Coye Cheshire & Andrew Fiore March 21, 2012 // Computer-Mediated Communication Collective Action...

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