Reciprocal Altruism

Sucker, Cheater, Grudger

Repeated prisoner's dilemma dynamics from chapter 10 of The Selfish Gene.

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System State

Current Population

Population strip

Strategy share

Current generation

Average payoff

Last generation

History

Population Trajectory

Sucker Cheater Grudger Cooperation

Controls

Population Setup

Population mix, match structure, and mutation apply on reset. Playback speed updates immediately.

Reading The Model

What This Simulation Is Doing

Sucker

Always cooperates. It does best when surrounded by other cooperators and worst when exposed to persistent cheaters.

Cheater

Always defects. It exploits suckers immediately, but when cheaters become common they mostly inflict low-payoff mutual defection on one another.

Grudger

Cooperates until its partner defects once, then defects for the rest of that repeated match. It can sustain cooperation with itself while punishing cheaters after first contact.

Evolution Step

Each generation consists of random repeated matches, score accumulation, then fitness-proportionate reproduction with mutation. The point is not exact biology, but the strategic logic of repeated interaction.