According to David Lewis (1969), social conventions are behavioral regularities that are stable but relatively arbitrary solutions to repeated coordination problems. A paradigmatic example is using language to communicate:
- Repeated problem: using sensory data to refer to novel objects or ideas with novel partners;
- Coordination problem: understanding partners using shared expectations about mappings between linguistic forms and meanings;
- Arbitrariness: there are many possible mappings, as demonstrated by the diversity of human languages;
- Stability: it is more efficient for a community to keep using the same mapping than to generate a new one from scratch during each communicative exchange.
In contrast, Prescriptive norms are solutions to problems where coordination may not initially be in all agents’ self-interest.