Contagious yawning, social cognition, and arousal: an investigation of the processes underlying shelter dogs’ responses to human yawns

Studies of contagious yawning have reported inconsistent findings regarding whether dogs exhibit this behavior and whether it is mediated by social-cognitive processes or the result of physiological arousal. We investigated why some dogs yawn in response to human yawns; particularly, whether these dogs are exceptional in their ability to understand human social cues or whether they were more physiologically aroused. Sixty shelter dogs were exposed to yawning and nonyawning control stimuli demonstrated by an unfamiliar human. We took salivary cortisol samples before and after testing to determine the role of arousal in yawn contagion. Dogs were tested on the object-choice task to assess their sensitivity for interpreting human social cues. We found that 12 dogs yawned only in response to human yawns (i.e., appeared to exhibit yawn contagion), though contagious yawning at the population level was not observed. Dogs that exhibited yawn contagion did not perform better on the object-choice task than other dogs, but their cortisol levels remained elevated after exposure to human yawning, whereas other dogs had reduced cortisol levels following yawning stimuli relative to their baseline levels. We interpret these findings as showing that human yawning, when presented in a stressful context, can further influence arousal in dogs, which then causes some to yawn. Although the precise social-cognitive mechanisms that underlie contagious yawning in dogs are still unclear, yawning between humans and dogs may involve some communicative function that is modulated by context and arousal.     

Contagious yawning in domestic dog puppies (Canis lupus familiaris): the effect of ontogeny and emotional closeness on low-level imitation in dogs

Contagious yawning is a well-documented phenomenon in humans and has recently attracted much attention from developmental and comparative sciences. The function, development and underlying mechanisms of the phenomenon, however, remain largely unclear. Contagious yawning has been demonstrated in dogs and several non-human primate species, and theoretically and empirically associated with empathy in humans and non-human primates. Evidence of emotional closeness modulating contagious yawning in dogs has, nonetheless, been contradictory. Humans show a developmental increase in susceptibility to yawn contagion, with typically developing children displaying a substantial increase at the age of four, when a number of cognitive abilities (e.g. accurate identification of others’ emotions) begin to clearly manifest. Explicit tests of yawn contagion in non-human animals have, however, thus far only involved adult individuals. Here, we report a study of the ontogeny of domestic dogs’ (Canis lupus familiaris) susceptibility to yawn contagion, and whether emotional closeness to the yawning model affects this. Thirty-five dogs, aged 4–14 months, observed a familiar and unfamiliar human repeatedly yawn or gape. The dogs yawned contagiously, but emotional closeness with the model did not affect the strength of contagion, raising questions as to recent evidence of emotionally modulated auditory contagious yawning in dogs. The dogs showed a developmental effect, with only dogs above 7 months evidencing contagion. The results support the notion of a developmental increase in dogs’ attention to others and identification of others’ emotional states and suggest that yawn contagion is underpinned by developmental processes shared by humans and other animals.     

No evidence for contagious yawning in lemurs

Among some haplorhine primates, including humans, relaxed yawns spread contagiously. Such contagious yawning has been linked to social bonds and empathy in some species. However, no studies have investigated contagious yawning in strepsirhines. We conducted an experimental study of contagious yawning in strepsirhines, testing ring-tailed and ruffed lemurs (n = 24) in a paradigm similar to one that has induced contagious yawning in haplorhines. First, in a control experiment, we investigated whether lemurs responded to projected video content in general (experiment 1). We showed them two videos to which we expected differential responses: one featured a terrestrial predator and the other a caretaker holding food. Next, to test for yawn contagion, we showed individual lemurs life-size video projections of groupmates and conspecific strangers yawning, and control footage of the same individuals at rest (experiment 2). Then, to examine whether a group context might enhance or allow for contagion, we exposed subjects to the same videos in a group setting (experiment 3). Lemurs produced alarm vocalizations and moved upward while viewing the predator, but not the caretaker, demonstrating that they do perceive video content meaningfully. However, lemurs did not yawn in response to yawning stimuli when tested alone, or with their groupmates. This study provides preliminary evidence that lemurs do not respond to yawning stimuli similarly to haplorhines, and suggests that this behavior may have evolved or become more exaggerated in haplorhines after the two major primate lineages split.     

Familiarity-connected or stress-based contagious yawning in domestic dogs (Canis familiaris)? Some additional data

The present short note aimed at further exploring data from a recent study showing socially modulated auditory contagious yawning in domestic dogs (Canis familiaris). Two independent observers further extended the analysis of all video recordings made in the previous study and coded both the number of yawns performed by the dogs and the frequencies or durations of stress-related behaviors exhibited throughout the presentation of familiar and unfamiliar yawns. By showing no significant difference between conditions in the frequencies or durations of the coded behaviors, nor any association between the number of yawns and the frequencies or durations of stress-related behaviors, results raised doubt on the stress-induced yawn hypothesis, thus supporting social modulation. The exact mechanism underlying contagious yawning, however, needs further research.     

