What sustains cultural diversity and what undermines it? Axelrod and beyond

We relax a simplification of Axelrod's (1997) model of cultural dissemination that has not yet been studied, the assumption that all cultural states are nominal. We integrate metric states into the original model. Computational experiments demonstrate that metric states undermine cultural diversity, even without noise, by creating sufficient overlap between agents for mutual influence. We then show how adding "bounded confidence" - a recent innovation in models of social influence - allows cultural diversity to persist. However, further experiments reveal that the solution is fragile. Diversity can be sustained only with a relatively small number of metric states, low levels of noise or narrow confidence intervals.