This article examines the public at a science exhibition or festival and tries to determine whether casual visitors are a means of expanding the audience. According to a Swiss survey of public attitudes towards science (2005), the non-public of a science exhibition or festival is distinguished by demographics such as gender and education (more female and less educated), cultural practices (less frequent) and attitudes towards science (less positive). Considering the Swiss science festival of 2009, casual visitors differ from intentional ones in terms of sociodemographic aspects and scientific cultural practices; on the other hand, casual visitors are close to intentional ones in terms of non-scientific cultural practices and attitudes towards science. Consequently, casual visitors are one way of increasing audiences.

This paper relates to a special case of science-society mediation set up during the Science et Cité festival 2005. This national event took place in about twenty cities in Switzerland to promote a closer cooperation between science and society via art (theatre, music, dance, exhibitions, cinema, etc.), in order to reach the population at large. Results on the profile of the public, the role played by the cultural institutions involved, the motives of the visitors and the role of art in the science-society dialogue show that the goals aimed at by the festival's organisers were only partially reached. Moreover, the analyses shed light on the complex relation between art, science and society in public understanding of science activities.