ITERATED PRISONER'S DILEMMA SIMULATOR

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Information & Instructions

Background

The Prisoner's Dilemma is a classic problem in game theory. Two prisoners (players) are interrogated separately and must each decide, without communication, whether to cooperate (stay silent) or defect (betray the other). The iterated version plays this game over many rounds, allowing strategies based on past decisions to emerge.

Robert Axelrod's famous 1980 computer tournament invited Game Theorists to submit strategies to compete against each other. The best performing strategy was the deceptively simple Tit for Tat, written in just 4 lines of BASIC: cooperate on the first round, then mirror the opponent's last move (retaliate when and only when the opponent defects).

Payoff Structure

The following conditions are required for a valid Iterated Prisoner's Dilemma:

• T > R > P > S (Single Round Condition)
• 2R > T + S (Iterative Condition)

Outcome	Symbol	Points	Condition
Temptation	T	5	You defect, opponent cooperates
Reward	R	3	Both cooperate
Punishment	P	1	Both defect
Sucker	S	0	You cooperate, opponent defects

How to Use

• Select the number of rounds (1-10,000) and choose a strategy for each player.
• Pick from the list of provided algorithms or select Custom Algorithm to write your own JavaScript.
• Click ▶ Run Simulation. Results of the simulation should appear if both algorithms are runnable.

Writing a Custom Algorithm

Your code runs as a JavaScript function body with these variables as input parameters:

• myMoves — array of your past moves (true=cooperate, false=defect)
• opponentMoves — array of opponent's past moves
• round — current round index, 0-based. Size of each array is equal to the current round.

Return true to cooperate or false to defect. See the provided algorithms for examples. Note that returning anything other than true will internally default to returning false.