Evolution of emotional contagion in group-living animals

Cheerful tails: Delving into positive emotional contagion

This review delves into the phenomenon of positive emotional contagion (PEC) in rodents, an area that remains relatively understudied compared to the well-explored realm of negative emotions such as fear or pain. Rodents exhibit clear preferences for individuals expressing positive emotions over neutral counterparts, underscoring the importance of detecting and responding to positive emotional signals from others. We thoroughly examine the adaptive function of PEC, highlighting its pivotal role in social learning and environmental adaptation. The developmental aspect of the ability to interpret positive emotions is explored, intricately linked to maternal care and social interactions, with oxytocin playing a central role in these processes. We discuss the potential involvement of the reward system and draw attention to persisting gaps in our understanding of the neural mechanisms governing PEC. Presenting a comprehensive overview of the existing literature, we focus on food-related protocols such as the Social Transmission of Food Preferences paradigm and tickling behaviour. Our review emphasizes the pressing need for further research to address lingering questions and advance our comprehension of positive emotional contagion.

Preliminary Behavioural Observations of Horseback Safaris: Initial Insights into the Welfare Implications for Horses and Herbivorous Plains Game Species

In Africa, wildlife-watching experiences create substantial revenue from tourists that can finance wildlife conservation. Horseback safaris, where an experienced guide takes guests through the bush on horseback to observe plains game species, are a popular activity. Close encounters between ridden horses and game species are unnatural and potentially stressful situations, and horseback safaris may have adverse impacts on both the horses and the wildlife they have come to observe. This study aims to provide a preliminary insight into the behavioural responses of horses and herbivorous plains game species, including giraffe, zebra and impala, as a proxy measure of the potential welfare implications of horseback safaris. Seventeen group safari rides were observed encompassing 72 encounters with plains game species. Game species differed in their response to encounters with the horseback safari ride. Equine response behaviour appeared to be influenced by the species of game encountered. Horses seemed more wary of giraffe than other species, with a higher percentage of horses showing stationary and retreat behaviour at the start of giraffe encounters. They were also most likely to shy at giraffe. The behavioural responses suggest that game encounters can elicit a stress response in both animal groups, although it is not usually extreme, potentially indicating that some degree of habituation has occurred. Balancing the welfare of both the horses and the plains game species along with tourist preferences may be challenging in this context.

Light makeup decreases receivers' negative emotional experience

Makeup is widely used in modern society and has a positive effect on perceived attractiveness. However, little is known about the other possible outcomes of makeup use. In this study, we investigated whether makeup enhances a receiver's emotional experience. Dynamic faces with or without makeup are presented in Experiments 1 and 2. Participants were asked to imagine themselves video chatting with a target person (expresser) with different expressions: neutral, angry, sad, or happy, and then to appraise their own subjective emotional experience. Emotional valence, arousal, and willingness to communicate were also assessed in Experiment 2. The results showed that makeup improved perceived facial attractiveness and increased the willingness to communicate. More importantly, it revealed that wearing makeup could weaken receivers' negative experiences arising from the angry and sad conditions, which is not the case for the non-makeup condition, but could not affect the happy contagion. Furthermore, incremental changes in the amount of makeup were not accompanied by incremental changes in emotional appraisal (valence and arousal). Overall, we found that makeup may affect emotional contagion and interpersonal communication. Whether the alleviated negative experience due to makeup is adaptive may need further discussion.

Watching others in a positive state does not induce optimism bias in common marmosets (Callithrix jacchus), but leads to behaviour indicative of competition

Emotional contagion is suggested to facilitate group life by enhancing synchronized responses to the environment. Cooperative breeders are an example of a social system that requires such intricate coordination between individuals. Therefore, we studied emotional contagion in common marmosets by means of a judgement bias test. Demonstrators were exposed to an emotion manipulation (i.e., positive, negative, control), and observers perceived only the demonstrator's behaviour. We predicted that the positive or negative states of the demonstrator would induce matching states in the observer, indicating emotional contagion. All subjects' emotional states were assessed through behaviour and cognition, the latter by means of a judgement bias test. Behavioural results showed a successful emotion manipulation of demonstrators, with manipulation-congruent expressions (i.e., positive calls in the positive condition, and negative calls and pilo-erect tail in the negative condition). Observers showed no manipulation-congruent expressions, but showed more scratching and arousal after the positive manipulation. Concerning the judgement bias test, we predicted that subjects in a positive state should increase their response to ambiguous cues (i.e., optimism bias), and subjects in a negative state should decrease their response (i.e., pessimism bias). This prediction was not supported as neither demonstrators nor observers showed such bias in either manipulation. Yet, demonstrators showed an increased response to the near-positive cue, and additional analyses showed unexpected responses to the reference cues, as well as a researcher identity effect. We discuss all results combined, including recently raised validation concerns of the judgement bias test, and inherent challenges to empirically studying emotional contagion.