Do dogs (Canis familiaris) show contagious yawning?

We report an experimental investigation into whether domesticated dogs display contagious yawning. Fifteen dogs were shown video clips of (1) humans and (2) dogs displaying yawns and open-mouth expressions (not yawns) to investigate whether dogs showed contagious yawning to either of these social stimuli. Only one dog performed significantly more yawns during or shortly after viewing yawning videos than to the open-mouth videos, and most of these yawns occurred to the human videos. No dogs showed significantly more yawning to the open-mouth videos (human or dog). The percentage of dogs showing contagious yawning was less than chimpanzees and humans showing this behavior, and considerably less than a recently published report investigating this behavior in dogs (Joly-Mascheroni et al. in Biol Lett 4:446–448, 2008).     

An investigation of auditory contagious yawning

Despite a widespread familiarity with the often compelling urge to yawn after perceiving someone else yawn, an understanding of the neural mechanism underlying contagious yawning remains incomplete. In the present auditory fMRI study, listeners used a 4-point scale to indicate how much they felt like yawning following the presentation of a yawn, breath, or scrambled yawn sound. Not only were yawn sounds given significantly higher ratings, a trait positively correlated with each individual’s empathy measure, but relative to control stimuli, random effects analyses revealed enhanced hemodynamic activity in the right posterior inferior frontal gyrus (pIFG) in response to hearing yawns. Moreover, pIFG activity was greatest for yawn stimuli associated with high as opposed to low yawn ratings and for control sounds associated with equally high yawn ratings. These results support a relationship between contagious yawning and empathy and provide evidence for pIFG involvement in contagious yawning. A supplemental figure for this study may be downloaded from http://cabn.psychonomic-journals.org/content/supplemental.     

Bridging a yawning chasm: EEG investigations into the debate concerning the role of the human mirror neuron system in contagious yawning

Ongoing debate in the literature concerns whether there is a link between contagious yawning and the human mirror neuron system (hMNS). One way of examining this issue is with the use of the electroencephalogram (EEG) to measure changes in mu activation during the observation of yawns. Mu oscillations are seen in the alpha bandwidth of the EEG (8–12 Hz) over sensorimotor areas. Previous work has shown that mu suppression is a useful index of hMNS activation and is sensitive to individual differences in empathy. In two experiments, we presented participants with videos of either people yawning or control stimuli. We found greater mu suppression for yawns than for controls over right motor and premotor areas, particularly for those scoring higher on traits of empathy. In a third experiment, auditory recordings of yawns were compared against electronically scrambled versions of the same yawns. We observed greater mu suppression for yawns than for the controls over right lateral premotor areas. Again, these findings were driven by those scoring highly on empathy. The results from these experiments support the notion that the hMNS is involved in contagious yawning, emphasise the link between contagious yawning and empathy, and stress the importance of good control stimuli.     

Contagious yawning and psychopathy

Psychopathy is characterized by a general antisocial lifestyle with behaviors including being selfish, manipulative, impulsive, fearless, callous, possibly domineering, and particularly lacking in empathy. Contagious yawning in our species has been strongly linked to empathy. We exposed 135 students, male and female, who completed the Psychopathic Personality Inventory-Revised (PPI-R), to a yawning paradigm intended to induce a reactionary yawn. Further, we exposed males to an emotion-related startle paradigm meant to assess peripheral amygdalar reactivity. We found that scores on the PPI-R subscale Coldheartedness significantly predicted a reduced chance of yawning. Further, we found that emotion-related startle amplitudes were predictive of frequency of contagious yawning. These data suggest that psychopathic traits may be related to the empathic nature of contagious yawning in our species.     

Yawning frequency and distribution in preterm and near term infants assessed throughout 24-h recordings

Yawning has been observed in foetuses and preterm infants. The aim of this study was to assess the frequency and the 24 h distribution of yawning in preterm infants.Twelve low-risk infants between 31 and 40 weeks of post-conceptional age (PCA) were continuously video-recorded for 24 h in their incubator. Spontaneous yawning was defined as opening of the mouth to its full extension in a dramatic stretch movement.The results showed that the rate of yawning across the 24-h period was 1.10/h. The highest incidence of yawns was in the waking motility pattern when compared to active sleep or quiet sleep motility patterns.Between 31 and 40 weeks, yawn incidence significantly decreased mainly during the day. The marked decrease in yawn frequency with age may be related to the development of circadian and homeostatic control of sleep and wake.     

