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Prosocial behaviors (i.e., actions that benefit others) are central for social interactions in humans and other animals, by fostering social bonding and cohesion. To study prosociality in rodents, scientists have developed behavioral paradigms where animals can display actions that benefit conspecifics in distress or need. These paradigms have provided insights into the role of social interactions and transfer of emotional states in the expression of prosociality, and increased knowledge of its neural bases. However, prosociality levels are variable: not all tested animals are prosocial. Such variation has been linked to differences in animals' ability to process another's state as well as to contextual factors. Moreover, evidence suggests that prosocial behaviors involve the orchestrated activity of multiple brain regions and neuromodulators. This review aims to synthesize findings across paradigms both at the level of behavior and neural mechanisms. Growing evidence confirms that these processes can be studied in rodents, and intense research in the past years is rapidly advancing our knowledge. We discuss a strong bias in the field towards the study of these processes in negative valence contexts (e.g., pain, fear, stress), which should be taken as an opportunity to open new venues for future research. [ABSTRACT FROM AUTHOR]

In this review, we consider the definitions and experimental approaches to emotional contagion and prosocial behaviour in mammals and explore their evolutionary conceptualisation for studying their occurrence in the evolutionarily divergent vertebrate group of ray-finned fish. We present evidence for a diverse set of fish phenotypes that meet definitional criteria for prosocial behaviour and emotional contagion and discuss conserved mechanisms that may account for some preserved social capacities in fish. Finally, we provide some considerations on how to address the question of interdependency between emotional contagion and prosocial response, highlighting the importance of recognition processes, decision-making systems, and ecological context for providing evolutionary explanations. • Emotional contagion can explain ancestral forms of prosocial behaviour in fish. • The testable basis is state transfer triggering appropriate benefit from others' acts. • Recognition processes are a paramount component to elucidating this link. • Comparative approaches can reveal evolutionary substrates for higher-order functions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Social learning is one of the most efficient strategies for adapting to the dynamically changing environment • Various forms of learning from others manifest themselves across different taxa of increasing biological complexity • The emotional states of others evoked by interactions with the environment are an essential ingredient of social information • Two critical factors impacting social learning are the pertinence of information for survival and the type of relationship. The natural habitats of most species are far from static, forcing animals to adapt to continuously changing conditions. Perhaps the most efficient strategy addressing this challenge consists of obtaining and acting upon pertinent information from others through social learning. We discuss how animals transfer information via social channels and what are the benefits of such exchanges, playing out on different levels, from theperception of socially delivered information to emotional sharing, manifesting themselves across different taxa of increasing biological complexity. We also discuss how social learning is influenced by different factors including pertinence of information for survival, the complexity of the environment, sex, genetic relatedness, and most notably, the relationship between interacting partners. The results appear to form a consistent picture once we shift our focus from emotional contagion as a prerequisite for empathy onto the role of shared emotions in providing vital information about the environment. From this point of view, we can propose approaches that are the most promising for further investigation of complex social phenomena, including learning from others. [ABSTRACT FROM AUTHOR]

• Rats and mice show comparable levels of emotional contagion. • Rats and mice show an equivalent contagion response to familiar and unfamiliar conspecifics. • Prior experience with an emotional stimulus increases fear contagion response in rats but not in mice. • Social testing condition influences the level of contagion. Here we leverage 80 years of emotional contagion research in rodents and perform the first meta-analysis on this topic. Using 457 effect sizes, we show that, while both rats and mice are capable of emotional contagion, there are differences in how various factors modulate empathy in these species: 1) only mice show strain-specific differences in emotional contagion response; 2) although rats and mice have equivalent contagion response to familiar and unfamiliar individuals, our results show that familiarity length is negatively correlated with level of contagion in rats only; 3) prior experience with emotional stimuli almost doubles fear contagion response in rats while no changes are detected in pre-exposed mice; 4) both mice and rats tested alone show comparable reduced contagion compared to animals tested in a group; 5) emotional contagion is reduced in animals from both species missing one sensory modality compared to situations where all sensory modalities are recruited during emotional contagion. Lastly, we report similar patterns of brain activation during emotional contagion in rats and mice. [ABSTRACT FROM AUTHOR]

