Title: The formation of institutions in communicating individuals who develop with social interactions Authors: Takashi Hashimoto(1) and Susumu Egashira(2) (1) School of Knowledge Science, Japan Advanced Institute of Science and Technology (JAIST) (2) Otaru University of Commerce Abstract: In this study, we consider the formation of institutions with a multi-agent model in which agents having simple cognitive frameworks communicate with each other. Based on the discussion of information transmission and a function of institutions, we introduce a notion of socially developmental individuals as the basic thought of humans in social sciences. The notion is that cognitive frameworks of individuals develop through interaction with other individuals. We construct a multi-agent model postulating this notion. The agent in the model has a cognitive framework that develops under the influence of others' behaviour. The framework is used to interpret signals given to the individual. Thus, it determines a way of thinking. We report the results of computer simulations of the model, especially, how institutions in agents' society are affected by some factors such as the strength of interaction between agents, the provability of errors in interpretation process, and the extent of social construction of facts.