"Prisoner Dilemma" is one of the most classic examples in game theory. It is said that two suspects (A and B) have been caught by the police after committing crimes; the police's policy is "frankly from wide, resistant strictness", if the two are frank, each sentence; One person does not frank, frankly, and did not frankly sentenced to 10 years; if it did not frank, it was sentenced to 1 year due to evidence. In this example, the participants of the game are two suspects A and B. Each of them has two strategies, that is, frank and unfold, and the number of sentences is their payment. Four cases that may occur: A and B are dominant or unspeakable, and A is not confession or B frank A is not confession, which is the result of the game. A and B are all frankly the Nash equilibrium of this game. This is because it is assumed that the B is better to choose, because B is more than 8 years, but it is necessary to sentence ten years; if a choice is redeemed, B is best to choose confession, because B is not called The sentence is sentenced to 1 year in prison. That is to say, regardless of the confession or represented, the best choice of B is frank. In turn, the same, regardless of whether B is frank or represented, the best choice of A is also frank. As a result, both of them have chosen frankness, each sentence of 8 years. In (frank, confession) this combination, both A and B can increase their own benefits through unilateral changes, so no one has no power free of which this combination is Nash. The prisoner's dilemma reflects the contradiction between personal rationality and collective rationality. If A and B choose to reply, each sentence is 1 year, it is obviously more than 8 years to choose more than 8 years. Of course, A and B can set a "attack and defensive alliance" before being caught by the police, but this may not be useful, because it does not constitute Nash balance, no one has enthusiasm to comply with this agreement.
