Mind the gap – moving beyond the dichotomy between intentional gestures and emotional facial and vocal signals of nonhuman primates

Abstract

Despite the variety of theories suggesting how human language might have evolved, very few consider the potential role of emotions in such scenarios. The few existing theories jointly highlight that gaining control over the production of emotional communication was crucial for establishing and maintaining larger social groups. This in turn resulted in the development of more complex social emotions and the corresponding sophisticated socio-cognitive skills to understand others’ communicative behavior, providing the grounds for language to emerge. Importantly, these theories propose that the ability of controlling emotional communication is a uniquely human trait, an assumption that we will challenge. By taking a comparative approach, we discuss recent findings from behavioral and neurobiological studies from our closest relatives, the non-human primates, on the extent of control over their gestural, facial and vocal signals. This demonstrates that research foci differ drastically across these modalities, which further enhances the traditional dichotomy between emotional, involuntary facial and vocal expressions in contrast to intentionally, voluntarily produced gestures. Based on this brief overview, we point to gaps of knowledge in primate communication research and suggest how investigating emotional expressions in our closest relatives might enrich the road map towards the evolution of human language.

Multimodal communication and language origins: integrating gestures and vocalizations

“…The study of intentional communication in non‐human animals started out as an endeavour in the gestural modality (Liebal & Oña, ). Tomasello et al .…”

“…The study of intentional communication in non-human animals started out as an endeavour in the gestural modality (Liebal & Oña, 2018). Tomasello et al (1985) and used a Grice-inspired approach to develop criteria for potentially intentional communication in the gestural modality in great apes.…”

Primate communication: Affective, intentional, or both?

“…More recently, voices in the field of primatology (Graham, Wilke, Lahiff, & Slocombe, 2019;Kret, Prochazkova, Sterck, & Clay, 2020;Liebal & Oña, 2018;Townsend et al, 2017) have returned to question again whether such a dichotomous view of primate communication is biologically meaningful and argue that instead, such views may hamper progress in understanding the proximate and ultimate explanations that shape primate signaling. Two fundamental problems are discussed; the first is that different signal components (i.e.…”

“…Two fundamental problems are discussed; the first is that different signal components (i.e. vocal, facial, gestural) are still primarily studied in isolation rather than together as multimodal/multicomponent signal displays, despite the latter being more ecologically valid (Liebal & Oña, 2018; 5 Some scholars have suggested that our capacity for intentional emotion communication, paired with the evolution of greater emotional granularity in the way we construct emotional states (Feldman Barrett, 2017), laid the foundations for the evolution of language (Turner, 1996) as well as for hyper-cooperation and morality (Eisenberg, 2000).…”

“…Finally, to provide a holistic account of emotion communication in humans and other primates, we contend, like other researchers (Fröhlich, Sievers, Townsend, Gruber, & van Schaik, 2019;Liebal et al, 2013;Waller et al, 2013), that primate communication research should by default be multimodal (considering all sensory signal channels relevant to primates, notably the visual, acoustic, tactile, and the olfactory channel) as well as multi-componential. The latter implies considering all possible signal components (facial expressions, vocalizations, gestures) as potentially representative of emotional states (Liebal & Oña, 2018).…”