Communicative roots of complex sociality and cognition: preface to the theme issue.

Primates live in stable social groups in which they form differentiated relationships with group members and use a range of communication including facial expressions, vocalizations and gestures. However, how these different types of communication are used to regulate social interactions, and what cognitive skills underpin this communication, is still unclear. The aim of this special issue is to examine the types of cognitive skills underpinning the flexible and complex communication that is used to maintain the bonded social relationships found in primates and humans. This article is part of the theme issue 'Cognition, communication and social bonds in primates'.