Levelling playing field: synchronization and rapid facial mimicry in dog-horse play

Feline faces: Unraveling the social function of domestic cat facial signals

Lately, there has been a growing interest in studying domestic cat facial signals, but most of this research has centered on signals produced during human-cat interactions or pain. The available research on intraspecific facial signaling with domesticated cats has largely focused on non-affiliative social interactions. However, the transition to intraspecific sociality through domestication could have resulted in a greater reliance on affiliative facial signals that aid with social bonding. Our study aimed to document the various facial signals that cats produce during affiliative and non-affiliative intraspecific interactions. Given the close relationship between the physical form and social function of mammalian facial signals, we predicted that affiliative and non-affiliative facial signals would have noticeable differences in their physical morphology. We observed the behavior of 53 adult domestic shorthair cats at CatCafé Lounge in Los Angeles, CA. Using Facial Action Coding Systems designed for cats, we compared the complexity and compositionality of facial signals produced in affiliative and non-affiliative contexts. To measure complexity and compositionality, we examined the number and types of facial muscle movements (AUs) observed in each signal. We found that compositionality, rather than complexity, was significantly associated with the social function of intraspecific facial signals. Our findings indicate that domestication likely had a significant impact on the development of intraspecific facial signaling repertoires in cats.

A review of interspecific social play among nonhuman animals

BROOKS, H.J.B. & G.M. Burghardt. A comparative review of interspecific social play among nonhuman animals. NEUROSCI BIOBEHAV REV XX(X) XXX-XXX, XXXX.- Few species play socially with another species, hereafter called interspecific social play (ISP). ISP involves reading and responding appropriately to social cues of other species, often taxonomically remote, and has implications for perception, communication, and cognition. We reviewed information on non-human ISP from both print media and videos from YouTube and Reddit. We found over 200 instances of ISP. The literature predominantly featured wild primates, carnivores, and marine mammals. Carnivores and terrestrial ungulates were common in videos. ISP in avian and reptile species were found in both sources, including instances of playing with mammals. Animals may engage in ISP because it is risky and stimulating, they lack age-appropriate conspecifics, the play motivation is high, or to maintain social bonds in mixed-species groups. Cataloguing ISP uncovers which species are interacting and how. Systematic studies of ISP are difficult and many reports are brief and anecdotal. Minimally, future research should record information about each observation, including the age, sex, and history of participants.

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

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'.

Interdisciplinary approach of Yalom's group therapy factors: A theoretical model for including animal presence in social work education and practice

An increasing number of studies in the field of Social Work (SW) address the incorporation of animal presence in practice and improved understanding of social support and therapeutic components. Education programs on the ethical and practical principles of animal-assisted interventions, including models and theories supporting the psycho-physiological effects of human-animal interactions (HAI), are being implemented around the world, especially in the US. While designing and implementing a new interdisciplinary curriculum can be time-consuming and, depending on the many variables, integrating elements of HAI components in existing curricula can be a more efficient approach. We present a step-by-step approach for inclusion of HAI knowledge and practice in teaching Yalom's principles and therapeutic factors of group therapy to SW students. Based on a qualitative analysis of the existent literature and on the results of several research projects in the field of HAI, we propose an approach for infusing research-informed examples and theories supporting the beneficial effects of HAI in the direction of the interdisciplinary understanding of the Yalom's primary factors in the therapeutic process, such as: instillation of hope, corrective recapitulation of the primary family group, development of socializing techniques, imitative behavior, interpersonal learning, and group cohesion. Applied values of HAI are discussed for each factor, emphasizing the added value of animal presence in group therapy settings from the perspective of the dynamic of interspecific social networks, i.e., animal-handler-group members.

Integrative Model of Human-Animal Interactions: A One Health-One Welfare Systemic Approach to Studying HAI

