vários esforços coletivos para enfrentar o problema das mudanças climáticas, as principais iniciativas, como o Protocolo de Quioto e o Acordo de Paris, não têm apresentado resultados satisfatórios até o momento. A dificuldade em envolver os Estados em práticas cooperativas coordenadas efetivas pode ser explicada como consequência da racionalidade neoclássica, uma vez que a caracterização dos Estados como entidades dotadas de racionalidade os vincul a situações como o jogo do Dilema do Prisioneiro (DP), bem como os dilemas da ação coletiva relacionados a esse jogo. Existem modelos que fornecem maneiras de contornar o PD e promover a cooperação entre agentes racionais egoístas, como por exemplo a aplicação de estratégias baseadas na reciprocidade (Tit-for-Tat) em jogos iterados. No entanto, essas abordagens não evitam a racionalidade neoclássica de curto prazo, que está na raiz do problema. Assim, para desenvolver abordagens mais produtivas para o desenvolvimento de políticas globais para lidar com a mudança climática, apresento uma caracterização do sistema político internacional como um sistema adaptativo complexo (CAS) e argumento que essa perspectiva, acompanhada de modelos baseados em jogos evolutivos em vez de jogos iterados, fornece uma abordagem mais promissora