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Rules
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Build Lineup
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Run Tournament
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Match Highlights
Axelrod's Iterative Prisoner's Dilemma
Can cooperation evolve among purely self-interested agents?

🔒 The Prisoner's Dilemma

  • Two players each choose, simultaneously and secretly, to Cooperate or Defect.
  • Mutual cooperation yields a moderate reward for both. Mutual defection yields a low payoff for both.
  • If one defects while the other cooperates, the defector gets the highest payoff and the cooperator gets nothing.
  • Defecting is always individually rational in a single round — yet mutual defection is worse than mutual cooperation.

🔁 Iterative Prisoner's Dilemma & This Simulator

  • When repeated over many rounds, players can build reputations, reward cooperators and punish defectors.
  • In 1980, Robert Axelrod ran a landmark round-robin IPD tournament with 15 submitted strategies.
  • He found that Nice, Forgiving and Clear strategies consistently outperformed aggressive ones.
  • This simulator recreates that tournament.
Payoff Points for This Simulator
🤝 Cooperate × Cooperate
+3 / +3 pts
Mutual trust
😇 Cooperate × Defect
+0 / +5 pts
Sucker's payoff
😈 Defect × Cooperate
+5 / +0 pts
Temptation
💀 Defect × Defect
+1 / +1 pts
Mutual punishment
Select 10 of the 17 strategies, set the number of rounds, and see who dominates.
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Rules
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Build Lineup
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Run Tournament
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Match Highlights
Stage 1: Understanding Strategies in Prisoner's Dilemma
Nice Nasty
Selected: 0 / 10
Strategy Definition
Click a strategy to see its definition
Live Preview — Head to Head
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Rounds:
Strategy A Score
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Strategy B Score
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Select two strategies and click Live Preview
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Rules
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Build Lineup
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Run Tournament
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Match Highlights
Stage 2: Tournament Mode — Iterative Prisoner's Dilemma
Rounds
Leaderboard — Round by Round
Round 0 / 0
Pos. Prev. Strategy Tournament Points Pts #Wins
Run Tournament to start
Rank Race — Position Over Rounds
Click an icon to highlight a strategy
Tournament Results
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Rules
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Build Lineup
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Run Tournament
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Match Highlights
Match Results
Run Tournament first
Click "▶ Highlight" on any match to replay it round by round
Match
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B
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Strategies
Click ▶ Highlight to see definitions
Iterative Prisoner's Dilemma
A recreation of Robert Axelrod's landmark 1980 IPD tournament. Select strategies, set rounds, and discover whether cooperation or defection dominates.
  • 10 of 15 original Axelrod strategies — Tit-for-Tat, Grudger, Random and more
  • Round-robin tournament with live points race & match-by-match replay
  • Payoffs: C×C = 3/3 · C×D = 0/5 · D×D = 1/1
  • Analyses Nice vs Nasty strategy groups and infers key insights