prisoners' dilemma

prisoners' dilemma
The classic problem in game theory . Two prisoners jointly charged with a crime are held apart, and each is given the option of confessing, or not confessing. If neither confesses, the prosecutor will find a lesser charge, and each will serve two years. If each confesses, he convicts them both, and they will serve six years each. If A confesses and B does not, A is released and B serves an aggravated ten years. If B confesses and A does not, B is released, and A serves an aggravated ten years. The matrix is shown in the figure:
The surprising truth about the game is that whatever the other prisoner does a prisoner does better by confessing (if A confesses, B does better for himself by confessing, and if A does not confess, B does better for himself by confessing; and conversely for A if B confesses or does not confess). Confessing dominates not confessing. Yet the social result in which each of A and B follows this reasoning is the worst of all (12 person-prison years) and together they would have done much better by sitting tight (4 person-prison years). Many political situations (e.g. whether to vote when there is a cost to doing so, whether to refrain from wage-bargaining, whether to be a good citizen and turn off one's hose during a water shortage) can be modelled as prisoners' dilemmas. The structure shows that it is not always the case that the social good is furthered efficiently by each person doing what is in his or her own best interests: as well as an ‘invisible hand’ whereby unbridled self-interest elevates everybody's position, there can be an invisible boot whereby it diminishes it (see Smith, Adam).
An iterated prisoners' dilemma is a sequence of such situations, of either finite or infinite length. In an interesting study (The Evolution of Cooperation, 1984) Robert Axelrod showed that an efficient policy in such a situation is ‘tit for tat’: you start off co-operating (not confessing) until faced with a play on which the opponent ‘rats’, and then you rat (confess) once in retaliation, but then, if the opponent mends his ways, you go back to not confessing until the same thing happens again. As well as being an efficient strategy ‘tit for tat’ has some intuitive moral justification. However, the strategy is sensitive to the ratio of rewards and penalties that are in play, and cannot be said to be the single best strategy for all circumstances.

Philosophy dictionary. . 2011.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • prisoners' dilemmas — prisoners dilemma …   Philosophy dictionary

  • dilemma — The simplest form of a dilemma is an argument of the form: ‘If p then q, if not p then q, so in any event q .’ More complex forms were traditionally distinguished. A constructive dilemma is of the form: ‘If p then r, if q then r, but either p or… …   Philosophy dictionary

  • Prisoner's dilemma — This article is about game theory. For the 1988 novel, see Prisoner s Dilemma (novel). For the Doctor Who audiobook, see The Prisoner s Dilemma. For the 2001 play, see The Prisoner s Dilemma (play). The prisoner’s dilemma is a canonical example… …   Wikipedia

  • The Prisoner's Dilemma — Bigfinishbox title=The Prisoner s Dilemma series= Doctor Who number= featuring=Ace writer=Simon Guerrier director=Lisa Bowerman producer= executive producer= production code=BFPDWCC15 set between=TBC length= date=January 2009| The Prisoner s… …   Wikipedia

  • Social dilemma — Social dilemmas are situations in which private interests are at odds with collective interests. Such situations arise because people frequently attach more weight to their short term selfish interests than to the long term interests of the group …   Wikipedia

  • Prisoner's Dilemma — A paradigmatic instance in game theory , which takes its name from a story of two prisoners, who are interrogated separately and cannot communicate with each other. There is insufficient evidence for the police to convict either prisoner of armed …   Dictionary of sociology

  • prisoner’s dilemma — A branch of *game theory that systematically analyzes strategies for the optimal selection of alternative courses of action in competitive conditions. The prisoner’s dilemma focuses on the complexities of making competitive choices. In a… …   Auditor's dictionary

  • prisoner's dilemma — n. in game theory, a situation in which, if each of the individuals involved chooses the most rational option for gaining his or her own ends, the least desirable outcome for all will necessarily result * * * Imaginary situation employed in game… …   Universalium

  • prisoner's dilemma — noun (in game theory) a situation in which two players each have two options whose outcome depends crucially on the other s simultaneous choice, exemplified by two prisoners separately deciding whether to confess to a crime …   English new terms dictionary

  • ДИЛЕММА ЗАКЛЮЧЕННЫХ — (prisoners dilemma) парадигматический случай в теории игр, когда каждому из двух заключенных, против которых имеются доказательства преступления, не достаточные для обвинения, и которые не могут общаться друг с другом, обещают облегчить наказание …   Большой толковый социологический словарь

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”