The Prisoner's Dilemma

Why rational self-interest leads to collective disaster — and what makes cooperation possible

Payoff Parameters

Mutual Cooperation (R)3

Temptation to Defect (T)5

Sucker's Payoff (S)0

Mutual Defection (P)1

✓ Valid PD: T > R > P > S

PD requires: T > R > P > S
Iterated PD also: 2R > T + S
(cooperation must beat alternating)

Opponent Strategy

Tit-for-Tat: Cooperates first, then mirrors your last move. Nice, retaliatory, forgiving, clear.

Shadow of the Future

Discount factor (δ)0.90

                Cooperation is sustainable in a repeated PD when δ ≥ (T−R)/(T−P). Currently δ* = 0.50. Your δ = 0.90 — cooperation can be sustained.
            

Play the Game

Your Total

Your Avg

—

Round

Opp Avg

—

Opp Total

	Opp: Cooperate	Opp: Defect
You: Cooperate	3, 3	0, 5
You: Defect	5, 0	1, 1

■ Nash Eq (D,D) ★ Pareto Optimal (C,C) ◆ Last outcome

🤝 Cooperate Risk the sucker's payoff for mutual gain

🗡️ Defect Dominant strategy in a one-shot game

Round History

Both C

You C, Opp D

You D, Opp C

Both D

                In a one-shot PD, Defect is the dominant strategy — it's better regardless of what the opponent does.
                But in a repeated game, the shadow of the future can sustain cooperation. Choose your move!
            

Cumulative Score & Cooperation Rate

Your Cum. Score

Opponent Cum. Score

Cooperation Rate Over Time

Your Coop %

Opp Coop %

Mutual Coop %

One-Shot Payoff Landscape — Why Defection Dominates

Your payoff if you Cooperate

Your payoff if you Defect

Temptation gap