This paper introduces an application using multi-agent system to model an artificial society. The work follows a field research in economics in Cameroon about the behavior of nomad herdsmen securing their access to rangelands. Two central elements were stressed: regularity in meetings and flexibility while facing problems. Experiments run through simulations, testing two rationales: choices based on the notion of cost, or herdsmen taking into account the history of meetings. The system successfully shows regular dynamics, and huge differences are observed, depending on the rationality used. We conclude on the importance of the rationality described in modeling a system.