Vocal–gestural combinations in infant bonobos: new insights into signal functional specificity

Age differences in bonobo (Pan paniscus) multimodal communication signals

While spoken language is unique to humans, many features of human communication are shared with great apes, including the use of signals in multiple modalities such as vocalizations, gestures, and facial expressions. Communication signals can be unimodal (involving a single modality) or multimodal (combining multiple modalities simultaneously). Here, we examined age-related differences in bonobo (Pan paniscus) unimodal and multimodal communication signals. We assessed all vocalizations, gestures, facial expressions, and multimodal combinations produced by captive bonobos across a variety of behavioral contexts. All occurrences of communication signals were collected via focal observations from 12 individuals ranging from 6 months to 44 years of age. All individuals produced multimodal communication signals but all bonobos, regardless of age, produced multimodal signals at lower frequencies than unimodal signals. Age had a significant effect with younger bonobos producing more multimodal signals than older individuals (p < 0.001). The infant and juveniles produced the most multimodal signals and there was an approximately 6% increase in unimodal signals per age year increase. These findings indicate a developmental shift toward unimodal signals as bonobos age. Behavioral context was predictive of signal type usage with an increase of multimodal signals in agonistic (p < 0.001), play (p < 0.001), and sexual contexts (p = 0.001). This indicates that context is important for bonobo modality with multimodal signaling occurring more in "high-risk/high-reward" contexts where proper signal comprehension is vital. This study represents an overview of multimodal communication across bonobo life stages, offering further insights into primate communication patterns and developmental trajectories.

Multimodal communication and audience directedness in the greeting behaviour of semi-captive African savannah elephants

Many species communicate by combining signals into multimodal combinations. Elephants live in multi-level societies where individuals regularly separate and reunite. Upon reunion, elephants often engage in elaborate greeting rituals, where they use vocalisations and body acts produced with different body parts and of various sensory modalities (e.g., audible, tactile). However, whether these body acts represent communicative gestures and whether elephants combine vocalisations and gestures during greeting is still unknown. Here we use separation-reunion events to explore the greeting behaviour of semi-captive elephants (Loxodonta africana). We investigate whether elephants use silent-visual, audible, and tactile gestures directing them at their audience based on their state of visual attention and how they combine these gestures with vocalisations during greeting. We show that elephants select gesture modality appropriately according to their audience's visual attention, suggesting evidence of first-order intentional communicative use. We further show that elephants integrate vocalisations and gestures into different combinations and orders. The most frequent combination consists of rumble vocalisations with ear-flapping gestures, used most often between females. By showing that a species evolutionarily distant to our own primate lineage shows sensitivity to their audience's visual attention in their gesturing and combines gestures with vocalisations, our study advances our understanding of the emergence of first-order intentionality and multimodal communication across taxa.

GesturalOrigins: A bottom-up framework for establishing systematic gesture data across ape species

Current methodologies present significant hurdles to understanding patterns in the gestural communication of individuals, populations, and species. To address this issue, we present a bottom-up data collection framework for the study of gesture: GesturalOrigins. By "bottom-up", we mean that we minimise a priori structural choices, allowing researchers to define larger concepts (such as 'gesture types', 'response latencies', or 'gesture sequences') flexibly once coding is complete. Data can easily be re-organised to provide replication of, and comparison with, a wide range of datasets in published and planned analyses. We present packages, templates, and instructions for the complete data collection and coding process. We illustrate the flexibility that our methodological tool offers with worked examples of (great ape) gestural communication, demonstrating differences in the duration of action phases across distinct gesture action types and showing how species variation in the latency to respond to gestural requests may be revealed or masked by methodological choices. While GesturalOrigins is built from an ape-centred perspective, the basic framework can be adapted across a range of species and potentially to other communication systems. By making our gesture coding methods transparent and open access, we hope to enable a more direct comparison of findings across research groups, improve collaborations, and advance the field to tackle some of the long-standing questions in comparative gesture research.

Object use in communication of semi-wild chimpanzees

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.

On thresholds: signs, symbols and significance

Purpose

This paper reviews research developments in semiosis (sign activity) as theorized by Peirce, Eco and Sebeok, focusing specifically on the current study of “semiotic threshold zones,” which range from the origins of life through various nonhuman life forms to artificial life forms, including those symbolic thresholds most familiar to library and information science (LIS) researchers. The intent is to illustrate potential opportunities for LIS research beyond its present boundaries.

