The "grim trigger" strategy is an angle in

game theory, particularly pertaining to infinite

iteration and the

prisoner's dilemma. The idea is to create a

Nash Equilibrium (NE) of the

Pareto Optimal solution through repeating games where there was previously a non-Pareto optimal

dominant strategy.

...a little payoff matrix to refresh you

`
2,2 0,7`

7,0 1,1

The strategy basically goes like this: "Do not confess (

cooperate with me) and we will continue a cooperative tradition to

perpetuity. The payoff for this is 1+1*delta+1*delta^2+...1*delta^n where delta is your discount rate for future payoffs. (remember the lowest score is best in prisoner's dilemma) If you ever confess (cross me) then I will forever punish you by confessing. Period. No forgiveness possible. Assuming you find this to be a

credible threat (a fair assumption unless you have some other information about my personal

discount rate) it is an NE for you to cooperate.