  To give one example: a famous and groundbreaking agent-based simulation was Thomas Schelling’s (1971) model of “segregation.” The agents in his simulation were individuals who “lived” on a chessboard.  The individuals were divided into two groups in the society (e.g. two different races, boys and girls, smokers and non-smokers, etc.)  Each square on the board represented a house, with at most one person per house. An individual is happy if he/she has a certain percent of neighbors of his/her own group. Happy agents stay where they are, unhappy agents move to free locations. Schelling found that the board quickly evolved into a strongly segregated location pattern if the agents’ “happiness rules” were specified so that segregation was heavily favored. Surprisingly, however, he also found that initially integrated boards tipped into full segregation even if the agents’ happiness rules expressed only a mild preference for having neighbors of their own type.