Conventional behaviors develop from practice for regularly occurring problems of coordination within a community of actors. Reusing and extending conventional methods for coordinating behavior is the task of everyday reasoning.The computational model presented in the paper details the emergence of convention in circumstances where there is no ruling body of knowledge developed by prior generations of actors within the community to guide behavior. The framework we assume combines social theories of cognition with human information processing models that have been developed (...) within Cognitive Science. The model presented reflects both elements of the framework. Conventional behaviors are partially coded in the predisposition of participants in a joint activity to expect certain points of coordination to develop during the course of the activity. The expected points of coordination that are commonly assumed form a design for an activity. Because of uncertainty, interruptions, and numerous other opportunities to get off‐track and out‐of‐synch, the participants must work jointly and continuously to achieve conventional coordination.One feature of the model is that the community improves its performance despite the fact that individual actors reason independently about their experiences. Another important feature of the model is that the mechanisms for improving behavior are tied to the memory function of individual actors. A third important feature is that the social interaction among the participants simplifies and drives the everyday reasoning processes. An analysis of a large set of computational experiments supports the theoretical position that is developed regarding everyday reasoning and convention. (shrink)