THE COMMONS — tragedy of the commons, playable
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WHAT THIS IS AND HOW TO READ IT
A model of the tragedy of the commons. Agents graze on shared grass. Each one decides how much to eat: the greedy take a lot and scorch a cell fast, the restrained take a little. The catch is that a scorched field feeds everyone worse, yet overgrazing pays off personally. The question the model asks: under what conditions does the community avoid eating itself to death?
Agents with little grass around them negotiate a quota — a pact (yellow lines). But honouring it is optional: each has an honesty gene. A cheater signs the pact and grazes at full tilt while neighbours hold back. The neighbours can catch them (odds depend on monitoring) and fine them — but punishing costs the punisher too.
Overgrazing can now kill. Grass on a stripped cell only recovers if there is grass nearby to spread back in, and agents on barren ground starve faster. So a greedy community grazes its basin into a desert and dies out, while a restrained one keeps the field alive and persists — the honesty level genuinely changes who survives.
The sliders let you probe what keeps a commons alive. Hover any of them (or tap on mobile) for a one-line explanation. Key new one: land resilience — how easily grass recovers and spreads; low values make a grazed-flat basin stay a desert, so the community can starve.
The experiment series runs many games with random parameters and shows which settings lead to survival — so you can check that the sliders genuinely change the outcome rather than just seeming to. The result is a table (CSV) and a chart: each dot is a game, green survived, red went extinct.