Editing Prisoner's dilemma (section)

==Strategy for the prisoner's dilemma==
{{More citations needed section|date=January 2023}}
Two prisoners are separated into individual rooms and cannot communicate with each other. It is assumed that both prisoners understand the nature of the game, have no loyalty to each other, and will have no opportunity for retribution or reward outside of the game. The normal game is shown below:{{sfn|Poundstone|1993|p=118}}

{| class="wikitable"
|-
! {{diagonal split header|<br />Prisoner A|Prisoner B}} !! Prisoner B stays silent<br />(''cooperates'') !! Prisoner B testifies<br />(''defects'')
|-
! Prisoner A stays silent<br>(''cooperates'')
| Each serves 1 year|| Prisoner A: 3 years<br />Prisoner B: goes free
|-
! Prisoner A testifies<br />(''defects'')
| Prisoner A: goes free<br />Prisoner B: 3 years || Each serves 2 years
|}

Regardless of what the other decides, each prisoner gets a higher reward by betraying the other ("defecting"). The reasoning involves analyzing both players' [[best response]]s: B will either cooperate or defect. If B cooperates, A should defect, because going free is better than serving 1 year. If B defects, A should also defect, because serving 2 years is better than serving 3. So, either way, A should defect since defecting is A's best response regardless of B's strategy. Parallel reasoning will show that B should defect.
<!-- an argument by [[Dilemma#Use in logic|dilemma]] -->

Defection always results in a better payoff than cooperation, so it is a strictly dominant strategy for both players. Mutual defection is the only strong [[Nash equilibrium]] in the game. Since the collectively ideal result of mutual cooperation is irrational from a self-interested standpoint, this Nash equilibrium is not [[Pareto efficient]].