The Integrative Model of Human-Animal Interactions (IMHAI) described herewith provides a conceptual framework for the study of interspecies interactions and aims to model the primary emotional processes involved in human-animal interactions. This model was developed from theoretical inputs from three fundamental disciplines for understanding interspecies interactions: neuroscience, psychology and ethology, with the objective of providing a transdisciplinary approach on which field professionals and researchers can build and collaborate. Seminal works in affective neuroscience offer a common basis between humans and animals and, as such, can be applied to the study of interspecies interactions from a One Health-One Welfare perspective. On the one hand, Jaak Panksepp's research revealed that primary/basic emotions originate in the deep subcortical regions of the brain and are shared by all mammals, including humans. On the other hand, several works in the field of neuroscience show that the basic physiological state is largely determined by the perception of safety. Thus, emotional expression reflects the state of an individual's permanent adaptation to ever-changing environmental demands. Based on this evidence and over 5 years of action research using grounded theory, alternating between research and practice, the IMHAI proposes a systemic approach to the study of primary-process emotional affects during interspecies social interactions, through the processes of emotional transfer, embodied communication and interactive emotional regulation. IMHAI aims to generate new hypotheses and predictions on affective behavior and interspecies communication. Application of such a model should promote risk prevention and the establishment of positive links between humans and animals thereby contributing to their respective wellbeing.

Collective Rhythm as an Emergent Property During Human Social Coordination

The literature on social interactions has shown that participants coordinate not only at the behavioral but also at the physiological and neural levels, and that this coordination gives a temporal structure to the individual and social dynamics. However, it has not been fully explored whether such temporal patterns emerge during interpersonal coordination beyond dyads, whether this phenomenon arises from complex cognitive mechanisms or from relatively simple rules of behavior, or which are the sociocultural processes that underlie this phenomenon. We review the evidence for the existence of group-level rhythmic patterns that result from social interactions and argue that the complexity of group dynamics can lead to temporal regularities that cannot be predicted from the individual periodicities: an emergent collective rhythm. Moreover, we use this interpretation of the literature to discuss how taking into account the sociocultural niche in which individuals develop can help explain the seemingly divergent results that have been reported on the social influences and consequences of interpersonal coordination. We make recommendations on further research to test these arguments and their relationship to the feeling of belonging and assimilation experienced during group dynamics.

Playing together, laughing together: rapid facial mimicry and social sensitivity in lowland gorillas

In nonhuman animals, the phenomenon of rapid facial mimicry (RFM)—the automatic, involuntary, and rapid (<1 s) replication of others’ facial expressions—has been mainly investigated in the playful domain. In immature lowland gorillas Gorilla gorilla gorilla both play face (PF) and full PF (FPF) are rapidly mimicked between the players. This makes the species suitable to test hypotheses on the factors influencing RFM during play. The observations on 3 captive groups of lowland gorillas (N = 27) revealed that contrary to expectations, the closeness of social bond negatively influenced the occurrence of RFM but it did not affect either RFM latency or its overlapping index (OVERLAP). RFM was affected by the degree of symmetry of play fighting: the more balanced the session, the higher the occurrence of RFM. Players of the same sex class responded faster than players of different sex. These findings suggest that RFM may help synchronizing behaviors of playmates matching in size (same-sex) and promote symmetric playful interactions. “Laughing together” (measured by the RFM OVERLAP) lasted longer when the responder perfectly mirrored the partner expression (PF→PF; FPF→FPF). If PF and FPF convey information on the different play roughness degree, through “laughing together” the players could coordinate their actions and share positive moods and playful intensity. If the perfect congruency in the motor resonance, also known as social sensitivity, can foster a possible emotional dialogue between gorillas remains to be investigated.

Visual communication in social play of a hierarchical carnivore species: the case of wild spotted hyenas

Communication relies on signals that can be produced via different sensory modalities to modify receivers’ behavior. During social interactions, the possibility to perceive subtle visual cues enhances the use of facial expressions to exchange information. One of the most appropriate fields to explore the specific design features of visual signals is play fighting. Here, we explored the production and potential role of Relaxed Open Mouth (ROM) and Head Bobbing (HB) in regulating play fighting of wild spotted hyenas Crocuta crocuta, a highly hierarchical carnivore species. In accordance with the assumptions of the signal optimization theory, wild hyenas produced ROM and HB almost exclusively when the sender was in direct visual contact with the receiver thus suggesting that senders were attentive to the playmates’ face. Contrary to HB, the sequential analysis revealed that ROM often anticipated offensive patterns such as play biting thus supporting the hypothesis that ROM, but not HB, is a metacomunicative signal. Moreover, when the offensive patterns were biased toward one of the 2 players, the session was punctuated by a higher number of ROMs. Our findings support the general hypothesis that these 2 visual signals can play different roles in the management of play fighting in this carnivore species. The complementary use of ROM and HB would suggest that spotted hyenas are highly competent and fast in processing facial displays of different nature to correctly “read others’ intentions” and respond with appropriate motor actions to avoid misunderstanding during one of the most multifaceted and risky social interaction.

