Luis R Izquierdo

La economía artificial es uno de los métodos o enfoques de investigación para el estudio de sistemas socioeconómicos complejos con mayor crecimiento durante los últimos años. Este artículo presenta una visión crítica sobre sus características, su potencial y los riesgos relativos al uso de esta metodología. Para ello, encontramos útil relacionar y comparar a la economía artificial con la economía teórica más tradicional. Desde nuestro análisis, la economía teórica y la economía artificial comparten los mismos objetivos, presentan menos diferencias metodológicas de las que a primera vista pudiera parecer, y sus aproximaciones son sin duda complementarias.

This paper describes EVO-2x2, a computer simulation modelling framework designed to formally investigate the evolution of strategies in 2-player 2-strategy (2x2) symmetric games under various competing assumptions. EVO- 2x2 enables the user to explore the implications of alternative assumptions (all of which are fully consistent with the essence of the theory of evolution) in a coherent and systematic way. It thus provides a single framework within which results obtained using different assumptions can be contrasted and compared with analytical approaches. We illustrate the usefulness of EVO-2x2 by studying the evolution of cooperation in the Prisoner's Dilemma under different settings. 1. Introduction This paper describes EVO-2x2, a computer simulation modelling framework designed to formally investigate the evolution of strategies in 2-player 2-strategy (2x2) symmetric games under various competing assumptions. EVO- 2x2 enables the user to set up and run many computer simulations (effectively many different models) aimed at investigating the same question from different angles. The specific question to be addressed is usually of the form: "In a population of individuals who interact with each other by repeatedly playing a certain 2x2 symmetric game, what strategies are likely to emerge and be sustained under evolutionary pressures?". Naturally, the answer to such a question may depend on a number of assumptions regarding population size, magnitude of payoffs, population structure, the implementation of the natural selection algorithm, and the mutation mechanism. EVO-2x2 enables the researcher to assess the impact of many such assumptions by providing a single coherent framework within which results obtained from different models can be contrasted and compared with analytical approaches. EVO-2x2 implements a wide range of competing plausible assumptions, all of which are fully consistent with the most basic principles of the theory of evolution. Thus, in broader terms, EVO-2x2 can be used to assess the extent to which the assumptions made in mainstream evolutionary game theory (Weibull, 1995) for the sake of tractability (e.g. infinite populations, random pairings, finite set of deterministic strategies, continuous time, and proportional fitness rule) are affecting its conclusions. This paper is divided into two parts: a description of EVO-2x2 (section 2) and an illustration of how EVO-2x2 can be used in practice (section 3). This latter section is focused on a study of the evolutionary emergence of cooperation among individuals playing the Prisoner's Dilemma.

In this paper we present a teaching methodology for introducing students to the mean-field approximation. We also include some teaching material –in the form of computer models– that academics may want to use in their own lectures. The methodology emphasises the value of teaching students the intuition underlying the mean-field approximation in a graphical and interactive way, with the help of purpose-built computer programs. As an illustrative example, we present a simple imitation model from the field of Game Theory, which we analyse combining the theory of Markov chains with the mean-field approximation.

The aim of this paper is to assist researchers in understanding the dynamics of simulation models that have been implemented and can be run in a computer, i.e. computer models. To do that, we start by explaining (a) that computer models are just input-output functions, (b) that every computer model can be re-implemented in many different formalisms (in particular in most programming languages), leading to alternative representations of the same input-output relation, and (c) that many computer models in the social simulation literature can be usefully represented as time-homogeneous Markov chains. Then we argue that analysing a computer model as a Markov chain can make apparent many features of the model that were not so evident before conducting such analysis. To prove this point, we present the main concepts needed to conduct a formal analysis of any time-homogeneous Markov chain, and we illustrate the usefulness of these concepts by analysing 10 well-known models in the social si...

Experimental Economists have designed over the years a wide range of scientific experiments that can be usefully employed nowadays as teaching aids. The interactive and participatory nature of such experiments serves as a motivation to students, stimulates their own thinking, and enhances their insights into the forces that drive economic markets: the aggregate interactions of economic agents within a market institution. Economic classroom games have been recognised as useful teaching tools for decades, and they have often produced surprising results and better understanding of market dynamics and institutions. Nowadays the new information technologies can be brought into play to conduct and analyse experimental games in unprecedented ways: using Internet-based tools, the design, execution and analysis of classroom games can be made considerably easier than traditionally. In this paper we introduce LABEXNET, a program designed to conduct Internet-based economic classroom games. LABE...

The objectives of this paper are to define and classify different types of errors and artefacts that can appear in the process of developing an agent-based model, and to propose activities aimed at avoiding them during the model construction and testing phases. To do this in a structured way, we review the main concepts of the process of developing such a model – establishing a general framework that summarises the process of designing, implementing, and using agent-based models. Within this framework we identify the various stages where different types of errors and artefacts may appear. Finally we propose activities that could be used to detect (and hence eliminate) each type of error or artefact.

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 long.