• Recognising conspecifics' emotional expressions is a fundamental skill for primates. • Emotional contagion and cognitive empathy underlie emotion recognition. • New techniques facilitate the experimental study of emotion processing. • A wide range of primates can infer emotional meaning from emotional expressions. • More comparative research in different modalities and species is necessary. Recognising conspecifics' emotional expressions is important for nonhuman primates to navigate their physical and social environment. We address two possible mechanisms underlying emotion recognition: emotional contagion , the automatic matching of the observer's emotions to the emotional state of the observed individual, and cognitive empathy , the ability to understand the meaning and cause of emotional expressions while maintaining a distinction between own and others' emotions. We review experimental research in nonhuman primates to gain insight into the evolution of emotion recognition. Importantly, we focus on how emotional contagion and cognitive empathy can be studied experimentally. Evidence for aspects of cognitive empathy in different nonhuman primate lineages suggests that a wider range of primates than commonly assumed can infer emotional meaning from emotional expressions. Possibly, analogous rather than homologous evolution underlies emotion recognition. However, conclusions regarding its exact evolutionary course require more research in different modalities and species. [ABSTRACT FROM AUTHOR]

• Literature on comparative empathy and related phenomena is critically reviewed • Theoretical models should distinguish between distinct empathy related phenomena • Empirical findings are more ambiguous than previously presented • The emotional basis of these phenomena needs greater attention, particularly valence • A multi-component model captures this emotional basis beyond behavior alone The aim of this review is to discuss recent arguments and findings in the comparative study of empathy. Based on a multidisciplinary approach including psychology and ethology, we review the non-human animal literature concerning theoretical frameworks, methodology, and research outcomes. One specific objective is to highlight discrepancies between theory and empirical findings, and to discuss ambiguities present in current data and their interpretation. In particular, we focus on emotional contagion and its experimental investigation, and on consolation and targeted helping as measures for sympathy. Additionally, we address the feasibility of comparing across species with behavioural data alone. One main conclusion of our review is that animal research on empathy still faces the challenge of closing the gap between theoretical concepts and empirical evidence. To advance our knowledge, we propose to focus more on the emotional basis of empathy, rather than on possibly ambiguous behavioural indicators, and we provide suggestions to overcome the limitations of previous research. [ABSTRACT FROM AUTHOR]

• Stressful experiences can be transmitted among individuals through social interactions. • Rodent studies of vicarious social defeat stress and social defeat stress crossover are reviewed. • The vicarious experience of social defeat is associated with a host of physiological and behavioral deficits. • Social interaction with a stressed partner in the aftermath of social defeat elicits stress responses. • These models can be useful for studying the neurobiological processes underlying the contagion of stress across individuals. Stressful experiences can be transmitted among individuals through social interactions. Like humans, rodents are social creatures whose behavior and physiology can be influenced by the emotional state of fellow rodents. This paper will review rodent studies which have explored two conditions of potential social stress contagion using the social defeat paradigm. In the vicarious social defeat model, mice and rats that witness a conspecific being socially defeated exhibit physiological stress responses and develop a host of depressive- and anxiety-like behavioral deficits. Likewise, social interaction with a stressed partner in the aftermath of social defeat stress results in physiological stress responses and social avoidance behavior. After summarizing the existing literature on this newly emerging area of social defeat stress contagion in rodents, we will discuss the potential utility of these rodent models for investigating the neurobiological processes and sensory channels of information that allow for the spread of psychophysiological effects of stress across individuals. [ABSTRACT FROM AUTHOR]

• Yawn contagion and play face mimicry are found in human and non-human animals. • In humans facial muscle contraction has a causal effect on brain emotion generation. • Mimicry phenomena highlight a correlative link between bodily and emotional states. • This link, found in animals, may be evolutionarily more ancient than expected. • A shared approach is proposed for research on human and non-human animals. Spontaneous mimicry appears fundamental to emotional perception and contagion, especially when it involves facial emotional expressions. Here we cover recent evidence on spontaneous mimicry from ethology, psychology and neuroscience, in non-human and human animals. We first consider how mimicry unfolds in non-human animals (particularly primates) and how it relates to emotional contagion. We focus on two forms of mimicry-related phenomena: facial mimicry and yawn contagion, which are largely conserved across mammals and useful to draw evolutionary scenarios. Next, we expand on the psychological evidence from humans that bears on current theoretical debates and also informs non-human animal research. Finally, we cover the neural bases of facial mimicry and yawn contagion. We move beyond the perception/expression/experience trichotomy and from the correlational to the causal evidence that links facial mimicry to emotional contagion by presenting evidence from neuroimaging, direct manipulation, neuro-stimulation and lesion studies. In conclusion, this review proposes a bottom-up, multidisciplinary approach to the study of spontaneous mimicry that accounts for the evolutionary continuity linking non-human and human animals. [ABSTRACT FROM AUTHOR]