Influence of workload and weather conditions on rolling behaviour of horses and mules

We evaluated the influences of workload intensity, bath handling and environmental conditions in the rolling behaviour of horses and mules. For this purpose, animals were observed after being exposed to different levels of workload and the rolling behaviour was recorded and described. During all testing procedures, the weather condition (temperature and humidity) was registered by a Black globe and Wet Bulb apparatus. Horses frequently rolled after intense exercise and after bath handling, independently of the weather condition. Mules frequently rolled after control (no exercise) and intense exercise in warmer and wetter days and after bath handlings in colder and drier days. Rolling behaviour characteristics were slightly different between species. While mules exhibited more frequently the behaviours of rest, self-care, yawn, tail swishing, complete spins, snort vocalization and use of the same spot to roll, horses exhibited more frequently the behaviours of paw, sniff, head and neck rubbing movements and incomplete spins to the right and left. This findings evidence that rolling is an important and frequently exhibited behaviour by domestic horses and mules, but animals may express it differently and may have their own motivations. In this sense, we believe that domestic equines, mainly those raised in more intensive livestock, should have the opportunities to freely express the rolling, as a way to improve their welfare conditions and with agreement with a more rational handling practice.

Let's unite in play! Play modality and group membership in wild geladas

Two of the main hypotheses put forth to explain the function of immature social play are the Social Skill Hypothesis and the Motor Training Hypothesis focussing on whether play can improve social competence to develop cooperative social networks or physical abilities to outcompete others, respectively. Here, we tested these hypotheses on a monkey species, the wild gelada (Theropithecus gelada) from the Kundi plateau, Ethiopia. This species is organized in bands divided in One-Male Units (OMUs), united only via social play. Immatures form 'play units' in which individuals from the same and different OMUs interact. We analysed the potential differences between inter- and intra-OMU play to verify which of the two hypotheses (Social Skill or Motor Training Hypothesis) best explains the function of play in geladas. We analysed 527 video-recorded social play sessions and found mixed support for both hypotheses. In agreement with the Social Skill Hypothesis, we found that play in geladas shows scarce social canalization being similarly distributed across age, sex and group membership. In line with the Motor Training Hypothesis, we detected higher levels of competition (shorter and more unbalanced sessions) in inter-OMU compared to intra-OMU play. Hence, in geladas play can be a tool for both the development of social relationships and the improvement of the physical skills necessary to cope with either future mates or competitors. In conclusion, neither hypothesis can be discarded and both hypotheses concur in explaining why immature geladas peculiarly form 'play units' embracing both ingroup and outgroup members.

Mirror replication of sexual facial expressions increases the success of sexual contacts in bonobos

Rapid Facial Mimicry (RFM), one of the possible predictors of emotional contagion, is defined as the rapid, involuntary and automatic replication of a facial expression. Up to now, RFM has been demonstrated in nonhuman animals exclusively during play. Since in bonobos, as in humans, socio-sexuality is a powerful tool for assessing/strengthening inter-individual relationships, we investigated RFM in this domain. Bonobos displayed silent bared-teeth (sbt, the most common facial expression during sexual contacts) more frequently after the detection of an sbt emitted by the trigger than in the no-detection condition. This is the first demonstration of the presence of RFM during sex. The occurrence of RFM was positively affected by the sex of the partners with female homo-sexual contacts being punctuated by a higher presence of RFM. At an immediate level, RFM increased the duration of homo- and hetero-sexual contacts. This finding suggests that RFM can increase individuals’ potential fitness benefits. By prolonging their sexual contacts, females can strengthen their social relationships thus increasing the probability to obtain priority over resources (RFM indirect fitness benefits). Via longer copulations, males can increase the probability to make females pregnant (RFM direct fitness benefits). In conclusion, in bonobos the access to the partner’s face during sexual contacts (face-to-face, proximate factor) and the role of socio-sexuality in increasing the individual direct and indirect fitness (ultimate factor) could have favoured the evolution of specific sexual facial expressions and their rapid mirror replication. Our findings on bonobos expand the role of RFM well beyond the animal play domain thus opening new scenarios for future comparative studies exploring the evolution of socio-sexuality in humans.