Symbolic Signal Use in Wild Chimpanzee Gestural Communication?: A Theoretical Framework

Symbolic communication is not obvious in the natural communicative repertoires of our closest living relatives, the great apes. However, great apes do show symbolic competencies in laboratory studies. This includes the understanding and the use of human-provided abstract symbols. Given this evidence for the underlying ability, the apparent failure to make use of it in the wild is puzzling. We provide a theoretical framework for identifying basic forms of symbolic signal use in chimpanzee natural communication. In line with the laboratory findings, we concentrate on the most promising domain to investigate, namely gesture, and we provide a case study in this area. We suggest that evidence for basic symbolic signal use would consist of the presence of two key characteristics of symbolic communication, namely arbitrariness and conventionalization. Arbitrariness means that the linkage between the form of the gesture and its meaning shows no obvious logical or otherwise motivated connection. Conventionalization means that the gesture is shared at the group-level and is thus socially learned, not innate. Further, we discuss the emergence and transmission of these gestures. Demonstrating this basic form of symbolic signal use would indicate that the symbolic capacities revealed by laboratory studies also find their expression in the natural gestural communication of our closest living relatives, even if only to a limited extent. This theoretical article thus aims to contribute to our understanding of the developmental origins of great ape gestures, and hence, arguably, of human symbolic communication. It also has a very practical aim in that by providing clear criteria and by pointing out potential candidates for symbolic communication, we give fieldworkers useful prerequisites for identifying and analyzing signals which may demonstrate the use of great apes’ symbolic capacities in the wild.

Caring from behind the face mask in healthcare: Learning from the dramatic arts

The COVID-19 pandemic has made its impact across the globe with great voracity. New routines have displaced older more established ones with ruthless efficiency—no more so than in healthcare. In meeting these challenges, many healthcare workers have had to prepare for and enact many new ways of working. Regardless of their speciality or stage of training, health professions educators (HPEs) have helped train our healthcare workforce in developing new skills with great tempo. Throughout all of these efforts one constant has guided our endeavours—the humane connection with those that provide and those that seek healthcare.However, with COVID-19 we have had to distance ourselves from our patients, and colleagues, and clad ourselves in various items of personal protection equipment (PPE). The protective barrier also acts as a barrier to personal interaction and therefore presents challenges in how we connect with each other on a humane level. Few disciplines have engaged with the complexities of verbal and gestural communication as thoroughly and consistently as the dramatic arts. Actors in Ancient Greece would perform wearing masks and used oratory as well as gestural communication to enrapture the audience.Drawing upon the dramatic arts, we aim to explore the relationship between face and mask and thereby provide reflective insights for HPEs to help guide healthcare workers in their communication from behind the face mask.

Linguistic laws are not the law in chimpanzee sexual solicitation gestures.

Two language laws have been identified as manifestations of universal principles of animal behaviour, both acting on the organisation of numerous vocal and behavioural communicative systems. Zipf's law of brevity describes a negative relationship between behavioural length and frequency of behaviour. Menzerath's law defines a negative correlation between the number of behaviours in a sequence and average length of the behaviour composing it. Both laws have been linked with the information-theoretic principle of compression, which tends to minimise code length. We investigate the presence of these two laws in the repertoire of chimpanzee sexual solicitation gestures. We find that chimpanzee solicitation gestures do not follow either Zipf's law of brevity or Menzerath's law consistently. For the second time in ape gestural communication, evidence supporting Zipf's law of brevity was absent, and, here, the presence of Menzerath's law appears individually driven. Ape gesture does not appear to manifest a principle of compression or pressure for efficiency that has been previously proposed to be universal. Importantly, the same signals were shown to adhere to these laws when used in a different behavioural context; highlighting that signallers consider signalling efficiency broadly, and diverse factors play important roles in shaping investment in signal production.

A Comparison of Focal and Opportunistic Sampling Methods when Studying Chimpanzee Facial and Gestural Communication

Researchers frequently use focal individual sampling to study primate communication. Recent studies of primate gestures have shown that opportunistic sampling offers benefits not found in focal individual sampling, such as the collection of larger sample sizes. What is not known is whether the opportunistic method is biased towards certain signal types or signalers. Our goal was to assess the validity of the opportunistic method by comparing focal individual sampling to opportunistic sampling of facial and gestural communication in a group of captive chimpanzees (<i>Pan troglodytes</i>). We compared: (1) the number of observed facial and gestural signals per signal type and (2) the number of observed facial and gestural signals produced by each signaler. Both methods identified facial signals, gesture signals, and gesture signalers at similar relative rates, but the opportunistic sampling method yielded a more even distribution of signalers and signal types than the focal individual sampling method. In addition, the opportunistic sampling method resulted in larger sample sizes for both facial and gestural communication. However, the opportunistic method did not allow us to calculate the signals per time for each individual, which is easily done with the focal individual method. These results suggest that the opportunistic sampling method is (1) comparable to the focal individual sampling method in multiple important measures, (2) associated with additional sampling benefits, and (3) limited in measuring some variables. Thus, we recommend that future studies use a mixed-methods approach, as focal individual and opportunistic sampling have distinct strengths that complement each other’s limitations.

On the Gestural Origin of Language Lateralisation: Manual Communication reflects Broca’s Asymmetry in Monkeys

Manual gestures and speech recruit a common neural network, involving Broca area in the left hemisphere. Evolutionary questions about this language organization led to a renewed attention for comparative research on gestural communication in our closer primate relatives and its potential language-like features. Here, using in vivo anatomical MRI in 80 baboons, we found that communicative gesturing’s lateralisation – but not handedness for manipulation - is related to Broca homologue’s marker in monkeys, namely contralateral depth hemispheric asymmetry of the ventral portion of the inferior arcuate sulcus. This finding provides strong support for the gestural evolutionary continuities with language-related frontal specialization, dating back not only to Homo sapiens evolution, but rather to a much older common ancestor shared with old-world monkeys, 25-35 million years ago.

Social hyperscanning with fNIRS

The interest of neuroscience has been aimed at the investigation of the neural bases underlying gestural communication. This research explored the intra- and inter-brain connectivity between encoder and decoder. Specifically, adopting a “hyperscanning paradigm” with the functional Near-infrared Spectroscopy (fNIRS) cerebral connectivity in oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin levels were revealed during the reproduction of affective, social, and informative gestures of different valence. Results showed an increase of intra- and inter-brain connectivity in dorsolateral prefrontal cortex for affective gestures, in superior frontal gyrus for social gestures and in frontal eyes field for informative gestures. Moreover, encoder showed a higher intra-brain connectivity in posterior parietal areas more than decoder. Finally, an increasing of inter-brain connectivity more than intra-brain (ConIndex) was observed in left regions for positive gestures. The present research has explored how the individuals neural tuning mechanisms turn out to be strongly influenced by the nature of specific gestures.