Gestural repertoire size is associated with social proximity measures in wild chimpanzees

Abstract

Gestural repertoire size is associated with social proximity measures in wild chimpanzees. http://researchonline.ljmu.ac.uk/id/eprint/10324/ Article LJMU has developed LJMU Research Online for users to access the research output of the University more effectively. Abstract 1Studying the communication systems of primates can provide insights into the evolutionary 2 origins of human language. Some theories propose that language evolved to help meet the 3 demands of managing complex social relationships. Examining the associations between 4 sociality and communication in the great apes can help to identify the specific selection 5 pressures that may have been important for language evolution. In particular, gestural 6 communication is believed to be important because it is a relatively recent trait seen only in 7 primates and particularly in the great apes. However, the extent to which more complex 8 gestural communication plays a role in managing social relationships, as compared to less 9 complex gestural communication, is not well understood. Using social network analysis, we 10 examined the association between complex gesturing (indexed as repertoire size) and 11 complexity of social relationships indexed as proximity (the duration of time spent within 10 12 m, per hour spent in same party) in wild chimpanzees (Pan troglodytes schweinfurthii). 13 Repertoire size (the total number of gesture types a focal subject produced towards other 14 individuals) and dyadic repertoire size (the number of gesture types produced towards the 15 dyad partner, per hour spent within 10 meters) were positively associated with proximity at 16 the level of the group (centrality in the proximity network) and the dyad (proximity duration 17 between dyads) respectively. Further, the repertoire size of visual and auditory short-range 18 gestures was positively associated with proximity, whilst the repertoire size of tactile gesture 19 was negatively associated with proximity. Overall these results suggest that gestural 20 repertoire size has important implications for maintaining social relationships in wild 21 chimpanzees and more broadly that gestural communication may have played an important 22 role in language evolution.23 24 social system 25 of social relationships in social groups [Aiello and Dunbar, 1993]. Complex social systems 32 have been defined as those in which individuals interact in many different contexts with 33 many different individuals [Freeberg et al., 2012]. In large and complex social groups, as 34 compared to smaller and less complex groups, there are more relationships to track and a 35 greater range of different types of social relationships [Dunbar and Shultz, 2010]. This means 36 that individuals in large groups spend a higher amount of their time forming and maintaining 37 social relationships with others, as compared to individuals in smaller groups. Complex 38 communication systems, defined as those which contain a larger number of structurally and 39 functionally distinct elements (e.g. a larger repert...

Chimpanzee facial gestures and the implications for the evolution of language

“…However, response waiting at the end of the signal occurred significantly below chance level for both facial expressions and manual gestures. In the gesture literature, response waiting at the end of the signal is often used as a measure of intentionality (Byrne et al, 2017;Graham et al, 2018;Roberts & Roberts, 2019;Hobaiter & Byrne, 2011), but previous studies have not quantified this variable to the extent that we did. Thus, it appears that response waiting at the end of a signal is rare and may not be as helpful for the identification of gestures when compared to other forms of response waiting.…”

“…To begin the search for facial gestures in nonhumans, we chose to study chimpanzees (Pan troglodytes) for two reasons: first, their well-described manual gestures, and second, their phylogenetic position between humans and monkeys. Firstly, the well-documented manual gestures of chimpanzees (Byrne et al, 2017;Liebal, Call & Tomasello, 2004;Leavens, Russell & Hopkins, 2005;Hobaiter, 2011;Roberts, Vick & Buchanan-Smith, 2012;Roberts, Vick & Buchanan-Smith, 2013;McCarthy, Jensvold & Fouts, 2013;Hobaiter & Byrne, 2014;Graham et al, 2018;Heesen et al, 2019;Roberts & Roberts, 2019) provide a benchmark against which to compare the characteristics of facial expressions (Fig. 1).…”

Social bonding, gestural complexity and displacement behaviour of wild chimpanzee

“…What has long puzzled anthropologists is that dominance hierarchy can sometimes lead to greater social cohesion because it enables signaller to more effectively predict outcome of the interaction before they engage in the interaction with the recipient (Flack, Girvan, De Waal, & Krakauer, 2006). Classical ethologists have shown very clearly how lack of linear dominance hierarchy can make animal societies less predictable and more aggressive (Flack, de Waal, & Krakauer, 2005) demanding complex but low intensity communication to resolve ambiguity in social relationships (A. I. Roberts et al, 2019).…”

“…I. Roberts, 2018; A. I. Roberts & S. G. B. Roberts, 2018), repertoire size (A. I. Roberts, Chakrabarti, & Roberts, 2019) and multimodality (S.…”

Coevolution of social and communicative complexity in lemurs

“…Many signals are used to establish and maintain social relationships between group members, and being able to reliably assess the behaviour of others and to respond adaptively to it is a key cognitive ability [4,8,31]. Since primates living in larger groups have more differentiated social relationships and larger brains for their body size [31], the number of signals employed to mediate social relationships might be related to cognitively complex communication strategies [8,14,63].…”