Drawing on recent work in developmental and comparative psychology, this paper argues that demonstratives function to coordinate the interlocutors' joint focus of attention, which is one of the most basic functions of human communication. The communicative importance of demonstratives is reflected in a number of properties that together characterize them as a particular word class: In contrast to other closed-class expressions, demonstratives are universal, they are generally so old that their roots cannot be traced back to other linguistic items, they (...) are among the earliest words that children learn, and they are closely tied to a particular gesture. Moreover, demonstratives play an important role in the organization of discourse and the diachronic evolution of grammar, which arguably is also motivated by their communicative function to establish joint attention. (shrink)