A socio-ecological perspective on the gestural communication of great ape species, individuals, and social units

Abstract

Over the last 30 years, most research on non-human primate gestural communication has been produced by psychologists, which has shaped the questions asked and the methods used. These researchers have drawn on concepts from philosophy, linguistics, anthropology, and ethology, but despite these broad influences the field has neglected to situate gestures into the socio-ecological context in which the diverse species, individuals, and social-units exist. In this review, we present current knowledge about great ape gestural communication in terms of repertoires, meanings, and development. We fold this into a conversation about variation in other types of ape social behaviour to identify areas for future research on variation in gestural communication. Given the large variation in socio-ecological factors across species and social-units (and the individuals within these groups), we may expect to find different preferences for specific gesture types; different needs for communicating specific meanings; and different rates of encountering specific contexts. New tools, such as machine-learning based automated movement tracking, may allow us to uncover potential variation in the speed and form of gesture actions or parts of gesture actions. New multi-group multi-generational datasets provide the opportunity to apply analyses, such as Bayesian modelling, which allows us to examine these rich behavioural landscapes. Together, by expanding our questions and our methods, researchers may finally be able to study great ape gestures from the perspective of the apes themselves and explore what this gestural communication system reveals about apes’ thinking and experience of their world.

Variable expression of linguistic laws in ape gesture: a case study from chimpanzee sexual solicitation

“…Interestingly, this study excluded the hold phase of a sign, limiting their analysis only to the more active stroke phase. The production of intentional gestures in apes are shaped not only by the signaller but by the interaction between signaller and recipient [ 38 , 66 ]. As a result, the duration of hold or repetition phase may be shaped by the immediate context of the specific interaction—for example, in waiting for a response by the recipient it may vary between being absent and very prolonged.…”

“…To do so will require large longitudinal datasets in which it is possible to test both between-individual variation and within-individual variation across different gesture types and sequence lengths. Similarly, there remains substantial work needed to explore variation across different socio-ecological contexts of gesture use, for example in the social relationship between the signaller and recipient [ 66 ]. The use of redundancy within specific subsets of gestural repertoire, or within specific contexts of gesture demonstrates both the importance of compression in communicative systems in general, but also the flexibility present in each specific usage.…”

Variable expression of linguistic laws in ape gesture: a case study from chimpanzee sexual solicitation

“…Interestingly, this study excluded the hold phase of a sign, limiting their analysis only to the more active stroke phase. The production of intentional gestures in apes are shaped not only by the signaller, but by the interaction between signaller and recipient (Byrne et al, 2017; Graham et al, 2022). As a result, the duration of hold or repetition phase may be shaped by the immediate context of the specific interaction – for example, in waiting for a response by the recipient it may vary between being absent and very prolonged.…”

“…To do so will require large longitudinal datasets in which it is possible to test both between-individual variation and within-individual variation across different gesture types and sequence lengths. Similarly, there remains substantial work needed to explore variation across different socio-ecological contexts of gesture use, for example in the social relationship between the signaller and recipient (Graham et al, 2022). The use of redundancy within specific subsets of gestural repertoire, or within specific contexts of gesture demonstrates both the importance of compression in communicative systems in general, but also the flexibility present in each specific usage.…”

Are ape gestures like words? Outstanding issues in detecting similarities and differences between human language and ape gesture

“…The next phase of sharpening our understanding of ape gesture meanings could therefore consider the extent to which the communicator is sensitive to broader elements of context with their recipient [ 74 ]. What if gestures, like words, are tuned to not only the immediate, but also the historic context of individual interactions?…”