Visually attending to a video together facilitates great ape social closeness

Visually attending to a video together facilitates great ape social closeness. Wouter Wolf and Michael Tomasello. Proceedings of the Royal Society B, Volume 286, Issue 1907, July 17 2019. https://doi.org/10.1098/rspb.2019.0488

Abstract: Humans create social closeness with one another through a variety of shared social activities in which they align their emotions or mental states towards an external stimulus such as dancing to music together, playing board games together or even engaging in minimal shared experiences such as watching a movie together. Although these specific behaviours would seem to be uniquely human, it is unclear whether the underlying psychology is unique to the species, or if other species might possess some form of this psychological mechanism as well. Here we show that great apes who have visually attended to a video together with a human (study 1) and a conspecific (study 2) subsequently approach that individual faster (study 1) or spend more time in their proximity (study 2) than when they had attended to something different. Our results suggest that one of the most basic mechanisms of human social bonding—feeling closer to those with whom we act or attend together—is present in both humans and great apes, and thus has deeper evolutionary roots than previously suspected.

1. Introduction

Humans create and maintain social relationships in ways that are seemingly unique in the animal kingdom. Specifically, humans are able to create social closeness through all kinds of shared activities and experiences that do not require direct physical interaction but instead seem to satisfy a fundamental need to share the experience with other individuals [1]. Although the precise psychological mechanisms through which such activities result in social closeness remain unclear, humans have been shown to connect with one another by doing such things as making music together [2], acting together in synchrony [3], dancing together [4,5], playing team sports together [6] or by sharing experiences through gossip [7] or attitudes [8], or disclosing personal information [9]. In a recent study, Wolf et al. [10] demonstrated that even after a minimal shared interaction in which participants were attending to the same thing without otherwise communicating, they reported feeling closer to that participant [11].

Throughout the animal kingdom, the individuals of many species act in coordination with conspecifics. For example, dolphins often behave in synchrony [12], many bird species coordinate their song and dance in a mating context [13,14], and great apes travel together [15] and sometimes hunt monkeys together [16]. But do behavioural interactions in which individuals focus on an external stimulus together create stronger social relationships or bonds between participants? To our knowledge, there are no studies examining such a relationship in any non-human species, and indeed some theorists have suggested that this method of social bonding might be uniquely human [5,10].

As always in comparison with humans, great apes are a special case because of their close phylogenetic connection. Operational definitions of social closeness (bonding) in great ape research usually rely on interactions involving physical closeness (e.g. grooming and physical play [17–19] and/or spatial proximity [20]. However, given that apes do engage in a variety of coordinated (and even to some degree cooperative activities) such as building and fighting in coalitions and alliances [21], as well as travelling and hunting in groups [22], the question is whether, like humans, great apes have evolved a psychological mechanism that leads them to create social closeness with others through shared experiences. On the other hand, it might be that connecting with others through shared experiences is a uniquely human phenomenon.

To answer this question, we adapted Wolf et al.’s [10] paradigm for apes and conducted two studies in which participants shared the experience of attending to a video together with a human experimenter (study 1) or a conspecific (study 2). In the control condition, a human experimenter (study 1) or conspecific (study 2) sat in the same place but was not watching the video. We then compared the apes' subsequent behaviour towards their partner—approaching and/or remaining in physical proximity—between the two conditions.