The shape of lipsmacking: socio-emotional regulation in bearded capuchin monkeys (Sapajus libidinosus)

Great ape infants' face touching and its role in social engagement

Touch has a key role in the social development of infant primates and in the regulation of social interactions, even so, there's a rarity of studies on infants' use of social touch. In this work, we document chimpanzee infants and human infants' touching of other's faces, a behavior already described in wild capuchin monkey infants, and investigate possible functions of infants' social touch. A strength of this study is that we sampled chimpanzee and human infants from three different social ecologies each. Each infant was observed naturalistically, in their everyday environments. In 36 h of observation, we found 269 touch events, specifically 222 face touches and 47 head touches. We found significant differences between groups, within species. Face touching occurred preferentially with adult females in all groups, and preferentially in prosocial contexts, although the most preferred contexts differed across groups. A unifying concept was that almost all infant face touching occurred during joint attention events. We interpret this as the ability of 1-year-olds to use face touching as a behavioral marker of mutual engagement during bouts of triadic connectedness, that is when they engage together with a social partner about an object or an event. In this study, we document an understudied behavior of young chimpanzees and humans, one that is not only part of prosocial interactions, but one that may function to highlight infants' active role in engagement with another, while they together engage in triadic connectedness.

Conserved and differing functions of the endocrine system across different social systems - oxytocin as a case study

A key goal of the field of endocrinology has been to understand the hormonal mechanisms that drive social behavior and influence reactions to others, such as oxytocin. However, it has sometimes been challenging to understand which aspects and influences of hormonal action are conserved and common among mammalian species, and which effects differ based on features of these species, such as social system. This challenge has been exacerbated by a focus on a relatively small number of traditional model species. In this review, we first demonstrate the benefits of using non-traditional models for the study of hormones, with a focus on oxytocin as a case study in adding species with diverse social systems. We then expand our discussion to explore differing effects of oxytocin (and its response to behavior) within a species, with a particular focus on relationship context and social environment among primate species. Finally, we suggest key areas for future exploration of oxytocin's action centrally and peripherally, and how non-traditional models can be an important resource for understanding the breadth of oxytocin's potential effects.

Erratum: The shape of lipsmacking: socio-emotional regulation in bearded capuchin monkeys (Sapajus libidinosus) - CORRIGENDUM

[This corrects the article DOI: 10.1017/ehs.2023.10.].