http://jasss.soc.surrey.ac.uk Journal of Artificial Societies and Social Simulation: For the exploration and understanding of social processes by means of computer simulation en-GB Copyright Journal of Artificial Societies and Social Simulation 2009-11-01 epress@soc.surrey.ac.uk yearly 4 2009-11-01 http://jasss.soc.surrey.ac.uk/gifs/JASSS-small.jpg http://jasss.soc.surrey.ac.uk marco.janssen@asu.edu (Marco A. Janssen) Article http://jasss.soc.surrey.ac.uk/12/4/13.html Sat, 31 Oct 2009 12:00:00 +0000 Marco A. Janssen: A replication and analysis of the Artificial Anasazi model is presented. It is shown that the success of replicating historical data is based on two parameters that adjust the carrying capacity of the Long House Valley. Compared to population estimates equal to the carrying capacity the specific agent behavior contributes only a modest improvement of the model to fit the archaeological records. r.vidgen@unsw.edu.au (Julian Padget, Richard Vidgen, James Mitchell, Amy Marshall and Rick Mellor) Article http://jasss.soc.surrey.ac.uk/12/4/8.html Sat, 31 Oct 2009 12:00:00 +0000 Julian Padget, Richard Vidgen, James Mitchell, Amy Marshall and Rick Mellor: The idea of agents exploring a fitness landscape in which they seek to move from 'fitness valleys' to higher 'fitness peaks' has been presented by Kauffman in the NK and NKCS models. The NK model addresses single species while the NKCS extension illustrates coevolving species on coupled fitness landscapes. We describe an agent-based simulation (Sendero), built in Repast, of the NK and NKCS models. The results from Sendero are validated against Kauffman's findings for the NK and NKCS models. We also describe extensions to the basic model, including population dynamics and communication networks for NK, and directed graphs and variable change rates for NKCS. The Sendero software is available as open source under the BSD licence and is thus available for download and extension by the research community. acrooks2@gmu.edu (Andrew Crooks, Andrew Hudson-Smith and Joel Dearden) Article http://jasss.soc.surrey.ac.uk/12/4/10.html Sat, 31 Oct 2009 12:00:00 +0000 Andrew Crooks, Andrew Hudson-Smith and Joel Dearden: Urban models can be seen on a continuum between iconic and symbolic. Generally speaking, iconic models are physical versions of the real world at some scaled down representation, while symbolic models represent the system in terms of the way they function replacing the physical or material system by some logical and/or mathematical formulae. Traditionally iconic and symbolic models were distinct classes of model but due to the rise of digital computing the distinction between the two is becoming blurred, with symbolic models being embedded into iconic models. However, such models tend to be single user. This paper demonstrates how 3D symbolic models in the form of agent-based simulations can be embedded into iconic models using the multi-user virtual world of Second Life. Furthermore, the paper demonstrates Second Life's potential for social science simulation. To demonstrate this, we first introduce Second Life and provide two exemplar models; Conway's Game of Life, and Schelling's Segregation Model which highlight how symbolic models can be viewed in an iconic environment. We then present a simple pedestrian evacuation model which merges the iconic and symbolic together and extends the model to directly incorporate avatars and agents in the same environment illustrating how 'real' participants can influence simulation outcomes. Such examples demonstrate the potential for creating highly visual, immersive, interactive agent-based models for social scientists in multi-user real time virtual worlds. The paper concludes with some final comments on problems with representing models in current virtual worlds and future avenues of research. tetsushi77@gmail.com (Tetsushi Ohdaira and Takao Terano) Article http://jasss.soc.surrey.ac.uk/12/4/7.html Sat, 31 Oct 2009 12:00:00 +0000 Tetsushi Ohdaira and Takao Terano: In the research addressing the prisoner's dilemma game, the effectiveness and accountableness of the method allowing for the emergence of cooperation is generally discussed. The most well-known solutions for this question are memory based iteration, the tag used to distinguish between defector and cooperator, the spatial structure of the game and the either direct or indirect reciprocity. We have also challenged to approach the topic from a different point of view namely that temperate acquisitiveness in decision making could be possible to achieve cooperation. It was already shown in our previous research that the exclusion of the best decision had a remarkable effect on the emergence of an almost cooperative state. In this paper, we advance the decision of our former research