coye cheshire & andrew fiore march 21, 2012 // computer-mediated communication collective action...
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Coye Cheshire & Andrew Fiore March 21, 2012//
Computer-Mediated Communication
Collective Action and CMC: Game Theory Approaches and Applications
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Why Game Theory for mediated communication?
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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/
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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)
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Types of Social DilemmasDifferent social dilemma gamesmake 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)1 (P)
Reward
Temptation
Sucker
Punishment
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Example: Chicken GameT>R>S>P Chicken
Coop = Swerve
Defect = Do Not Swerve
Swerve No Swerve
Swerve
No Swerve
A
B
3 (R)
5 (T)
1 (S)3 (R)
1 (S)
5 (T)
-1 (P)-1 (P)
Reward
Temptation
Sucker
Punishment
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2-person repeated PD N-person PD
Public Good
The N-person PD
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“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/
In-Class Tournaments
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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)?
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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.
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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.
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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.
Considering the “Shadow of the Future”
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How is tit-for-tat different in the two types of situations?
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2-person repeated PD N-person PD
Public Good
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Some common complaints…
“A theoretical tool cannot explain real life, right?”
“Hey, isnt this rational choice?” (Picture courtesy vismod.media.mit.edu)
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The Value Fallacy: Individuals and Collectives