Field Guide · models · emergence & computation
Schelling's segregation
A gentle wish, a brutal outcome.
In 1971 the economist Thomas Schelling asked what would happen if people had only a mild preference about their neighbours — not wanting to be surrounded by their own kind, just not wanting to be a small minority. The intuition says: mild preference, mild outcome. The intuition is wrong.
Set the threshold to a third — each agent is content as long as a third of its neighbours are similar — and the grid still slides into near-total segregation. The collective pattern is far more extreme than any individual wanted. No one designed it; it emerges from everyone adjusting locally, and once it forms it is stable, because everyone is now content.
This is the model I keep in mind whenever a system produces an outcome no one in it intended. The macro state is not the sum of the micro wishes — it is what those wishes, interacting, happen to settle into. Aggregate behaviour is its own thing, and you cannot read it off the preferences of the parts.