Laughter, play faces and mimicry in animals: evolution and social functions

Abstract

Human laughter and laugh faces show similarities in morphology and function with animal playful expressions. To better understand primordial uses and effects of human laughter and laugh faces, it is important to examine these positive expressions in animals from both homologous and analogous systems. Phylogenetic research on hominids provided empirical evidence on shared ancestry across these emotional expressions, including human laughter and laugh faces. In addition, playful expressions of animals, in general, arguably have a key role in the development of social cognitive skills, a role that may help explain their polyphyletic history. The present work examines the evolution and function of playful expressions in primates and other animals. As part of this effort, we also coded for muscle activations of six carnivore taxa with regard to their open-mouth faces of play; our findings provide evidence that these carnivore expressions are homologues of primate open-mouth faces of play. Furthermore, our work discusses how the expressions of animal play may communicate positive emotions to conspecifics and how the motor resonance of these expressions increases affiliation and bonding between the subjects, resembling in a number of ways the important social–emotional effects that laughter and laugh faces have in humans. This article is part of the theme issue ‘Cracking the laugh code: laughter through the lens of biology, psychology and neuroscience’.

Evolution of laughter from play

“…Grooming releases endogenous opioids in both human and non-human primates [ 18 , 19 ], and such pleasure perhaps could have enabled the evolution of greater bonding and play. Indeed, Davilla-Ross and Palagi [ 20 ] discuss how expressions in animal play may communicate positive emotions to individuals of the same species and discuss how the motor resonance of these expressions increases bonding between the individuals. The benefits of positive emotions in play for bonding and the benefits of play itself could have therefore led to the potential for an individual to be incapacitated through too much arousal, as too much arousal can cause significant discomfort [ 21 ].…”

Joyful by nature: approaches to investigate the evolution and function of joy in non‐human animals

“…What is needed, like a human Duchenne smile (Ekman et al ., 1990), is a reliable and reproducible expression of positive affect. Unfortunately, behavioural markers do not yet meet the bar as reliable indicators of positive emotion, but research in this area is promising (Davila‐Ross & Palagi, 2022). With a better understanding of the species‐specific nuances of posture and facial expression, aided by techniques like machine learning to code fine‐grained behaviour, these sorts of indicators may be more useful in the future.…”

Differences between Mimicking and Non-Mimicking laughter in Child-Caregiver Conversation: A Distributional and Acoustic Analysis

“…2022), i.e., laughter mimicry, commonly defined as the production of laughter within one second from the end of a previous laughter produced by an interactant. Laughter mimicry occurrence plays an important role for the unfolding of conversations (e.g., showing agreement and affiliation, jointly manage and shape meaning), as well as the establishment and maintenance of relationships (Smoski, 2004;Kurtz & Algoe, 2017), including non-human primates (Davila- Ross & Palagi, 2022). However, laughter mimicry is not a purely automatic response: it is influenced by context (Bryant, 2020), interactional partner (Smoski & Bachorowski, 2003), object of the laughter 1 (Jefferson, Sacks, & Schegloff, 1977), and by the developmental stage of the interactants.…”