Highlights • Empathy is a cornerstone of healthcare, social justice, and international relations. • Empathy depends on automatic (Empathy1) and controlled (Empathy2) mechanisms. • The automatic mechanism, Empathy1, is constructed by associative learning. • Self-stimulation, synchronous emotion and affect mirroring provide inputs to learning. • Empathy can be enhanced by novel experience and broken by social change. Abstract In academic and public life empathy is seen as a fundamental force of morality – a psychological phenomenon, rooted in biology, with profound effects in law, policy, and international relations. But the roots of empathy are not as firm as we like to think. The matching mechanism that distinguishes empathy from compassion, envy, schadenfreude, and sadism is a product of learning. Here I present a dual system model that distinguishes Empathy1, an automatic process that catches the feelings of others, from Empathy2, controlled processes that interpret those feelings. Research with animals, infants, adults and robots suggests that the mechanism of Empathy1, emotional contagion, is constructed in the course of development through social interaction. Learned Matching implies that empathy is both agile and fragile. It can be enhanced and redirected by novel experience, and broken by social change. [ABSTRACT FROM AUTHOR]

The heterogeneity of the literature on empathy highlights its multidimensional and dynamic nature and affects unclear descriptions of empathy in the context of psychopathology. The Zipper Model of Empathy integrates current theories of empathy and proposes that empathy maturity is dependent on whether contextual and personal factors push affective and cognitive processes together or apart. This concept paper therefore proposes a comprehensive battery of physiological and behavioral measures to empirically assess empathy processing according to this model with an application for psychopathic personality. We propose using the following measures to assess each component of this model: (1) facial electromyography; (2) the Emotion Recognition Task; (3) the Empathy Accuracy task and physiological measures (e.g., heart rate); (4) a selection of Theory of Mind tasks and an adapted Dot Perspective Task, and; (5) an adjusted Charity Task. Ultimately, we hope this paper serves as a starting point for discussion and debate on defining and assessing empathy processing, to encourage research to falsify and update this model to improve our understanding of empathy. • The Zipper Model of Empathy details how cognitive and affective processes of empathy interact bi-directionally to achieve mature empathy (empathic behavior). • An empirical neuroclinical assessment of the Zipper model is proposed, consisting of a battery of validated clinical tasks. • Predicted outcomes of these measures with certain psychopathologies in mind, notably with psychopathic personality, but also autism spectrum disorder, and alexithymia. • Initiate discussion, debate, and falsification of empathy constructs by empirically testing and validating neuroclinical assessments. [ABSTRACT FROM AUTHOR]

Various studies and researchers have proposed a link between contagious yawning and empathy, yet the conceptual basis for the proposed connection is not clear and deserves critical evaluation. Therefore, we systematically examined the available empirical evidence addressing this association; i.e., a critical review of studies on inter-individual differences in contagion and self-reported values of empathy, differences in contagion based on familiarity or sex, and differences in contagion among individuals with psychological disorders, as well as developmental research, and brain imaging and neurophysiological studies. In doing so, we reveal a pattern of inconsistent and inconclusive evidence regarding the connection between contagious yawning and empathy. Furthermore, we identify study limitations and confounding variables, such as visual attention and social inhibition. Future research examining links between contagious yawning and empathy requires more rigorous investigation involving objective measurements to explicitly test for this connection. [ABSTRACT FROM AUTHOR]

During social interactions, people tend to automatically align with, or mimic their interactor’s facial expressions, vocalizations, postures and other bodily states. Automatic mimicry might be implicated in empathy and affiliation and is impaired in several pathologies. Despite a growing body of literature on its phenomenology, the function and underlying mechanisms of mimicry remain poorly understood. The current review puts forward a new Neurocognitive Model of Emotional Contagion (NMEC), demonstrating how basic automatic mimicry can give rise to emotional contagion. We combine neurological, developmental and evolutionary insights to argue that automatic mimicry is a precursor to healthy social development. We show that (i) strong synchronization exists between people, (ii) that this resonates on different levels of processing and (iii) demonstrate how mimicry translates into emotional contagion. We conclude that our synthesized model, built upon integrative knowledge from various fields, provides a promising avenue for future research investigating the role of mimicry in human mental health and social development. [ABSTRACT FROM AUTHOR]

