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Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
 
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal
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 mystery of yawning

resolution

 

mise à jour du
12 avril 2011
Plos One.
2011;6(4):1-4.  
pdf de cet article
Ingroup-Outgroup Bias in Contagious Yawning by Chimpanzees Supports Link to Empathy
Matthew W. Campbell, Frans B. M. de Waal
 
Living Links Center, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, USA

Chat-logomini

-Campbell M et al. Computer animations stimulate contagious yawning in chimpanzees Proceed Royal Soc Biol 2009:276(1676):4255-4259
-Campbell MW, de Waal F. Ingroup-Outgroup Bias in Contagious Yawning by Chimpanzees Supports Link to Empathy. Plos One. 2011;6(4):1-4
-Campbell M, de Waal F. Methodological Problems in the Study of Contagious Yawning; In Walusinski O (ed): The Mystery of Yawning in Physiology and Disease. Front Neurol Neurosci. Basel, Karger, 2010, vol 28, pp 120&endash;127
-Campbell M, de Waal F. Chimpanzees empathize with group mates and humans, but not with baboons or unfamiliar chimpanzees. Proc. R. Soc. B 281: 20140013

Exploring the link between empathy and contagious yawning
Matthew W. Campbell & Frans B. M. de Waal

Empathy: Its ultimate and proximate bases F de Waal
L'âge de l'empathie De Wall F
Empathy and contagion of yawning: A behavioral continuity related to a behavioral discontinuity ?
B Deputte & O Walusinski
Tous les articles sur la contagion du bâillement
All articles about contagious yawning
 
campbell chimps
 
Tara, a chimpanzee, yawns while watching a video of chimpanzees from the group yawning on an iPod. The chimps in the study with Tara yawned 50 percent more frequently in response to video of members of their group yawning versus video of members of another group yawning.
 
Introduction
 
Humans (Homo sapiens) favor other humans seen as belonging to their own group (ingroup) over humans seen as belonging to different social groups (outgroup), even in absence of explicitly stated bias [1,2]. Recently, these biases have been extended to differential brain activity during empathy for pain. Specific brain areas, most notably the anterior cingulate cortex (ACC) and anterior insula, activated during functional magnetic resonance imaging (fMRI) both when subjects experienced pain and when another person present experienced pain, whereas other areas activated only during the direct sensation of pain [3]. Singer et al. [3] interpreted these findings as humans sharing the affective or emotional aspect of pain with others, but not the physical sensation of pain. Extending these findings to bias, two studies presented visuals of painful experiences to human ingroup and outgroup members (as defined by race) while using fMRI to examine brain activity [4,5]. Xu et al. [4] found greater activity in the ACC in response to ingroup empathy for pain than outgroup, and Mathur et al. [5] found differences in the medial pre-frontal cortex, indicating a role of cognitive appraisal. During transcranial magnetic stimulation (TMS) human subjects watched videos of needles penetrating the hand of ingroup or outgroup members, also defined by race [6]. The subjects showed a greater empathic response (in the form of resonant corticospinal inhibition) to the ingroup than outgroup stimuli. Most interesting, subjects also saw needles penetrating a hand that had been artificially colored violet, removing race cues. The subjects responded with a greater empathic response toward the violet hand than the outgroup hand, yielding a pattern of ingroup . violet . outgroup.
 
All three studies showed that humans have differential empathic responses to pain based upon group status, indicating ingroupoutgroup bias. We wanted to explore whether ingroup-outgroup bias is present in contagious yawning. Lehmann [7] and Preston and de Waal [8] both hypothesized that empathy is the mechanism underlying contagious yawning. The idea is that yawns are contagious for the same reason that smiles, frowns, and other facial expressions are contagious. The mechanism that allows someone to reflexively mimic a smile [9] is thought to also allow for reflexive mimicry of yawns. In this article, we use the definition of empathy supplied by Preston & de Waal [8], in which empathy is a term for a broad category of resonant emotional responses comprising a continuum from basic forms, such as emotional contagion, to complex forms, such as cognitive empathy.
 
The link between empathy and contagious yawning has empirical support. Humans who performed better at selfrecognition and theory-of-mind, two abilities that contribute to complex empathy, performed more contagious yawning [10]. In gelada baboons (Theropithecus gelada), the closer the social bond between individuals, the more likely they would yawn when the other yawned [11]. This finding is consistent with the observation that empathy is more pronounced the closer the relationship between individuals [8,12]. Also informative are the negative relationships. Two conditions, schizotypy [10] and the autism quotient [13,14], are associated with decreased contagious yawning, possibly to the point of being absent in autism.
 
Both of these conditions are associated with atypical empathy functioning. Contagious yawning has been documented in five mammalian species: humans [10,13,14,15,16,17], chimpanzees [18,19], stumptail macaques (Macaca arctoides) [20], gelada baboons [11], and domestic dogs (Canis familiaris) [21,22], although some of the interpretations differ. Because of its relevance to human mental health, evolutionary biology, and as a potential low-cost complement to other measures, contagious yawning is a useful and perhaps under-utilized tool for studying empathy functioning.
 
