The Prisoner's Dilemma
Two individuals are arrested and imprisoned in different and isolated cells. The prosecutor suspects that they have participated in a bank robbery. The crime is punished with 10 years in jail, but he cannot prove it. The only evidence is related to illegal possession of weapons, a crime which is punished with 2 years in jail. In order to get incriminatory information from the prisoners, the prosecutor promises to each one of them to reduce their final sentence to half if they provide the proofs that will inculpate the other prisoner.
Given those conditions, what is the best decision that a prisoner can take?
Possible outcomes
Let's have a look into this problem. First of all, and in sake of simplicity, I will name the prisoners as A and B. We can find that there are only four possible outcomes in this story:
1) Prisoner A remains silent and prisoner B as well --> Both of them get a 2 years sentence for illegal possesion of weapons.
2) Prisoner A remains silent, but prisoner B betrays A --> Prisoner A gets a 10 years sentence and prisoner B gets a 2 year sentence that is then reduced by half in regard of his cooperation, so he stays only 1 year in jail.
3) Prisoner A betrays B and prisoner B remains silent --> Prisoner A stays 1 year in jail and B stays 10 years.
4) Prisoner A betrays B and prisoner B betrays A --> Both of them get in principle a 10 year sentence, but the sentences are reduced to 5 years because of their cooperation.
The story seems to be just an entertaining riddle. But it happened to be the starting point in a very interesting quest to explain certain components of human morality such as altruism, solidarity, trustfulness and forgiveness.I will stop here by now. But in future posts I will keep commenting on this issue.
