Analysing Dunbar Circles in Facebook Groups

The impact of Online Social Networks (OSNs) on the world has changed the way people interact with each other. During the last years, the trend to build virtual communities based on common interests, also called online social groups, has affirmed. Online social groups have been studied in the past, however, several aspects concerning the relationships between the group members are still unknown. Indeed, the definition of classical friendship relations in a social network is different from the social relationships established in a group. The former are defined with the will of the users, while the latter are implicitly activated by the interactions on the common topics. In this paper, we provide an analysis of the users' relationships present in 18 heterogeneous Facebook groups and we model the interactions of a group member within the group with the concept of member network. Then, we verify that the relationships present in the personal network of a user follow the Dunbar's property, previously detected in offline and online friendship ego networks. The results show that most personal networks present three or four circles as in classical Dunbar's structure, with a size comparable to the one initially described by Dunbar.