Saturday, July 21, 2012

Prisoner's Dilemma

By Julie Rahm                      
           Surprising to some, my educational background is in physics. And, in order to do the mind-blowing math required for a physics degree, a degree in math was also required. My math studies gave me a broad understanding of statistics and game theory.  The corner stone of game theory is a simple concept or game called prisoner’s dilemma.
           In prisoner’s dilemma, two men are arrested with not enough evidence to convict either. The two are separated. The police offer each prisoner the same deal. If one testifies against the other, and the other remains silent, the betrayer goes free and the silent prisoner gets the full one-year sentence. If both remain silent, both are sentenced to one month. However, if each betrays the other, both receive a six-month sentence. What should the prisoners do?
           The dilemma becomes a game where the two may either betray or assist each other. In the game, the sole worry of the prisoners seems to be increasing their own reward. If one prisoner testifies and the other doesn’t, the testifying prisoner goes free. The interesting symmetry of this problem is that the rational decision leads each to betray the other. Yet, the outcome obtained when both testify against one another is worse for each than the outcome they would have obtained had both remained silent.
The common view is that the dilemma illustrates a conflict between individual and group interests. A group whose members pursue rational self-interest may all end up worse off than a group whose members act contrary to rational self-interest.
A slightly different interpretation takes the game to represent a choice between selfish behavior and socially desirable altruism. The move corresponding to testifying benefits the prisoner, no matter what the other does, while the move corresponding to silence benefits the other prisoner no matter what that prisoner does. Benefiting oneself is not always wrong. Benefiting others at the expense of oneself is not always morally required. The paradox in the prisoner's dilemma game is that the altruistic cooperative outcome is better for everyone involved. Most game theory experts use prisoner's dilemma to reveal the nature of morality. Once you recognize it, examples of the prisoner’s dilemma are evident everywhere.
The Fulcher/Town of Oriental waterfront land swap is a classic case of game theory and the prisoner’s dilemma. Is Mr. Fulcher the betrayer increasing his own reward at the expense of the Town? Or is town of Oriental the betrayer to the detriment of Mr. Fulcher? When both the Town and Mr. Fulcher make altruistic choices and avoid self interest, the outcome will be better for both. Achieving cooperation in the prisoner’s dilemma proves to be a difficult and relevant problem.
Prisoner’s dilemma situations arise frequently in life. You have likely played the game. In some cases, you found a way to cooperate. In other cases, one of you betrayed the other. Think of examples from your own life and ask yourself: What made the difference? Then, comment on my blog at

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