Prof. Lars-Erik Cederman Center for Comparative and International Studies (CIS) Seilergraben 49, Room G.2, Nils Weidmann, Room E.3, Lecture, October 26, 2004 Introduction to Computational Modeling of Social Systems Examples of agent-based models in the social sciences

2 Today’s agenda Sample runs of simple models More complex models Where to find more models Gearing up

3 Simple sample models 1.Schelling’s segregation modelRePast 2.Traffic simulationNetLogo 3.AIDSNetLogo 4.SugerscapeAscape 5.Labour Market SimulationRePast

4 Example 1: Neighborhood segregation Thomas C. Schelling Micromotives and Macrobehavior < 1/3 Micro-level rules of the game Stay if at least a third of neighbors are “kin” Move to random location otherwise

5 Example 2: Traffic simulation (NetLogo) Model of the movement of cars on a highway Each car follows a simple set of rules: –if there’s car close ahead, it slows down –if there’s no car ahead, it speeds up The project demonstrates how traffic jams form spontaneously without obstacles

6 Example 3: AIDS (NetLogo) Simulate the spread of the human immunodeficiency virus (HIV), via sexual transmission Control of the –population's tendency to practice abstinence –amount of time an average "couple" in the population will stay together –population's tendency to use condoms –population's tendency to get tested for HIV

7 Example 4: Sugarscape (Ascape) Series of models introduced by Epstein and Axtell 1996 Growing Artificial Societies MIT Press Emergent features: –wealth distributions –social networks –migration –population dynamics –conflict patterns –price formation –credit networks Programmed in Ascape

8 Example 5: Labour Market Agents represent workers in an international labour market Agents’ main goal is to have a job and friends Jobs are available according to a country’s economic situation If the agent has been unhappy for a certain time period, it moves to another country (Model developed by Pedro Thomi as SS04 CompModels term project)

9 Complex sample models 1.Anasazi village formation 2.Nationalist insurgencies in Geosim 3.UrbanSim 4.ILUTE

10 Example 1: Anasazi Village Formation Gumerman et al SFI Working Paper (among others) Reconstruction of settlement patterns and demographics of pueblo Indians in the American Southwest The main puzzle pertains to the group’s sudden disappearance Based on the Sugarscape model, and thus also programmed in Ascape

11 Example 2: Geosim Geopolitical simulation system Cederman 2004 “Articulating the Mechanisms of Nationalist Insurgencies” Based on RePast ##44#2# National identities Cultural map State system Territorial obstacles

12 Example 3: UrbanSim UrbanSim is a simulation model for integrated planning and analysis Developed at the Univ. of Washington, Seattle Features decision-making by households, businesses, developers and governments

13 Example 4: ILUTE Integrated Land Use Transportation Modeling from Toronto

14 ILUTE continued

15 ILUTE continued

16 Where to find more models: Links See “Resources” under class home page Santa Fe Institute: Center for the Study of Complex Systems at the University of Michigan: European web sites on Computer simulation of societies and “European Social Simulation Association” For the US counterpart, see Leigh Tesfatsions’s site on computational economics: See also the Journal of Artificial Societies and Social Simulation:

17 Gearing up Installing the Java 2 SDK Installing IntelliJ IDEA Create the main project definition Create and run a simple test program Adding the RePast module (and optionally Ascape and NetLogo) Setting up Schelling’s segregation model (depends on RePast)

18 Development Environment int a = 12; if (a == b) b++; else a++; Java source code Editor Java compiler Java libs Integrated Development Environment e.g. IDEA JVM Repast libs