哈欠传染的发展与演化：一项探索性研究

传染性哈欠可能承载着一定的社会功能,但实证证据还非常有限。研究收集了大学生和老年人两个年龄群体的传染性哈欠和自发性哈欠数据,测量了抑制控制和观点采择,同时采用问卷测查参与者睡眠状况等。结果发现：大学生表现出哈欠传染,但这种现象在老年人群体中不明显;传染性哈欠和个体的抑制控制能力存在共变关系;相比传染性哈欠,自发性哈欠更多与一些基本的生理因素（如睡眠状况、警觉程度）相关。结果为从种系发生和个体发生两个层面探究传染性哈欠的机制提供了基础数据。     

Auditory disturbances promote temporal clustering of yawning and stretching in small groups of budgerigars (Melopsittacus undulatus)

Yawning may serve both social and nonsocial functions. When budgerigars (Melopsittacus undulatus) are briefly held, simulating capture by a predator, the temporal pattern of yawning changes. When this species is observed in a naturalistic setting (undisturbed flock), yawning and also stretching, a related behavior, are mildly contagious. On the basis of these findings, we hypothesized that a stressful event would be followed by the clustering of these behaviors in a group of birds, which may be facilitated both by a standard pattern of responding to a startling stressor and also contagion. In this study, we measured yawning and stretching in 4-bird groups following a nonspecific stressor (loud white noise) for a period of 1 hr, determining whether auditory disturbances alter the timing and frequency of these behaviors. Our results show that stretching, and to a lesser degree yawning, were nonrandomly clumped in time following the auditory disturbances, indicating that the temporal clustering is sensitive to, and enhanced by, environmental stressors while in small groups. No decrease in yawning such as found after handling stress was observed immediately after the loud noise but a similar increase in yawning 20 min after was observed. Future research is required to tease apart the roles of behavioral contagion and a time-setting effect following a startle in this species. This research is of interest because of the potential role that temporal clumping of yawning and stretching could play in both the collective detection of, and response to, local disturbances or predation threats.     

Children's understanding of the transmission of genetic disorders and contagious illnesses

The authors conducted 4 studies suggesting that children attribute different modes of transmission to genetic disorders and contagious illnesses. Study 1 presented preschoolers through 5th graders and adults with "switched-at-birth" scenarios for various disorders. Study 2 presented preschoolers with the same disorders but used contagion links in a contagion context. Studies 3 and 4 presented preschoolers and adults with novel (fictitious) illnesses to determine which cues participants would use to differentiate the modes of transmission. In the presence of kinship cues, children distinguished genetic disorders from contagious illnesses, but in the presence of contagion cues, preschoolers selectively applied contagious links primarily to contagious illnesses. With novel illnesses, preschoolers and adults inferred that permanent illnesses were more likely to be transmitted by birth parents than by contagion. These results suggest that by the preschool years, children recognize that not all disorders are transmitted exclusively through germ contagion.     

Self-monitoring and mimicry of positive and negative social behaviors

This study examined the role that self-monitoring plays in behavioral mimicry. Participants were exposed to videotaped targets who were laughing, yawning, frowning, or neutral in their expression. Participants’ behavioral mimicry while viewing the targets was recorded. It was hypothesized that higher self-monitors would show greater mimicry than lower self-monitors. It was also hypothesized that participants would respond differently to positive and negative target expressions. Participants who scored higher in self-monitoring did mimic the targets’ behaviors more often, and participants showed less mimicry of frowns than of laughs or yawns.     

Mass Killings in the United States from 2006 to 2013: Social Contagion or Random Clusters?

In line with previous research on suicide and social contagion, there has been widespread speculation that mass killings—which often involve suicidal offenders—are socially contagious for up to 14 days. This study tested these claims by making comparisons (i) between observed chronological clusters of mass killings in the United States from 2006 to 2013 and clusters in 500 simulations containing 116,000 randomly generated dates, and then (ii) between observed mass killings receiving varying levels of public attention. No evidence of short‐term contagion was found, although longer term copycat effects may exist. Further scholarly and policy implications are discussed.     

Seeing others yawn selectively enhances vigilance: an eye-tracking study of snake detection

Animal Cognition - While the origin of yawning appears to be physiologic, yawns may also hold a derived communicative function in social species. In particular, the arousal reduction...     

