Analysis of complex social systems by agent-based simulation

Abstract

This dissertation studied complex social systems that have large number of individuals and complicated functional relations among individuals. Prisoner's Dilemma (PD) including Social Dilemmas (SDs) is a type of problem arising from collective actions in social systems. Previous PD studies have limitations and are not suitable for the study of collective actions in complex social systems. The large number of individuals and the complexity of the models made the development of theoretical, analytical studies impossible. An agent-based computer simulation is used in this dissertation for investigating N-person Prisoner's Dilemma (NPD), and its new extensions. My research can be divided into three chapters (three appendixes in this dissertation). In the first problem, the classical NPD model is considered, a much faster algorithm was developed, and the long term behavior of Pavlovian agents is examined. In this study, the main feature of the classical PD model was kept by restricting the state space into two possibilities: cooperation and defection. In most social situations the state space is much more complicated. In the second study, NPD was introduced with continuous state space. A continuous variable described the cooperation level of the participating individuals. A stochastic differential equation models state change of individuals. Public media and personal influence were first introduced in the study of NPD. In the third model, we analyzed the dynamic process of fund raising for a public radio station. This model is a combination of the other two models; discrete in the sense that donating or not in a time period is discrete variable; however the amount the individuals can pledge to the station is a continuous variable. In all three models, individual personalities are considered and quantified. Major personality types that might affect the possible cooperation or defection of the agents were captured in the continuous NPD simulation; major motivations that might affect the probability of pledging at a certain time period and the pledged amount were captured in the fund raising case. During the computer simulation, the behavior of each agent and the behavior of the entire society can be monitored.