to become more explainable by introducing the second-best decision. If that decision is adopted, players also reach an extremely high level cooperative state in the prisoner's dilemma game and also in that of extended strategy expression. The cooperation of this extended game is facilitated only if the product of two parameters is under the criticality. In addition, the applicability of our model to the problem in the real world is discussed. Matthias.Meyer@whu.edu (Matthias Meyer, Iris Lorscheid and Klaus G. Troitzsch) Article http://jasss.soc.surrey.ac.uk/12/4/12.html Sat, 31 Oct 2009 12:00:00 +0000 Matthias Meyer, Iris Lorscheid and Klaus G. Troitzsch: Social simulation is often described as a multidisciplinary and fast-moving field. This can make it difficult to obtain an overview of the field both for contributing researchers and for outsiders who are interested in social simulation. The Journal for Artificial Societies and Social Simulation (JASSS) completing its tenth year provides a good opportunity to take stock of what happened over this time period. First, we use citation analysis to identify the most influential publications and to verify characteristics of social simulation such as its multidisciplinary nature. Then, we perform a co-citation analysis to visualize the intellectual structure of social simulation and its development. Overall, the analysis shows social simulation both in its early stage and during its first steps towards becoming a more differentiated discipline. heath.brian@gmail.com (Brian Heath, Raymond Hill and Frank Ciarallo) Article http://jasss.soc.surrey.ac.uk/12/4/9.html Sat, 31 Oct 2009 12:00:00 +0000 Brian Heath, Raymond Hill and Frank Ciarallo: In the 1990s, Agent-Based Modeling (ABM) began gaining popularity and represents a departure from the more classical simulation approaches. This departure, its recent development and its increasing application by non-traditional simulation disciplines indicates the need to continuously assess the current state of ABM and identify opportunities for improvement. To begin to satisfy this need, we surveyed and collected data from 279 articles from 92 unique publication outlets in which the authors had constructed and analyzed an agent-based model. From this large data set we establish the current practice of ABM in terms of year of publication, field of study, simulation software used, purpose of the simulation, acceptable validation criteria, validation techniques and complete description of the simulation. Based on the current practice we discuss six improvements needed to advance ABM as an analysis tool. These improvements include the development of ABM specific tools that are independent of software, the development of ABM as an independent discipline with a common language that extends across domains, the establishment of expectations for ABM that match their intended purposes, the requirement of complete descriptions of the simulation so others can independently replicate the results, the requirement that all models be completely validated and the development and application of statistical and non-statistical validation techniques specifically for ABM. a.pyka@uni-hohenheim.de (Andreas Pyka and Claudia Werker) Article http://jasss.soc.surrey.ac.uk/12/4/1.html Sat, 31 Oct 2009 12:00:00 +0000 Andreas Pyka and Claudia Werker: Introduction to special section giuseppe.vizzari@disco.unimib.it (Stefania Bandini, Sara Manzoni and Giuseppe Vizzari) Article http://jasss.soc.surrey.ac.uk/12/4/4.html Sat, 31 Oct 2009 12:00:00 +0000 Stefania Bandini, Sara Manzoni and Giuseppe Vizzari: The term computer simulation is related to the usage of a computational model in order to improve the understanding of a system's behavior and/or to evaluate strategies for its operation, in explanatory or predictive schemes. There are cases in which practical or ethical reasons make it impossible to realize direct observations: in these cases, the possibility of realizing 'in-machina' experiments may represent the only way to study, analyze and evaluate models of those realities. Different situations and systems are characterized by the presence of autonomous entities whose local behaviors (actions and interactions) determine the evolution of the overall system; agent-based models are particularly suited to support the definition of models of such systems, but also to support the design and implementation of simulators. Agent-Based models and Multi-Agent Systems (MAS) have been adopted to simulate very different kinds of complex systems, from the simulation of socio-economic systems to the elaboration of scenarios for logistics optimization, from biological systems to urban planning. This paper discusses the specific aspects of this approach to modeling and simulation from the