Object use in communication of semi-wild chimpanzees

Abstract

Object interactions play an important role in human communication but the extent to which nonhuman primates incorporate objects in their social interactions remains unknown. To better understand the evolution of object use, this study explored how objects are used in social interactions in semi-wild chimpanzees (Pan troglodytes). We used an observational approach focusing on naturally occurring object actions where we examined their use and tested whether the production of object actions was influenced by the recipients’ visual attention as well as by colony membership. The results show that chimpanzees adjusted both the type of object used, and the modality of object actions to match the visual attention of the recipient, as well as colony differences in the use of targeted object actions. These results provide empirical evidence highlighting that chimpanzees use objects in diverse ways to communicate with conspecifics and that their use may be shaped by social factors, contributing to our understanding of the evolution of human nonverbal communication, language, and tool use.

Social uncertainty promotes signal complexity during approaches in wild chimpanzees ( Pan troglodytes verus ) and mangabeys ( Cercocebus atys atys )

“…Overall, 5.10% of approaches in chimpanzees ( n = 189) compared with 0.96% in mangabeys ( n = 68) included multisensory signal types. In chimpanzees, this mainly included using objects to make sound, such as branches, leaves, the ground, or body parts [ 56 ]. Mangabeys were 108% more likely to emit visual signals than chimpanzees (108% increase, −0.57, 95% CI [−1.1, −0.05], p− = 98.3%).…”

“…Social animals flexibly employ various strategies and signals while approaching other members of their group, including 'greeting', 'attention-getter' and 'benign intent' signals [30,[54][55][56][57]. These signals are known to regulate social relationships [58], from the negotiation of tolerance and conflict prevention to coordination or cooperation [39,55,59,60], particularly in species with high levels of fission-fusion dynamics [30,49,61].…”

Many morphs: Parsing gesture signals from the noise

“…Here we decided to do the latter, incorporating it into the gesture action level, as this tended to more closely map onto previous repertoires and simplified our set of modifiers. The relevance of object-use as a modifier might be different if this approach were applied to a different dataset, for example chimpanzees may vary their use of objects depending on their structural and acoustic properties (Fitzgerald et al, 2022;Gibson et al, 2023). Other modifiers are available in the original dataset but are often only applicable to a subset of gesture actions or cases within gesture actions (for example: finger flexion); or are rarely or never part of other primate gesture coding datasets, thereby limiting applicability of results for other users.…”