Monday, August 8, 2011

The Prisoners Dilema


  Two criminals are arrested for a robbery, and the police do not have enough evidence to convict them. They separate the two suspects and make them the same offer. if they both confess, they will both serve two years. If one of them confesses , but the other one stays silent, the confessor will go free and the silent partner will serve ten years in prison. However, if neither one of them says a word, if they trust each other, -they will both serve only six months. Neither one knows what the other one is going to do. Is it better o hold your tongue or to squeal? This hypothetical situation is known as the Prisoners Dilemma first proposed by mathematician Albert W. Tucker. It has an important implications for game, theory, economics, evolution, and psychology. 
  
   The prisoners Dilemma          Prisoner B Remains Silent               Prisoner B Confesses
   

  Prisoner A Remains Silent        They both serve 6 months                    Prisoner B walks free
                                                                                                 Prisoner A serves ten years 

  Prisoner A confesses                 Prisoner A walks free                  They both serve two years
                                                Prisoner B serves two years.      


The rational choice for prisoner A seems to be betray his partner and confess. The outcomes are better. but Prisoner A knows that prisoner B will probably think the same way. They will both wind up serving two years. Of course, if they could only trust each other, they would only serve six months.

In 1980, scientist Robert Axerlrod performed an experiment called the iterated prisoner's dilemma. Essentially, participants played the prisoners dilemma over and over again, sometimes with the same partners and sometimes with different partners. Players were allowed to use information from past encounters. Some people developed greedy strategies tending toward betrayal some players developed altruistic strategies tending toward trust. over long periods of time, the altruistic players fared better than the greedy players. This tells us that nice guys do finish first.

** Two countries in an arms race are often thought to be playing out Prisoner's Dilemma. They can both spend a lot of time and money increasing their arsenal in order to keep pace with each other, or they can agree to disarm. But how can they know for certain if the other country isn't still bulking up in secret.

** Males in the animal kingdom often exhibits behavior that fits the pattern of the prisoner's dilemma. Do you you just strut your stuff, back down, or engage in the cockfight? The best strategies in the animal kingdom seem to encompass a little of each approach.




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