Investigating emotional contagion in dogs (<Emphasis Type="Italic">Canis familiaris</Emphasis>) to emotional sounds of humans and conspecifics

Emotional contagion, a basic component of empathy defined as emotional state-matching between individuals, has previously been shown in dogs even upon solely hearing negative emotional sounds of humans or conspecifics. The current investigation further sheds light on this phenomenon by directly contrasting emotional sounds of both species (humans and dogs) as well as opposed valences (positive and negative) to gain insights into intra- and interspecies empathy as well as differences between positively and negatively valenced sounds. Different types of sounds were played back to measure the influence of three dimensions on the dogs’ behavioural response. We found that dogs behaved differently after hearing non-emotional sounds of their environment compared to emotional sounds of humans and conspecifics (“Emotionality” dimension), but the subjects responded similarly to human and conspecific sounds (“Species” dimension). However, dogs expressed more freezing behaviour after conspecific sounds, independent of the valence. Comparing positively with negatively valenced sounds of both species (“Valence” dimension), we found that, independent of the species from which the sound originated, dogs expressed more behavioural indicators for arousal and negatively valenced states after hearing negative emotional sounds. This response pattern indicates emotional state-matching or emotional contagion for negative sounds of humans and conspecifics. It furthermore indicates that dogs recognized the different valences of the emotional sounds, which is a promising finding for future studies on empathy for positive emotional states in dogs.     

Is yawning an arousal defense reflex?

Despite the fact that yawning is a reality of everyday life, its study is not included in the curriculum of medical schools, and most medical textbooks barely mention its existence. Two factors may help to explain this puzzling situation: (a) yawning's borderline position between psychology and neurology, and (b) researchers' lack of understanding as to why people yawn. After review of the literature and personal observation, it is concluded that yawning is a complex arousal defense reflex located in the reticular brainstem with a peripheral and central arche, whose aim is to reverse brain hypoxia. Yawning occurs with loss of interest (boredom) and may or may not be associated with fatigue. By reversing drowsiness, yawning avoids a decreased concentration capacity resulting from borderline hypoxia. It is hoped that this article will stimulate further research on the phenomenon.     

Empathic-like responding by domestic dogs (Canis familiaris) to distress in humans: an exploratory study

Empathy covers a range of phenomena from cognitive empathy involving metarepresentation to emotional contagion stemming from automatically triggered reflexes. An experimental protocol first used with human infants was adapted to investigate empathy in domestic dogs. Dogs oriented toward their owner or a stranger more often when the person was pretending to cry than when they were talking or humming. Observers, unaware of experimental hypotheses and the condition under which dogs were responding, more often categorized dogs' approaches as submissive as opposed to alert, playful or calm during the crying condition. When the stranger pretended to cry, rather than approaching their usual source of comfort, their owner, dogs sniffed, nuzzled and licked the stranger instead. The dogs' pattern of response was behaviorally consistent with an expression of empathic concern, but is most parsimoniously interpreted as emotional contagion coupled with a previous learning history in which they have been rewarded for approaching distressed human companions.     

Sympathetic action in the seventeenth century: human and natural

The category of sympathy marks a number of basic divisions in early modern approaches to action explanations, whether for human agency or for change in the wider natural world. Some authors were critical of using sympathy to explain change. They call such principles “unintelligible” or assume they involve “mysterious” action at a distance. Others, including Margaret Cavendish, Anne Conway, and Gottfried Wilhelm Leibniz, appeal to sympathy to capture natural phenomena (yawn contagion, magnetism), or to supply a backbone to their metaphysics. Here I discuss how concerns about sympathetic actions form at least a partial background for differing seventeenth-century conceptions of what it is to explain action. I argue that critics of sympathy generally insist on an “atomistic” approach to action explanation, which makes primitively relational phenomena come out as problematic. Proponents of sympathy, by contrast, allow for a more holistic approach to action explanation, which allows for such basic connections. Hence, divergent attitudes toward sympathetic action in part explain differences in approaches to explanation. I conclude by showing how some of these core concerns fade into the background when in the eighteenth-century sympathy gets psychologised and individualised.     

Gaze-following behind barriers in domestic dogs

Although gaze-following abilities have been demonstrated in a wide range of species, so far no clear evidence has been available for dogs. In the current study, we examined whether dogs follow human gaze behind an opaque barrier in two different contexts, in a foraging situation and in a non-foraging situation (food involved vs. food not involved in the situation). We assumed that dogs will spontaneously follow the human gaze and that the foraging context will have a positive effect on dogs’ gaze-following behaviour by causing an expectation in the dogs that food might be hidden somewhere in the room and might be communicated by the experimenter. This expectation presumably positively affects their motivational and attentional state. Here, we report that dogs show evidence of spontaneous gaze-following behind barriers in both situations. According to our findings, the dogs gazed earlier at the barrier in the indicated direction in both contexts. However, as we expected, the context also has some effect on dogs’ gaze-following behaviour, as more dogs gazed behind the barrier in the indicated direction in the foraging situation. The present results also support the idea that gaze-following is a characteristic skill in mammals which may more easily emerge in certain functional contexts.