Our hypothesis was that if empathy is the mechanism underlying contagious yawning, then contagious yawning should show the same biases as other measures of empathy, specifically the ingroup-outgroup bias. We tested two groups of captive chimpanzees by showing them yawn and control videos of their own group and the strange group. Chimpanzees form communities that are territorial and exclude neighboring individuals and communities [23].
 
Thus, for chimpanzees, strangers are outgroup by default. Evidence for an ingroup-outgroup bias would be if chimpanzees yawned more in response to watching familiar individuals yawning than strangers. Studying chimpanzees also allows us to test whether human ingroup-outgroup empathy bias is rooted in evolved mechanisms assessing social closeness, familiarity, and group status.
 
Discussion
 
The chimpanzees yawned more in response to the familiar yawn video than the familiar control, demonstrating contagious yawning. However, the video of unfamiliar chimpanzees had no detectable effect, as the difference in yawning between the yawn and control videos was nonsignificant. Critically, the chimpanzees yawned more in response to the familiar yawns than the unfamiliar yawns, demonstrating ingroup-outgroup bias. This bias supports the hypothesis that empathy is the mechanism underlying contagious yawning. The link between empathy and contagious yawning is further supported by our data on attention. The chimpanzees actually watched the videos of unfamiliar individuals more than the videos of familiar individuals.
 
They attended more to the unfamiliar yawns, but yawned more to the familiar yawns. This finding rules out attention per se as a mediating factor and supports the idea that social identification with the stimuli influenced the rate of contagion. Even though all of the ingroup videos were presented before the outgroup videos, we can think of no a priori reasons for an order effect. The attention data show that the chimpanzees did not lose interest in the videos since they watched the outgroup videos more than the ingroup videos. There is no evidence nor are there suggestions in the literature that contagious yawning is transient and fluctuates over time. These same subjects were previously tested and showed contagious yawning [19], so contagion seems to be an enduring behavior. The rate of yawning toward all of the control videos has remained the same over three years (2007&endash; 2010) and three different stimuli, suggesting no change in baseline rates of yawning. The more pertinent order effect would be between the yawn and control videos within a stimulus type (i.e., ingroup or outgroup), but these were always counter-balanced.
 
In contrast to chimpanzees, humans [10,13,14,15,16,17] and dogs [21,22] have shown contagion in response to watching unfamiliar individuals yawn. Some different variables may explain this. First, we cannot rule out that our sample size, large by chimpanzee standards, was too small to detect a significant difference. Chimpanzees may indeed yawn contagiously in response to unfamiliar individuals, but if so the magnitude of the effect is probably small and would require more subjects to detect statistically. A similar situation occurred in the first study of yawn contagion in chimpanzees [18], which had too small of a sample size to detect contagious yawning at the population level (the significant effects were at the individual level). In addition, Anderson et al. [18] did test for ingroup-outgroup bias, but since they could not detect a population-level effect for contagious yawning overall, they did not detect a difference between these stimuli. Larger samples of chimpanzees have shown populationlevel contagious yawning and an ingroup-outgroup effect ([19] and the present study). It may take an even larger sample than the one we had available to detect yawn contagion in response to unfamiliar chimpanzees.
 
We should also be mindful of social structure, as we may have two different factors at work: familiarity and group membership. Chimpanzees are territorial and aggressive toward neighboring communities [23]. Since all members of a community know each other, for chimpanzees, unfamiliar individuals are by definition outgroup individuals. Humans, at some point in our evolution, gained the ability to include unfamiliar individuals in our ingroup. Therefore, humans do not necessarily view strangers as belonging to an outgroup. Pet dogs are accustomed to interacting with unfamiliar humans, and sometimes unfamiliar dogs, in positive ways.
 
Possibly, we artificially selected dogs to, like us, have disassociated familiarity and group status, but this needs testing. Exposed to artificial stimuli that transcend the ingroupoutgroup distinction, chimpanzee yawn contagion shows patterns similar to those of brain imaging studies of empathy. Chimpanzees yawned in response to 3D computer-animated chimpanzees yawning [19]. These animations were not familiar individuals, yet they stimulated contagious yawning. Chimpanzees seem to process animations the same way they process pictures of chimpanzees [25], but the inherent artificiality of the animations may have prevented them from being processed as outgroup individuals. This finding is similar to the greater empathy of humans to pain inflicted on a hand artificially colored purple than a hand of an other-race individual present in society [6].
 
Thus, animations and artificial stimuli may allow us to distinguish between and test the variables of familiarity and group status, in humans and nonhumans alike. Contagious yawning in humans has not yet been tested for biases, including social closeness [11] and ingroup-outgroup bias, but we would expect similar responses. Contagious yawning has several advantages as a measure of empathy given its low cost, high portability, and applicability to multiple species, which may make it a useful complement to physiological, questionnaire, and mental health diagnostic based measures of empathy. Given that chimpanzees exhibit both altruism [26] and extreme violence [23] toward others, studying how and when empathy is engaged may tell us about how humans switch between these two extremes as well.