Emergent Cooperative Gameplay A Project Presented to the Faculty of The Guildhall at Southern Methodist University By Elizabeth England BA, Marist College, 2006 In Partial Fulfillment of the Requirements for a Masters of Interactive Technology in Digital Game Development with a Specialization in Level Design 05/05/08 Masters Thesis The Guildhall at SMU To the Graduate Faculty: I am submitting herewith a project written by Elizabeth England entitled “Emergent Cooperative Gameplay.” I recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Interactive Technology in Digital Game Development, with Specialization in Level Design. _________________________________ Michael McCoy, Supervisor/Advisor I have read this Project and recommend its acceptance: ____________________________________ Myque Ouellette, Reader Accepted for the Faculty: _________________________________ Dr. Peter Raad, Executive Director The Guildhall at SMU Elizabeth England ii 05/05/08 Masters Thesis The Guildhall at SMU ELIZABETH ENGLAND M.I.T., THE GUILDHALL AT SMU, 2008 Emergent Cooperative Gameplay Supervisor: Michael McCoy Master of Interactive Technology degree conferred May 5, 2008 Thesis / Project completed February 28, 2008 This thesis attempts to reconcile the Iterated Prisoner’s Dilemma with a game whose primary purpose is entertainment in an effort to reproduce a gradual trend from competitive gameplay to cooperative. It involves the creation of a 2D game to provide a ground to implement the Iterated Prisoner’s Dilemma and collecting data from play testers to track their choices. This game centers on a reverse-shooter game mechanic, where players either store their energy to directly increase their score or unleash their energy to create a bomb and destroy enemies on the game field, increasing their score with each kill. The players’ objective is to reach the highest score possible. Elizabeth England iii 05/05/08 Masters Thesis The Guildhall at SMU Table of Contents List of Figures .......................................................................................................................... vi List of Tables .......................................................................................................................... vii Chapter 1: Introduction ............................................................................................................. 1 Chapter 2: Field Review ........................................................................................................... 3 2:1 Cooperation in Modern Games ....................................................................................... 3 2:2 Game Theory and Cooperation ....................................................................................... 5 2:2:1 Zero-Sum Games ..................................................................................................... 5 2:2:2 Prisoner’s Dilemma ................................................................................................. 6 2:2:3 Iterated Prisoner’s Dilemma .................................................................................... 7 Chapter 3: Methodology ......................................................................................................... 10 3:1 Summary ....................................................................................................................... 10 3:2 Modified Rules of IPD .................................................................................................. 10 3:3 Implementation ............................................................................................................. 12 3:3:1 Game Overview ..................................................................................................... 12 3:3:2 Players.................................................................................................................... 12 3:3:3: Enemies ................................................................................................................ 15 3:3:4 Prisoner’s Dilemma ............................................................................................... 15 3:3:5 Technical Details ................................................................................................... 17 3:4 Data ............................................................................................................................... 22 Chapter 4: Results and Analysis ............................................................................................. 23 4:1 General Figures ............................................................................................................. 23 4:1:1 Play Tester Demographics ..................................................................................... 23 4:1:2 Cooperation and Defection Statistics..................................................................... 23 4:3 Rate of Cooperation and Defection over Time ............................................................. 27 4:4 Influence of Score on Player Strategy .......................................................................... 29 4:5 Influence of Controls on Player Strategy ...................................................................... 31 4:6 Strategy Feedback ......................................................................................................... 33 4:7 Caveats .......................................................................................................................... 35 Chapter 5: Conclusion......................................................................................................... 40 References ............................................................................................................................... 42 Books .................................................................................................................................. 42 Articles ................................................................................................................................ 42 Games ................................................................................................................................. 42 Appendix A: Session Data ...................................................................................................... 43 Pair 1 ................................................................................................................................... 43 Pair 2 ................................................................................................................................... 45 Pair 3 ................................................................................................................................... 47 Pair 4 ................................................................................................................................... 49 Pair 5 ................................................................................................................................... 52 Pair 6 ................................................................................................................................... 54 Pair 7 ................................................................................................................................... 56 Pair 8 ................................................................................................................................... 58 Pair 9 ................................................................................................................................... 60 Elizabeth England iv 05/05/08 Masters Thesis The Guildhall at SMU Pair 10 ................................................................................................................................. 62 Pair 11 ................................................................................................................................. 64 Pair 12 ................................................................................................................................. 66 Appendix B: Survey Data ....................................................................................................... 68 Pair 1 Player 1 ..................................................................................................................... 68 Pair 1 Player 2 ..................................................................................................................... 69 Pair 2 Player 1 ..................................................................................................................... 70 Pair 2 Player 2 ..................................................................................................................... 71 Pair 3 Player 1 ..................................................................................................................... 72 Pair 3 Player 2 ..................................................................................................................... 73 Pair 4 Player 1 ..................................................................................................................... 74 Pair 4 Player 2 ..................................................................................................................... 75 Pair 5 Player 1 ..................................................................................................................... 76 Pair 5 Player 2 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