Design/methodology/approach

The paper provides a framework that describes six semiotic threshold zones (presemiotic, protosemiotic, phytosemiotic, zoosemiotic, symbolic and polysemiotic) and notable work being done by researchers in each.

Findings

While semiotic researchers are still defining the continuum of semiotic thresholds, this focus on thresholds can provide a unifying framework for significance as human and nonhuman interpretations of a wide variety of signs accompanied by a better understanding of their relationships becomes more urgent in a rapidly changing global environment.

Originality/value

Though a variety of semiotic-related topics have appeared in the LIS literature, semiotic thresholds and their potential relationships to LIS research have not been previously discussed there. LIS has traditionally tasked itself with the recording, dissemination and preservation of knowledge, and in a world that faces unprecedented environmental and global challenges for all species, the importance of these thresholds may well be considered as part of our professional obligations in potentially documenting and archiving the critical differences in semiosis that extend beyond purely human knowledge.

Congratulations to Animal Cognition on its 50th birthday! Some thoughts on the last 50 years of animal cognition research

In this article, the author reflects on some of the key issues that have arisen in comparative cognition and the role and impact of the journal Animal Cognition through its first 25 years by pretending to look back at this period from the year 2047. Successes within comparative cognition are described and the role that Animal Cognition has played in the growth of comparative cognition are discussed. Concerns are presented about issues that affect the opportunities that researchers have to work with nonhuman species and to produce good comparative cognitive science. Prescriptions for what the author hopes will happen next also are offered all in the lens of a prospectively imagined retrospective on this field.

Turn-taking skills in mammals: A systematic review into development and acquisition

How human language evolved remains one of the most intriguing questions in science, and different approaches have been used to tackle this question. A recent hypothesis, the Interaction Engine Hypothesis, postulates that language was made possible through the special capacity for social interaction involving different social cognitive skills (e.g., joint attention, common ground) and specific characteristics such as face-to-face interaction, mutual gaze and turn-taking, the exchange of rapid communicative turns. Recently, it has been argued that this turn-taking infrastructure may be a foundational and ancient mechanism of the layered system of language because communicative turn-taking has been found in human infants and across several non-human primate species. Moreover, there is some evidence for turn-taking in different mammalian taxa, especially those capable of vocal learning. Surprisingly, however, the existing studies have mainly focused on turn-taking production of adult individuals, while little is known about its emergence and development in young individuals. Hence, the aim of the current paper was 2-fold: First, we carried out a systematic review of turn-taking development and acquisition in mammals to evaluate possible research bias and existing gaps. Second, we highlight research avenues to spur more research into this domain and investigate if distinct turn-taking elements can be found in other non-human animal species. Since mammals exhibit an extended development period, including learning and strong parental care, they represent an excellent model group in which to investigate the acquisition and development of turn-taking abilities. We performed a systematic review including a wide range of terms and found 21 studies presenting findings on turn-taking abilities in infants and juveniles. Most of these studies were from the last decade, showing an increased interest in this field over the years. Overall, we found a considerable variation in the terminologies and methodological approaches used. In addition, studies investigating turn-taking abilities across different development periods and in relation to different social partners were very rare, thereby hampering direct, systematic comparisons within and across species. Nonetheless, the results of some studies suggested that specific turn-taking elements are innate, while others are acquired during development (e.g., flexibility). Finally, we pinpoint fruitful research avenues and hypotheses to move the field of turn-taking development forward and improve our understanding of the impact of turn-taking on language evolution.

Flexible signalling strategies by victims mediate post-conflict interactions in bonobos

Compared to other animals, humans supposedly excel at voluntarily controlling and strategically displaying emotional signals. Yet, new data shows that nonhuman great apes' emotion expressions may also be subject to voluntary control. A key context to further explore this is during post-conflict (PC) periods, where signalling by distressed victims may influence bystander responses, including the offering of consolation. To address this, our study investigates the signalling behaviour of sanctuary-living bonobo victims following aggression and its relation to audience composition and PC interactions. Results show that the production of paedomorphic signals by victims (regardless of age) increased their chances of receiving consolation. In adults, the production of such signals additionally reduced the risk of renewed aggression from opponents. Signal production also increased with audience size, yet strategies differed by age: while immatures reduced signalling in proximity of close-social partners, adults did so especially after receiving consolation. These results suggest that bonobos can flexibly adjust their emotion signalling to influence the outcome of PC events, and that this tendency has a developmental trajectory. Overall, these findings highlight the potential role that flexible emotion communication played in the sociality of our last common ancestor with Pan. This article is part of the theme issue 'Cognition, communication and social bonds in primates'.