Empathy is a phenomenon often considered dependent on higher-order emotional control and an ability to relate to the emotional state of others. It is, by many, attributed only to species having well-developed cortical circuits capable of performing such complex tasks. However, over the years, a wealth of data has been accumulated showing that rodents are capable not only of sharing emotional states of their conspecifics, but also of prosocial behavior driven by such shared experiences. The study of rodent empathic behaviors is only now becoming an independent research field. Relevant animal models allow precise manipulation of neural networks, thereby offering insight into the foundations of empathy in the mammalian brains. Here we review the data on empathic behaviors in rat and mouse models, their neurobiological and neurophysiological correlates, and the factors influencing these behaviors. We discuss how simple rodent models of empathy enhance our understanding of how brain controls empathic behaviors. [ABSTRACT FROM AUTHOR]

Social interaction can have a profound effect on individual behavior, perhaps most salient in interactions between sick suffering children and their parents. Chronic pain is a difficult condition that can produce considerable changes in children’s behaviors that can secondarily have profound effects on their parents. It may create a functionally disabling negative feedback loop. Research supports the notion of alterations in the brain of individuals who observe and empathize with loved ones in acute pain. However, neural activity in relation to empathic responses in the context of chronic pain has not been examined. Ongoing suffering with chronic pain in a child can result in child’s brain circuit alterations. Moreover, prolonged suffering jointly experienced by the parent may putatively produce maladaptive changes in their neural networks and consequently in parental behaviors. Here we put forth the conceptual framework for ‘ Chronic pain contagion ’ (CPC). We review the underlying processes in CPC and discuss implications for devising and implementing treatments for children in chronic pain and their parents. [ABSTRACT FROM AUTHOR]

Despite increasing empirical and theoretical work on empathy, particularly on the content of empathic representations, there is a relative lack of consensus regarding the information processing necessary for empathy to occur. Here we attempt to delineate a mechanistic cognitive model of empathy in order to provide a framework within which neuroimaging work on empathy can be located, and which may be used in order to understand various disorders characterised by atypical levels of empathy. To this end data from individuals with psychopathy, autism, and alexithymia inform the model, and the model is used to provide a unifying framework for any empathy impairments seen in these disorders. The model adopts a developmental framework and tries to address the four difficult questions of empathy: How do we know what another is feeling? What is the role of theory of mind in empathy? How does the state of another cause a corresponding state in the self? How do we represent another's emotion once emotional contagion has taken place? [ABSTRACT FROM AUTHOR]

• Contagious depression is a real phenomenon possible due to emotional contagion. • Automatic mimicry is a preserved behavior that allows emotional synchrony. • The Mirror Neuron System is a key component for empathy processing. • Depressed patients have a flawed pattern of brain activation in mirror neuron areas. • Contagious depression is related to environmental and intrinsic factors combined. Contagious depression is a theory proposing that depression can be induced or triggered by our social environment. This theory is based on emotional contagion, the idea that affective states can be transferred during social interaction, since humans can use emotional contagion to communicate feelings and emotions in conscious and unconscious ways. This review presents behavioral, physiological, and neuroanatomical aspects of two essential contagious depression mechanisms, automatic mimicry and the mirror neuron system. [ABSTRACT FROM AUTHOR]

Palagi et al. (Neurosci. Biobehav. Rev. 111:149-165, 2020) propose a multidisciplinary approach to the study of spontaneous mimicry, focusing on comparative research on facial mimicry and contagious yawning. In doing so, the authors highlight connections between these behaviors and emotional contagion. The aim of this commentary is to critically evaluate the link between contagious yawning and emotional contagion, address the role of attention in contagious yawning, and promote further research examining the sensory and perceptual factors driving variability in contagious yawning. Contrary to the position of Palagi et al., a strong matching between emotional contagion and contagious yawning has not been established. Variation in contagious yawning appears to be driven by biased attentional processes and yawn detection rather than emotional sharing. [ABSTRACT FROM AUTHOR]