Monday, March 22, 2010

The Prisoners' Dilemma and Google Search

I'm about a third of the way through A Beautiful Math.  I just read about the Prisoners' Dilemma, which I've certainly heard about before but never really understood.  Here's the setup:

Two people are arrested for bank robbery, and interrogated by the police separately.  If they both rat on each other, they get 3 years each.  If one of them rats on the other and the other says nothing, the rat goes free and the quiet one gets 5 years.  If both of them keep their mouths shut, they each get 1 year.

My first thought is that they both have to both keep their mouths shut; it seems like the best thing to do.  But A Beautiful Math (which, for the record, is kind of a stupid name) is making a point about equilibrium.  Each of them keeping their mouths shut is not a stable situation.  Maybe they'll each do it this time, and next time, but at some point one of them is going to want to rat on the other, and that guy could end up doing 5 years.  The stable decision (and therefore the best one) is to always rat on your partner, because regardless of what your partner does, your situation is optimized.  

Let's look at it from one prisoner's perspective.  Say Person A rats Person B out.  If B also rats A out, A gets 3 years, and if B doesn't rat A out, A goes free.  However, if A stays quiet, he's taking a risk that B could rat him out and get him 5 years.  Maybe B will stay quiet and things will work out for A, but maybe it won't.  Ratting your partner out is the stable, sustainable solution.

My second point today: looking at my google search history is somewhat amusing.  I think I will share it from time to time.  Here's my current one:

  • What are some common verbs?
  • Translate spoorloos
  • Dutch conjugate bark
  • words that rhyme with liz
  • mad rollin dolls [the local roller derby league]
  • is fred schneider gay? [he is.]

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