Abstract
Primate social bonds are described as being especially complex in their nature, and primates have unusually large brains for their body size compared to other mammals. Communication in primates has attracted considerable attention because of the important role it plays in social bonding. It has been proposed that differentiated social relationships are cognitively complex because primates need to continuously update their knowledge about different types of social bonds. Therefore, primates infer whether an opportunity for social interaction is rewarding (valuable to individual goals) based on their knowledge of the social relationships of the interactants. However, exposure to distraction and stress has detrimental effects on the dopaminergic system, suggesting that understanding social relationships as rewarding is affected in these conditions. This paper proposes that complex communication evolved to augment the capacity to form social relationships during stress through flexibly modifying intentionality in communication (audience checking, response waiting and elaboration). Intentional communication may upregulate dopamine dynamics to allow recognition that an interaction is rewarding during stress. By examining these associations between complexity of communication and stress, we provide new insights into the cognitive skills involved in forming social bonds in primates and the evolution of communication systems in both primates and humans. This article is part of the theme issue 'Cognition, communication and social bonds in primates'.