perspective of Informatics, describing the typical elements of an agent-based simulation model and the relevant research. a.pyka@uni-hohenheim.de (Simon Deichsel and Andreas Pyka) Article http://jasss.soc.surrey.ac.uk/12/4/6.html Sat, 31 Oct 2009 12:00:00 +0000 Simon Deichsel and Andreas Pyka: The issues of empirical calibration of parameter values and functional relationships describing the interactions between the various actors plays an important role in agent based modelling. Agent-based models range from purely theoretical exercises focussing on the patterns in the dynamics of interactions processes to modelling frameworks which are oriented closely at the replication of empirical cases. ABMs are classified in terms of their generality and their use of empirical data. In the literature the recommendation can be found to aim at maximizing both criteria by building so-called 'abductive models'. This is almost the direct opposite of Milton Friedman's famous and provocative methodological credo 'the more significant a theory, the more unrealistic the assumptions'. Most methodologists and philosophers of science have harshly criticised Friedman's essay as inconsistent, wrong and misleading. By presenting arguments for a pragmatic reinterpretation of Friedman's essay, we will show why most of the philosophical critique misses the point. We claim that good simulations have to rely on assumptions, which are adequate for the purpose in hand and those are not necessarily the descriptively accurate ones. c.werker@tudelft.nl (Thomas Brenner and Claudia Werker) Article http://jasss.soc.surrey.ac.uk/12/4/2.html Sat, 31 Oct 2009 12:00:00 +0000 Thomas Brenner and Claudia Werker: When advising policy we face the fundamental problem that economic processes are uncertain. Consequently, policy can err. In this paper we show how the use of simulation models can reduce policy errors by inferring empirically reliable and meaningful statements about economic processes. We suggest that policy is best based on so-called abductive simulation models, which help to better understand how policy measures can influence economic processes. We show that abductive simulation models use a combination of theoretical and empirical analysis based on different data sets. By way of example we show what policy can learn with the help of abductive simulation models, namely how policy measures can influence the emergence of a regional cluster. michael.neugart@unibz.it (Herbert Dawid, Simon Gemkow, Philipp Harting and Michael Neugart) Article http://jasss.soc.surrey.ac.uk/12/4/5.html Sat, 31 Oct 2009 12:00:00 +0000 Herbert Dawid, Simon Gemkow, Philipp Harting and Michael Neugart: We report results of economic policy experiments carried out in the framework of the EURACE agent-based macroeconomic model featuring a distinct geographical dimension and heterogeneous workers with respect to skill types. Using a calibrated model able to replicate a range of stylized facts of goods and labor markets, it is examined in how far effects differ if policy measures aiming at an improvement of general skills are uniformly spread over all regions in the economy or focused in one particular region. We find that it depends on the level of spatial frictions on the labor market how the spatial distribution of policy measures affects the effects of the policy. Furthermore, we show that a reduction in spatial frictions does not necessarily improve the growth of output and household income. g.yucel@tudelft.nl (Gnen Y and Els van Daalen) Article http://jasss.soc.surrey.ac.uk/12/4/3.html Sat, 31 Oct 2009 12:00:00 +0000 Gnen Y and Els van Daalen: Simulation models, being in use for a long time in natural sciences and engineering domains, are diffusing to a wider context including policy analysis studies. The differences between the nature of the domain of application, as well as the increased variety of usage partially induced by this difference naturally imply new challenges to be overcome. One of these challenges is related to the assessment of the simulation-based outcomes in terms of their reliability and relevance in the policy context being studied. The importance of this assessment is twofold. First of all, it is all about conducting a high quality policy study with effective results. However, the quality of the study does not necessarily imply acceptance of the results by the clients and/or colleagues. This problem of policy analysts increases the importance of such an assessment; an effective assessment may induce the acceptance of the conclusions drawn from the study by the clients and/or colleagues. The main objective of this paper is to introduce an objective-based assessment perspective for simulation model-supported policy studies. As a first step towards such a goal, an objective-based