The Mathematics of Tit for Tat

+VincentKnight
@drvinceknight
vknight.org

vknight.org/Talks/

Themes

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Golden Balls

TV show from Feb 2008 to Feb 2009 where a jackpot is to be shared between 2 contestants who secretly choose to "split" or "steal".

  1. If both players "split", the jackpot is split equally between them.
  2. If 1 player "splits" and the other "steals", the stealer gets the whole jackpot and the splitter leaves with nothing.
  3. If both players "steal", they both leave with nothing.
Cooperate Defect
Cooperate (3,3) (0,5)
Defect (5,0) (1,1)

Axelrod's computer tournament

3 teams

Cooperator

Always cooperate.

Defector

Always defect.

Alternator

Start by cooperating and then switch.

Random

Play randomly.

Tit For Tat

Start by cooperating and then do whatever your opponent does in the previous round.

1 2 3 4 5 6 7 8
Alternator C D C D C D C D
Tit For Tat C C D C D C D C


C D
C (3,3) (0,5)
D (5,0) (1,1)


1 2 3 4 5 6 7 8
Alternator 3 5 0 5 0 5 0 5
Tit For Tat 3 0 5 0 5 0 5 0

Alternator Cooperator Defector Random Tit For Tat
Alternator 2.0 4.0 0.5 2.3 2.5
Cooperator 1.5 3.0 0.0 1.5 3.0
Defector 3.0 5.0 1.0 3.0 1.0
Random 2.2 4.0 0.5 2.3 2.7
Tit For Tat 2.5 3.0 1.0 2.3 3.0
A lot of strategies...
Year Author Size Source Code
1979 Axelrod 13 Not immediately available
1979 Axelrod 64 Not immediately available
1979 Axelrod 64 Available
1991 Bendor 13 Not immediately available
2002 Stephens 16 Not applicable
2005 Kendall 223 Not available
2012 Stewart 13 Not fully available
github.com/Axelrod-Python/Axelrod

Demonstration

Applications of Game Theory

  • Economics
  • Biology
  • Computer Science

(1928-2015)

Brouwer's fixed point theorem

@drvinceknight
vknight.org

http://axelrod.readthedocs.org/en/latest/