Visual bodily signals as core devices for coordinating minds in interaction

The view put forward here is that visual bodily signals play a core role in human communication and the coordination of minds. Critically, this role goes far beyond referential and propositional meaning. The human communication system that we consider to be the explanandum in the evolution of language thus is not spoken language. It is, instead, a deeply multimodal, multilayered, multifunctional system that developed-and survived-owing to the extraordinary flexibility and adaptability that it endows us with. Beyond their undisputed iconic power, visual bodily signals (manual and head gestures, facial expressions, gaze, torso movements) fundamentally contribute to key pragmatic processes in modern human communication. This contribution becomes particularly evident with a focus that includes non-iconic manual signals, non-manual signals and signal combinations. Such a focus also needs to consider meaning encoded not just via iconic mappings, since kinematic modulations and interaction-bound meaning are additional properties equipping the body with striking pragmatic capacities. Some of these capacities, or its precursors, may have already been present in the last common ancestor we share with the great apes and may qualify as early versions of the components constituting the hypothesized interaction engine. This article is part of the theme issue 'Revisiting the human 'interaction engine': comparative approaches to social action coordination'.

Revisiting the human 'interaction engine': comparative approaches to social action coordination

The evolution of language was likely facilitated by a special predisposition for social interaction, involving a set of communicative and cognitive skills summarized as the 'interaction engine'. This assemblage seems to emerge early in development, to be found universally across cultures, and to enable participation in sophisticated joint action through the addition of spoken language. Yet, new evidence on social action coordination and communication in nonhuman primates warrants an update of the interaction engine hypothesis, particularly with respect to the evolutionary origins of its specific ingredients. However, one enduring problem for comparative research results from a conceptual gulf between disciplines, rendering it difficult to test concepts derived from human interaction research in nonhuman animals. The goal of this theme issue is to make such concepts accessible for comparative research, to promote a fruitful interdisciplinary debate on social action coordination as a new arena of research, and to enable mutual fertilization between human and nonhuman interaction research. In consequence, we here consider relevant theoretical and empirical research within and beyond this theme issue to revisit the interaction engine's shared, convergently derived and uniquely derived ingredients preceding (or perhaps in the last case, succeeding) human language. This article is part of the theme issue 'Revisiting the human 'interaction engine': comparative approaches to social action coordination'.

Bared-teeth displays in bonobos (Pan paniscus): An assessment of the power asymmetry hypothesis

Facial expressions are key to navigating social group life. The Power Asymmetry Hypothesis of Motivational Emancipation predicts that the type of social organization shapes the meaning of communicative displays in relation to an individual's dominance rank. The bared-teeth (BT) display represents one of the most widely observed communicative signals across primate species. Studies in macaques indicate that the BT display in despotic species is often performed unidirectionally, from low- to high-ranking individuals (signaling submission), whereas the BT display in egalitarian species is usually produced irrespective of dominance (mainly signaling affiliation and appeasement). Despite its widespread presence, research connecting BT displays to the power asymmetry hypothesis outside the Macaca genus remains scarce. To extend this knowledge, we investigated the production of BT in relation to social dominance in dyadic interactions (N = 11,377 events) of 11 captive bonobos (Pan paniscus). Although adult bonobos were more despotic than previously suggested in the literature, BT displays were produced irrespective of dominance rank. Moreover, while adults produced the BT exclusively during socio-sexual interactions, especially during periods of social tension, immature bonobos produced the BT in a wider number of contexts. As such, the results indicate that the communicative meaning of the BT display is consistent with signaling appeasement, especially in periods of social tension. Moreover, the BT display does not seem to signal social status, supporting the prediction for species with a high degree of social tolerance. These results advance our understanding of the origins of communicative signals and their relation to species' social systems.