classification of models is introduced. Based on that, we will discuss the importance of different aspects of the assessment for each type. In doing so, we aim to provide a structured discussion that may serve as a sort of methodological guideline to be used by policy analysts, and also by clients. oliver.will@uni-bayreuth.de (Oliver Will) Article http://jasss.soc.surrey.ac.uk/12/4/11.html Sat, 31 Oct 2009 12:00:00 +0000 Oliver Will: The paper at hand aimes at identifying the assumptions that lead to the results presented in an article by Michael Macy and Yoshimichi Sato published in PNAS. In answer to a failed replication, the authors provided the source code of their model and here the results of carefully studying that code are presented. The main finding is that the simulation program implements an assumption that is most probably an unwilling, unintended, and unwanted implication of the code. This implied assumption is never mentioned in Macy and Sato's article and if the authors wanted to program what they describe in their article then it is due to a programming error. After introducing the reader to the discussion, data that stem from a new replication based on the assumptions extracted from the source code is compared with the results published in Macy and Sato's original article. The replicated results are sufficiently similar to serve as a strong indicator that this new replication implements the same relevant assumptions as the original model. Afterwards it is shown that a removal of the dubious assumption leads to results that are dramatically different from those published in Macy and Sato's PNAS article. tako@wsu.edu (Timothy Kohler) Review http://jasss.soc.surrey.ac.uk/12/4/reviews/kohler.html Sat, 31 Oct 2009 12:00:00 +0000 Review of: Advances in Complex Systems (ACS): Special Issue on Social Simulation, Vol. 11, No. 2 by Amblard, Frédéric, and Jager, Wander (Eds.), reviewed by Timothy Kohler martin.neumann@uni-bayreuth.de (Martin Neumann) Review http://jasss.soc.surrey.ac.uk/12/4/reviews/neumann.html Sat, 31 Oct 2009 12:00:00 +0000 Review of: Multi-Agent-Based Simulation IX (Lecture Notes in Computer Science / Lecture Notes in Artificial Intelligence) by David, Nuno and Paulo, Jaime Simao (eds.), reviewed by Martin Neumann posada@eis.uva.es (Marta Posada) Review http://jasss.soc.surrey.ac.uk/12/4/reviews/posada.html Sat, 31 Oct 2009 12:00:00 +0000 Review of: Rationality for Mortals: How People Cope with Uncertainty by Gigerenzer, Gerd, reviewed by Marta Posada r.corten@uu.nl (Rense Corten) Review http://jasss.soc.surrey.ac.uk/12/4/reviews/corten.html Sat, 31 Oct 2009 12:00:00 +0000 Review of: Game Theory Evolving: A Problem-Centered Introduction to Modeling Strategic Interaction (Second Edition) by Gintis, Herbert, reviewed by Rense Corten gabrielistrate@acm.org (Gabriel Istrate) Review http://jasss.soc.surrey.ac.uk/12/4/reviews/istrate.html Sat, 31 Oct 2009 12:00:00 +0000 Review of: Computational Complexity: A Conceptual Perspective by Goldreich, Oded, reviewed by Gabriel Istrate petra.ahrweiler@ucd.ie (Petra Ahrweiler) Review http://jasss.soc.surrey.ac.uk/12/4/reviews/ahrweiler.html Sat, 31 Oct 2009 12:00:00 +0000 Review of: Complexity Perspectives in Innovation and Social Change (Methods Series) by Lane David, Pumain Denise, van der Leeuw Sander Ernst, West Geoffrey (Eds.), reviewed by Petra Ahrweiler ageller1@gmu.edu (Armando Geller) Review http://jasss.soc.surrey.ac.uk/12/4/reviews/geller.html Sat, 31 Oct 2009 12:00:00 +0000 Review of: Artificial Crime Analysis Systems: Using Computer Simulations and Geographic Information Systems by Liu, Lin and Eck, John (Eds.), reviewed by Armando Geller jsr1950@gmail.com (Roy Wilson) Review http://jasss.soc.surrey.ac.uk/12/4/reviews/wilson.html Sat, 31 Oct 2009 12:00:00 +0000 Review of: Epistemological Aspects of Computer Simulation in the Social Sciences (Lecture Notes in Computer Science) by Squazzoni, Flaminio (ed.), reviewed by Roy Wilson jbragin@ucla.edu (John Bragin) Review http://jasss.soc.surrey.ac.uk/12/4/reviews/bragin.html Sat, 31 Oct 2009 12:00:00 +0000 Review of: Handbook of Research on Agent-Based Societies: Social and Cultural Interactions by Trajkovski, Goran, Collins, Samuel G. (Eds.), reviewed by John Bragin Review http://jasss.soc.surrey.ac.uk/12/4/reviews/wilsonroy.html Sat, 31 Oct 2009 12:00:00 +0000 Review of: Simulation and Its Discontents by Turkle, Sherry, reviewed by WilsonRoy WilsonRoy marco.villani@unimore.it (Marco Villani) Review http://jasss.soc.surrey.ac.uk/12/4/reviews/villani.html Sat, 31 Oct 2009 12:00:00 +0000 Review of: Multi-Agent Systems. Simulation and Applications (Computational Analysis, Synthesis, and Design of Dynamic Models Series) by Uhrmacher, Adelinde M., Weyns, Danny and Mosterman, Pieter J. (Eds.), reviewed by Marco Villani