The Washington PostDemocracy Dies in Darkness

How tiny, individual biases have huge cumulative effects on racial segregation

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Don’t want to be the odd person out in your neighborhood? A new interactive created by Vi Hart and Nicky Case shows how even very small individual biases can quickly result in racially segregated neighborhoods.

Called “The Parable of Polygons,” their fun, interactive post is part story and part game. It’s about a society of triangles and squares who are all only very slightly “shapist”: They actually prefer living in diverse neighborhoods, but they also demand that a certain proportion of their neighborhood are like them. The game starts with one simple rule: Shapes want to move if less than 1/3 of their neighbors are the same shape as them. The object of the game is to drag and drop unhappy polygons until they are all in a position that makes them happy.

Having 30 percent of your neighbors be similar to you sounds like a reasonable request, right? And one that many people might agree with. Playing the game, however, you can soon see that even a slight preference like this very quickly leads to totally segregated neighborhoods.

“Sometimes a neighborhood just becomes square, and it's not their fault if no triangles wanna stick around. And a triangular neighborhood would welcome a square, but they can't help it if squares ain't interested,” the story says.

Hart and Case’s piece is based on a well-known model from game theory, Nobel-Prize winning economist Thomas Schelling’s model of racial segregation. Schelling used the more low-tech method of pennies and nickels on graph paper, moving them one-by-one if they were in an “unhappy” situation.

As for Hart and Case’s model, Schelling’s theory had a few major findings. First, that society as a whole can appear deeply racist and divided, even if individual members have only very slight biases. Second, that the initial starting conditions for the game matter: If a neighborhood begins the game highly segregated, it is far more likely to remain that way. Say Hart and Case, “Your bedroom floor doesn’t stop being dirty just coz you stopped dropping food all over the carpet.” And third, that intervention is often necessary to maintain diversity.

Unlike Schelling’s work, Hart and Case add a happy ending. Their model shows how even a small cultural demand for diversity can have a large cumulative effect, just as slight biases do. If people refuse to live (or work, or study) in racially homogenous environments, segregation rapidly breaks down. The message is a powerful one: Equality takes work, but demanding diversity is a powerful tool to accomplish it.