Introduction to Computational Modeling of Social Systems Prof

Introduction to Computational Modeling of Social Systems Prof. Lars-Erik Cederman ETH - Center for Comparative and International Studies (CIS) Seilergraben 49, Room G. 2, lcederman@ethz. ch Christa Deiwiks, CIS Room E. 3, deiwiks@icr. gess. ethz. ch http: //www. icr. ethz. ch/teaching/compmodels Week 1

Today’s agenda • Introduction – Course goals – Course contents • Course logistics – Prerequisites and grading – Schedule – Web. CT teaching system • Examples of agent-based models – Simple models: Schelling, Traffic, AIDS, Sugarscape – Complex models: Anasazi, Geosim 2

Course goals • • • Become familiar with the paradigm Advance your programming skills in Java Master Re. Past libraries Construct a simple computational model Start to think about how to apply the method to your own research puzzle 3

Course contents • Short Java Primer • Introduction to the principles of agentbased modeling • Introduction to Re. Past modeling • In SS 2007 there will be an advanced course extending this introductory lecture 4

Course logistics • Prerequisites: Programming experience (preferably in an object-oriented language) • Grading: – Four sets of exercises – To be completed through the Web. CT online teaching system • Resources: – Course web page http: //www. icr. ethz. ch/teaching/compmodels/ – …where you‘ll find the link to Web. CT: https: //aai-portal. ethz. ch/aai_portal/user/aai/login. php? rid=286. 347 FEAED 5 A 5

The Web. CT online teaching system 6

Course schedule • • • • October 24: Introduction Examples of agent-based models in the social sciences October 31: Java Primer / Gearing up November 7: Principles of agent-based modeling November 14: A hand-crafted agent-based model November 21: The Iterated Prisoner’s Dilemma and Re. Past Tutorial I November 28: Re. Past Tutorial II December 5: Re. Past Tutorial III December 12: Re. Past Tutorial IV December 19: Emergent Network models January 9: Emergent Structure models January 16: Emergent Actor models, Geo. Contest January 23: Emergent Actor models II January 30: Emergent Actor models III, Geo. Contest Presentation 7

What is agent-based modeling? • ABM is a computational methodology that allows the analyst to create, analyze, and experiment with, artificial worlds populated by agents that interact in non-trivial ways • Different from other types of computational techniques: econometrics, numerical solution, global modeling, AI modeling 8

Disaggregated modeling If then else Inanimate agents Animate agents Observer Data Organizations of agents Artificial world 9

Java 10 • Conceived by Sun in the early 1990 s • Became the new standard for the web thanks to platform-independence ntax sy C syntax C++ object model

Modeling in Re. Past • “Recursive Porous Agent Simulation Toolkit” • Re. Past is an open-source software framework for creating agent-based simulations using the Java programming language • Initially developed by the Social Science Research Computing at the University of Chicago since January 2000: http: //repast. sourceforge. net • Modeled on Swarm but easier to use and better documented 11

Re. Past framework 12 Controlling simulations Displaying behavior Charting Managing parameters

General readings on agentbased modeling • Axelrod, Robert. 1997. The Complexity of Cooperation: Agent-Based Models of Competition and Collaboration. Princeton: Princeton University Press. • Casti, John L. 1997. Would-Be Worlds: How Simulation Is Changing the Frontiers of Science. New York: Wiley. • Cederman, Lars-Erik. 1997. Emergent Actors in World Politics: How States and Nations Develop and Dissolve. Princeton: Princeton University Press. • Epstein, Joshua M. and Robert Axtell. 1996. Growing Artificial Societies: Social Science From the Bottom Up. Cambridge, Mass. : MIT Press. • Holland, John H. 1995. Hidden Order: How Adaptation Builds Complexity. Reading, Mass. : Addison-Wesley. 13

Simple sample models 1. Schelling’s segregation model 2. Traffic simulation 3. AIDS Re. Past Net. Logo 14

Example 1: Neighborhood segregation Micro-level rules of the game Stay if at least a third of neighbors are “kin” < 1/3 Move to random location otherwise Thomas C. Schelling Micromotives and Macrobehavior 15

Example 2: Traffic simulation (Net. Logo) • 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 16

Example 3: AIDS (Net. Logo) • 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 17

Complex sample models 1. Anasazi village formation 2. Nationalist insurgencies in Geosim 18

Example 1: Anasazi Village Formation • Gumerman et al. 2002 SFI Working Paper 02 -16 -067 (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 19

Example 2: Geosim • Geopolitical simulation system • Cederman (2004) “Articulating the Mechanisms of Nationalist Insurgencies” • Based on Re. Past 3##44#2# 32144421 • National identities • Cultural map • State system • Territorial obstacles 20

Where to find more models: Links • See “Resources” under class home page • Santa Fe Institute: http: //www. santafe. edu/ • Center for the Study of Complex Systems at the University of Michigan: http: //www. pscs. umich. edu/ • European web sites on Computer simulation of societies http: //www. soc. surrey. ac. uk/research/simsoc/ and “European Social Simulation Association” http: //essa. eu. org/ • For the US counterpart, see http: //www. casos. cmu. edu/naacsos/ • Leigh Tesfatsions’s site on computational economics: http: //www. econ. iastate. edu/tesfatsi/ace. htm • See also the Journal of Artificial Societies and Social Simulation: http: //jasss. soc. surrey. ac. uk/JASSS. html 21