Anna Roberts, Sam G. B. Roberts

Mammals living in more complex social groups typically have large brains for their body size and many researchers have proposed that the primary driver of the increase in brain size through primate and hominin evolution are the selection pressures associated with sociality. Many mammals, and especially primates, use flexible signals that show a high degree of voluntary control and these signals may play an important role in maintaining and coordinating interactions between group members. However, the specific role that cognitive skills play in this complex communication, and how in turn this relates to sociality, is still unclear. The hypothesis for the communicative roots of complex sociality and cognition posits that in socially complex species, conspecifics develop and maintain bonded relationships through cognitively complex communication more effectively than through less cognitively complex communication. We review the research evidence in support of this hypothesis and how key features of complex communication such as intentionality and referentiality are underpinned by complex cognitive abilities. Exploring the link between cognition, communication and sociality provides insights into how increasing flexibility in communication can facilitate the emergence of social systems characterized by bonded social relationships, such as those found in primates and humans. To move the field forward and carry out both the within and between species comparisons, we advocate the use of social network analysis, which provides a novel way to describe and compare social structure. Using this approach can lead to a new, systematic way of examining social and communicative complexity across species, something that is lacking in current comparative studies of social structure.