LAUSR

In his comment on Axelrod et al. (1), de Marchi (2) complains that our model of polarization leaves out a number of mechanisms of opinion change and that consequentially the model cannot be used to guide public policy. However, the purpose of the model is to gain insights about what is possible over time given minimal assumptions about attraction and repulsion. Keeping models simple to gain insight rather than comprehensive enough to include all relevant context is a common use of agent-based models. One example is the iterated Prisoner’s Dilemma (iPD), which leaves out many mechanisms that could be important in any given setting. It is precisely because the paradigm is so simple that it is possible to identify counterintuitive possibilities that would otherwise be obscure (3). For example, in the iPD, it is possible to win a tournament without ever doing better than the actor with whom you are currently playing. Another example is Schelling’s famous segregation model (4), which shows the possibility of a population’s becoming highly segregated even if everyone is willing to stay put in a slightly integrated neighborhood. De Marchi says the results of our model are obvious from our assumptions. Here are three results that are not obvious: