Prisoner's Dilemma
Cooperation pays when you will meet again, nobody knows which round is the last, and the other side answers in kind.
5 minutes · trains Cooperate or defend · points only, never money
Each round, you and a bot each choose to cooperate or defect, at the same time. Defecting on a cooperator scores best for you in that round, but the game goes on, and the bot remembers. Play one bot, or all five in turn, and see how many points you can make.
Choose a bot
Each match lasts about ten rounds. You will not know which round is the last.
- Cooperates every round, whatever you do.
- Defects every round, whatever you do.
- Cooperates first, then copies your last move.
- Like tit for tat, but forgives a defection 1 time in 3.
- Cooperates or defects at random, half and half.
Try it yourself
Two teams share a budget that is split again every quarter, with no end date. Each could grab more this quarter. What best keeps both from grabbing?
3 questions, a minute or two. Nothing to finish first.
Want more? Practise Cooperate or defend.
Read more
- Prisoner's Dilemma Two players each do better by betraying, yet both do better together if both cooperate.
- Tit for tat Cooperate first, then copy what the other player did last time.
- Cooperate or defend When you will meet again, cooperation and reputation pay. In a one-off, protect yourself in the terms, but remember that few deals are truly one-off.
- Nash equilibrium A set of choices where no player can do better by changing only their own.
- The Cooperate or defend course Lessons and practice for the skill this lab trains.