Game dynamics of emotion evolution based on the Moran process

In this paper, emotions are classified into four types, namely, respect for the strong, envying the strong, sympathy for the weak, and bullying the weak. The corresponding relationship between the four emotion types and the two behaviors of competition and cooperation is then defined. The payoff matrices of the game based on emotions are obtained and the evolutionary dynamics of the four emotion types in a finite population based on the Moran process are studied. Next, we derive the absorption probabilities of a 4×4 symmetric evolutionary game of the population. The influence of the payoff parameters and the natural selection intensity on the result of the group evolution are then analyzed. The calculations indicate that there are differences in the absorption probabilities of the four absorption states of the system. At a steady state, individuals of the types envying the strong and bullying the weak have the highest probability of occupying the entire population, and individuals of the type respect for the strong and sympathy for the weak have the lowest one. By comparing the level of cooperation and average payoffs at a steady state, we observe that the level of cooperation and average payoffs based on the proposed model are better than those of the prisoner's dilemma game with two behaviors. Therefore, emotional evolution can promote cooperation and achieve better group fitness.

Where Do We Stand in the Domestic Dog ( Canis familiaris ) Positive-Emotion Assessment: A State-of-the-Art Review and Future Directions

Although there have been a growing number of studies focusing on dog welfare, the research field concerning dog positive-emotion assessment remains mostly unexplored. This paper aims to provide a state-of-the-art review and summary of the scattered and disperse research on dog positive-emotion assessment. The review notably details the current advancement in dog positive-emotion research, what approaches, measures, methods, and techniques have been implemented so far in emotion perception, processing, and response assessment. Moreover, we propose possible future research directions for short-term emotion as well as longer-term emotional states assessment in dogs. The review ends by identifying and addressing some methodological limitations and by pointing out further methodological research needs.

Emotional Contagion From Humans to Dogs Is Facilitated by Duration of Ownership

Emotional contagion is a primitive form of empathy that does not need higher psychological functions. Recent studies reported that emotional contagion exists not only between humans but also among various animal species. The dog (Canis familiaris) is a unique animal and the oldest domesticated species. Dogs have coexisted with humans for more than 30,000 years and are woven into human society as partners bonding with humans. Dogs have acquired human-like communication skills and, likely as a result of the domestication process, the ability to read human emotions; therefore, it is feasible that there may be emotional contagion between human and dogs. However, the higher time-resolution of measurement of emotional contagion between them is yet to be conducted. We assessed the emotional reactions of dogs and humans by heart rate variability (HRV), which reflects emotion, under a psychological stress condition on the owners. The correlation coefficients of heart beat (R-R) intervals (RRI), the standard deviations of all RR intervals (SDNN), and the square root of the mean of the sum of the square of differences between adjacent RR intervals (RMSSD) between dogs and owners were positively correlated with the duration of dog ownership. Dogs’ sex also influenced the correlation coefficients of the RRI, SDNN, and RMSSD in the control condition; female showed stronger values. These results suggest that emotional contagion from owner to dog can occur especially in females and the time sharing the same environment is the key factor in inducing the efficacy of emotional contagion.

Vegetative symptoms and behaviour of the therapy-accompanying dog of a chronically suicidal patient

We herein present a 51-year-old single female inpatient with treatment-resistant recurrent depressive disorder. Her most recent depressive episode has been severe and followed a chronic course, lasting for longer than 2 years. During the exacerbation of the patient's suicidal thoughts and plans, we repeatedly and independently observed vegetative and behavioural changes of the therapy-accompanying dog of the patient. Our findings suggest a role for dog-assisted therapy for augmenting treatment as well as for enhancing and developing novel adjunctive strategies for risk assessment in patients with chronic depression and suicidality. Possible social-biological mechanisms and underpinnings are discussed, by drawing on the available literature and comparative psychology. Collaboration with animal behaviourists and animal welfare scientists, in order to improve behavioural and physiological data interpretation and humaneness of dog-assisted therapy, is emphasised as a crucial component of future research.