1 / 20

Game Theory

Game Theory. by James Crissey Luis Mendez James Reid. Complex Adaptive Systems and the Evolution of Reciprocation. by Karl Sigmund University of Vienna. Human Societies. cooperation is ubiquitous few individual inequalities in reproductive potential

sunee
Télécharger la présentation

Game Theory

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Game Theory by James Crissey Luis Mendez James Reid

  2. Complex Adaptive Systems and the Evolution of Reciprocation by Karl Sigmund University of Vienna

  3. Human Societies • cooperation is ubiquitous • few individual inequalities in reproductive potential • social rules level reproductive opportunities and prevent establishment of global controller

  4. Human cooperation • not based on relatedness • Based on reciprocation • based on economic exchanges • human cohesiveness is explained based on economic exchanges

  5. Game theory • studies the economics of interacting egoists - non-cooperative game theory • players cooperate, not by the command of a controller or by deference to the group • cooperation based on rules

  6. Game theory cont . . . • Trivers • suggested reciprocation as mutual assistance • introduced the prisoner’s dilemma

  7. Expansion of Trivers Findings • 1981 Axelrod and Hamilton applied the evolutionary game theory to players engaged in many rounds of the prisoners dilemma game against randomly chosen co-players. • Axelrod adapted the genetic algorithms of John Holland to simulate the effects of evolutionary trial and error.

  8. Expansion of Trivers finding cont. • First application of genetic algorithms to a genuine evolutionary problem rather than a technical optimization problem

  9. Indirect reciprocity • Alexander (1987) the biological basis for human moral systems • an act of assistance may be returned not to the donor but a third party

  10. Direct Reciprocation • Prisoner’s dilemma is a two-player game where both players have the same two strategies and the same payoff

  11. Direct Reciprocation • Prisoner’s dilemma • two-player game in which both player’s have the same two strategies as well as the same two payoffs • can to cooperate or defect • rewarded based on what they choose

  12. Direct Reciprocation cont . . . • PD game player’s choose simultaneously whether they want to cooperate or defect • assumes that if player starts off by cooperating and then does what ever the other person does

  13. Direct Reciprocation cont . . . • Generous Tit for Tat (GTFT) • person retaliates sometimes after players defects • but always cooperates after they cooperate • Pavlov rule, suggests that people will cooperate if they use the same rule in the first round- assumes that players will repeat a move if it leads to high payoff

  14. Indirect Reciprocation • the donor does not obtain a return from the recipient • donor receives return from third party • cost of an altruistic act is offset by a raised ‘score’ or status, which increases chance to subsequently become the recipient of an altruistic act

  15. Indirect Reciprocation cont . . . • Indirect reciprocity involves reputation and status, and results in everyone in the group continually being assessed and re-assessed (Alexander, 1987) • Nowak and Sigmund (1998) • model of indirect reciprocation

  16. Indirect Reciprocation cont... • in donor who provides there is a cost • however, the donor’s score increases • if player refuses to play, score decreases • if the frequency of less discriminating reaches a certain threshold, then defectors can take over, with the result that cooperation disappears in the population

  17. Indirect discrimination cont . . . • random drift can subvert populations of discriminate altruist by indiscriminate altruist • once there frequency is too large, defectors can invade; but as soon as defectors reduce the proportion of indiscriminate altruist, the discriminate altruists fight back and eliminate the defectors

  18. Indirect Reciprocation • this leads to a cooperative population which is proof against defectors, but not against indiscriminate altruists • chances of two players meeting again is low • must know the score of the co-player • interaction between two individuals is only observed by a small subset of the population

  19. Indirect reciprocation cont . . . • only the few on-lookers will update score of donor • For larger groups it is difficult to establish cooperation • for indirect reciprocation to function • compute minimal amount of discriminators • minimal amounts of rounds per generation • maximal size of society

  20. Discussion/Critical Analysis • underestimates kinship and genetic relatedness

More Related