1. Coye Cheshire & Andrew Fiore March 21, 2012 // Computer-Mediated Communication Collective Action and CMC: Game Theory Approaches and Applications

2. 5/6/2015Computer-Mediated Communication1 Why Game Theory for mediated communication?

3. 5/6/2015Computer-Mediated Communication2 Game Theory (definition) “Game theory is the systematic study of interdependent rational choice. It may be used to explain, to predict, and to evaluate human behavior in contexts where the outcome of action depends on what several agents choose to do and where their choices depend on what others choose to do.” http://plato.stanford.edu/entries/game-ethics/

4. 5/6/2015Computer-Mediated Communication3 Game Theory and Core Concepts  Analytical vs. Behavioral Game Theory  Cooperative and Non- Cooperative Games  Zero and Non-Zero Sum Games  One-Shot vs. Repeated  Equilibria  (i.e., Nash Equilibrium) (example for cooperative game)

5. 5/6/2015Computer-Mediated Communication4 Types of Social Dilemmas Different social dilemma games make different use of the payouts: T>R>P>S Prisoner’s Dilemma But also… T>R>S>P Chicken T>P>R>S Deadlock R>T>P>S Stag Hunt Coop.Defect Coop. Defect A B 3 (R) 5 (T) 0 (S) 3 (R) 0 (S) 5 (T) 1 (P) Reward Temptation Sucker Punishment

6. 5/6/2015Computer-Mediated Communication5 Example: Chicken Game T>R>S>P Chicken Coop = Swerve Defect = Do Not Swerve SwerveNo Swerve Swerve No Swerve A B 3 (R) 5 (T) 1 (S) 3 (R) 1 (S) 5 (T) -1 (P) Reward Temptation Sucker Punishment

7. 5/6/2015Computer-Mediated Communication6  2-person repeated PD  N-person PD Public Good

8. The N-person PD 5/6/2015Computer-Mediated Communication7 “No one wants to pay taxes because the benefits are so diffuse and the costs are so direct. But everyone may be better off if each person has to pay so that each can share the benefits” cf. Schelling 1973; Axelrod 1984 http://www.flickr.com/photos/cogdog/4353774/

9. In-Class Tournaments 5/6/2015Computer-Mediated Communication8

10. Small Group Discussion #1  Get into a small group (2-3 students, three groups total)  Imagine you are going to play in a series of separate tournaments, each against a single strategy for exactly 10 rounds. Your goal is to make the most points.  What strategy would you use if you were going to play against All- Cooperate?  What strategy would you use if you play against All-Defect?  What strategy would you use if you play against Random (i.e., cooperation and defection are always randomly chosen)? 5/6/2015Computer-Mediated Communication9

11. 5/6/2015Computer-Mediated Communication10 The Evolution of Cooperation  Axelrod’s famous (1984) tournament allowed individuals to submit any strategy.  All strategies played each other in the tournament.  The winner was one of the shortest submissions, about 4 lines of code.

12. 5/6/2015Computer-Mediated Communication11 The Simple Effectiveness of the Tit-for-Tat Strategy  Tit-for-Tat: begin with ‘cooperate’ and then do whatever the opponent did on the last turn.

13. 5/6/2015Computer-Mediated Communication12 Lessons from Tit-for-Tat  Be nice  It starts by cooperating. Most top- scoring strategies do this.  Be forgiving  It quickly and happily returns to cooperation without holding a grudge.  Be able to retaliate  It never allows defection to go unpunished.  Be clear  It is predictable and easy to understand. It pays to be predictable in non-zero sum games.

14. Considering the “Shadow of the Future” 5/6/2015Computer-Mediated Communication13

15. How is tit-for-tat different in the two types of situations? 5/6/2015Computer-Mediated Communication14  2-person repeated PD  N-person PD Public Good

16. 5/6/2015Computer-Mediated Communication15 Some common complaints…  “A theoretical tool cannot explain real life, right?”  “Hey, isnt this rational choice?” (Picture courtesy vismod.media.mit.edu)

17. 5/6/2015Computer-Mediated Communication16 The Value Fallacy: Individuals and Collectives