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In case anyone wants a primer on the prisoner's dilemma: Suppose both you and a partner get arrested whilst trying to rob a bank. Without a confession from one

by oli5679 10y ago

In case anyone wants a primer on the prisoner's dilemma: Suppose both you and a partner get arrested whilst trying to rob a bank. Without a confession from one of you, the police can only convict you of a minor offense (say trespassing). The police place you in different cells, and offer you both the following bargain. If you confess to the robbery, and your partner does not, you get a complete pardon, and your partner gets a full sentence (say 120 months in jail). If you both confess, you get a slightly reduced 100 months in jail. Finally, if you both remain silent then each gets a 3 month sentence for trespassing. You both now have this tension between individual and collectively optimal action. Your personal sentence is smaller (independent of what your partner does) after confessing, but you both benefit from coordinating to not confess. You can draw the payoffs in a matrix (left is row player and right is column player) to visualise this. c c' c 100,100 0,120 c' 120, 0 3,3 This tension applies to lots of other interactions (e.g. firms colluding to restrict output, communities collaborating to maintain public goods, neighbours not pissing each other off by throwing massive parties). Even if there is a repeated interaction for a finite amount of time, you can expect rational self-interested agents to be unable to collaborate in the final period. This means they have no way of punishing in the penultimate round, and so by induction you would expect 'unravelling' to non-cooperation right from the beginning. This paper found that a subset of the population appearing not to be self-interested was sufficient to prevent this complete unravelling. Even a selfish player may wish to collaborate in early interactions if there is a high enough chance that they won't be immediately punished. https://en.wikipedia.org/wiki/Prisoner's_dilemma https://en.wikipedia.org/wiki/Prisoner's_dilemma

thilmo 10y ago
When I was a kid and I read about the Prisoner's dilemma in the context of morality, I was always confused. Surely the moral thing is to confess if you're guilty. If you're guilty, and your accomplice is guilty, the right thing to do is confess to the police so that you can be rightfully punished. As an adult I understand that this isn't the point of the story, and the police-and-prisoners aspect of the story is completely extraneous to the point trying to be made. Still, I can't help but think that the police-and-prisoners is a bad example of the broader point, since there's always a third set of interests (that of the police, and of society in general) which is callously (and immorally) tossed aside in the phrasing of the problem.
- Nomentatus 10y ago
  But the problem has to explicitly exclude altruistic behavior; since if both subjects view the consequences to the other subject as being roughly as serious as consequences to themselves, there's no dilemma at all. They both shut up and help each other. The whole point is to show a situation exists in which two purely rational, purely selfish actors get an outcome that's actually worse for them from a selfish point of view than the outcome that two altruistic or irrational players would get. That they are criminals "establishes", to use the story-telling term, that these subjects are (unusually) not altruistic at all - the punchline is that being self-serving turns out not so well for them.

by oli5679 10y ago

thilmo 10y ago

When I was a kid and I read about the Prisoner's dilemma in the context of morality, I was always confused. Surely the moral thing is to confess if you're guilty. If you're guilty, and your accomplice is guilty, the right thing to do is confess to the police so that you can be rightfully punished. As an adult I understand that this isn't the point of the story, and the police-and-prisoners aspect of the story is completely extraneous to the point trying to be made. Still, I can't help but think that the police-and-prisoners is a bad example of the broader point, since there's always a third set of interests (that of the police, and of society in general) which is callously (and immorally) tossed aside in the phrasing of the problem.

Nomentatus 10y ago
But the problem has to explicitly exclude altruistic behavior; since if both subjects view the consequences to the other subject as being roughly as serious as consequences to themselves, there's no dilemma at all. They both shut up and help each other. The whole point is to show a situation exists in which two purely rational, purely selfish actors get an outcome that's actually worse for them from a selfish point of view than the outcome that two altruistic or irrational players would get. That they are criminals "establishes", to use the story-telling term, that these subjects are (unusually) not altruistic at all - the punchline is that being self-serving turns out not so well for them.