Exploring greetings and leave-takings: communication during arrivals and departures by chimpanzees of the Bossou community, Guinea

In human fission-fusion societies, ritualized non-linguistic signal exchanges that include gestures, vocalizations, and facial expressions are regularly observed at both arrivals (greetings) and departures (leave-takings). These communicative events play an important role in the formation and maintenance of social relationships. Wild chimpanzees also form large communities that split into smaller fluid parties during daily activities, with individuals moving freely between them. However, in chimpanzees only greetings have been reported. This study explores signal exchanges in the Bossou chimpanzee community during fissions (departures) and fusions (arrivals) given an individual's social rank, kinship, position as traveller or party-member, the level of potential threat, and the party size and presence of mature males. We analysed three time periods (1993-1994; 2003-2004; 2013-2014) during which the composition and social hierarchy of the community varied. We show that the occurrence and form of communication during fission and fusion events are mediated by social factors, including rank, kinship, and party size and composition. Individuals were more likely to communicate during fusions than during fissions, communication was more likely to be produced towards a higher-ranking individual and to non-kin individuals, but the tendency to communicate in general increased with an increase in social rank. The presence of more individuals, and in particular mature males, decreased the likelihood of communication. Communication during fusions supported patterns reported in previous studies on greetings, and our results support the argument that, if present, leave-takings are not a common feature of chimpanzee social interactions. Current methodological difficulties regarding the function of declarative signals hinder our ability to discriminate potential parting rituals within communication before departures. Given similar methodological difficulties, we also provide a note of caution in the interpretation of all signals produced during fusions as 'greetings'.

A review of research in primate sanctuaries

While non-human primate studies have long been conducted in laboratories, and more recently at zoological parks, sanctuaries are increasingly considered a viable setting for research. Accredited sanctuaries in non-range countries house thousands of primates formerly used as subjects of medical research, trained performers or personal pets. In range countries, however, sanctuaries typically house orphaned primates confiscated from illegal poaching and the bushmeat and pet trafficking trades. Although the primary mission of these sanctuaries is to rescue and rehabilitate residents, many of these organizations are increasingly willing to participate in non-invasive research. Notably, from a scientific standpoint, most sanctuaries provide potential advantages over traditional settings, such as large, naturalistic physical and social environments which may result in more relevant models of primates' free-ranging wild counterparts than other captive settings. As a result, an impressive scope of research in the fields of primate behaviour, cognition, veterinary science, genetics and physiology have been studied in sanctuaries. In this review, we examine the range and form of research that has been conducted at accredited sanctuaries around the world. We also describe the potential challenges of sanctuary-based work and the considerations that external researchers may face when deciding to collaborate with primate sanctuaries on their research projects.

Developmental perspectives on primate gesture: 100 years in the making

This paper is an introduction to the special issue entitled Evolving the study of gesture: evaluating and unifying theories of gesture acquisition in great apes. The gestures of great apes have been recorded in scientific literature for over 100 years, but the ways in which apes acquire their gestures remains a highly debated topic. Through this historical framework, we summarize and contextualize contemporary research on the development of ape gesture. We describe the papers presented in this special issue, grouping them into three themes: assessing theories, methodological innovation, and new empirical approaches. Each of the papers is a significant contribution to the literature on ape gesture, but the collection of work together represents a unique collaboration across labs, theories, and studied species. By considering the papers side-by-side, we hope that readers will see the authors as engaging in a true dialogue, one which will help the field of primate gesture research make significant advances in the years to come.

Gesturing towards the future: cognition, big data, and the future of comparative gesture research

The field of ape gesture research has grown significantly in the past two decades, but progress on the question of gesture development has been limited by methodological and terminological disagreements, small sample sizes, and a lack of fine-grained longitudinal data. The main theories of gesture acquisition are often portrayed as mutually exclusive, but only some theories actually detail learning mechanisms, and differences in the level of analysis may help explain some of the apparent disagreements. Gesture research would benefit greatly from the articulation of more testable hypotheses. We propose two hypotheses that follow from dominant theories of gesture acquisition. We urge scholars to collect new data and leverage existing data in ways that maximize the potential for comparison across datasets and articulation with studies of other communicative modalities. Finally, we advocate for a transition away from using intentionality as a marker of the 'special status' of gesture, and towards using gesture as a window onto the lives and minds of apes.