Multi-Agent Modeling of Societal Development and Cultural Evolution Yidan Chen, 2006 Computer Systems Research Lab

Abstract  The "bottom-up" approach  Implementing the background world and individualized agents with specific attributes  The Multi-Agent Simulator of Neighborhoods (MASON) library  Simple rules to regulate agent behavior  Agent-based simulations with correlating results to historically recorded migration developments  Complex behavior results through economic aspects of wealth distribution and trade, and social aspects of reproduction, death, health, and cultural exchange.

Scope  Initially limited to basic rules of survival (food/migration)  Incorporate the ideas of life and death into Sugarscape  Variable values for basic parameters  Implement more complex rules with time (intergroup relations/ disease)

Background1  Concept of life as Information  Research in areas of artificial life  Conway's Game of Life  First known case of artificial life  Finite initial configurations generate an infinite population  Complex implications from simple rules

Background 2  Implications of Conway's Life  Leads to bottom-up models of real world situations  Graig Reynolds's “boids”  Computational model of decentralized activity  Based on individual rules  No centralized control

Background 3  Robert Axtell & Joshua M. Epstein's Sugarscape  Simple rules cause aggregate effects  Based on interactions between Agents  Proto-history, cultural evolution, population development, etc.

World  Value of each cell corresponds to map  Sugar grows back with each step, rate dependent on growth rule 

Agents  Metabolism – Int between 1 & maxSugar  Vision – Int between 1 & 8  Collects all sugar in cell with each step  Moves to closest cell with highest sugar value

Methodology  Build on the algorithm of another program (Schelling and Heatbugs in MASON)  First prototype to duplicate growth rule (RuleG)  Duplicate simple agent functions (takeSugar, reaper, step)  Some other stuff that didn't happen

2D Representation  Agents represented by red circles  Sugar show in yellow  More yellow represents greater density

Testing  Agents start in square at top corner  Movement in waves towards other pole of sugar  Consistent

3D Representation  3D based off of HeatBug3DWithUI  Uses Java3D – remote does not work (applet)

Results 1  Initially migration pattern some error  Tendency to move back and forth in the horizontal direction, or a tendency to bypass closer cells with equal amounts of sugar.

Results 2  Implementation of a distance check in step() method  Agents start with randomly assigned positions  Pick the optimal position and continue to advance

Results 3  Sugar growthRate is a limited number {RuleG}  Agents all migrate to the poles  Agents form congregation at the center of the poles

Conclusion 1  The basic statistics recorded and displayed through the use of screen shots and graphs  The patterns of migration in the agents show interesting insight into progression of a population when a limited resource is in question.

Conclusion 2  When each member of a society acts for its own benefits, an aggregate pattern of either gathering at lattices or wave movement is distinct  Through decentralized rules, the society creates seemingly centralized activity

Sources  Axtell,R. & Epstein, J.M. Growing Artificial Societies, Brookings Institution Press, Washington, D.C,  “Introducing Sugarscape”, The Brookings Institute, 20 Jan 2006.