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
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
http://www.baillement.com

mystery of yawning 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

mise à jour du
23 mars 2014
PLoS One
2014;9(3):e91773
 Individual Variation in Contagious Yawning Susceptibility Is Highly Stable and Largely Unexplained
by Empathy or Other Known Factors
 
Alex J. Bartholomew and Elizabeth T. Cirulli
  

Chat-logomini

 Tous les articles sur la contagion du bâillement
All articles about contagious yawning
 
 
Abstract
 
The contagious aspect of yawning is a well-known phenomenon that exhibits variation in the human population. Despite the observed variation, few studies have addressed its intra-individual reliability or the factors modulating differences in the susceptibility of healthy volunteers. Due to its obvious biological basis and impairment in diseases like autism and schizophrenia, a better understanding of this trait could lead to novel insights into these conditions and the general biological functioning of humans. We administered 328 participants a 3-minute yawning video stimulus, a cognitive battery, and a comprehensive questionnaire that included measures of empathy, emotional contagion, circadian energy rhythms, and sleepiness. Individual contagious yawning measurements were found to be highly stable across testing sessions, both in a lab setting and if administered remotely online, confirming that certain healthy individuals are less susceptible to contagious yawns than are others. Additionally, most individuals who failed to contagiously yawn in our study were not simply suppressing their reaction, as they reported not even feeling like yawning in response to the stimulus. In contrast to previous studies indicating that empathy, time of day, or intelligence may influence contagious yawning susceptibility, we found no influence of these variables once accounting for the age of the participant. Participants were less likely to show contagious yawning as their age increased, even when restricting to ages of less than 40 years. However, age was only able to explain 8% of the variability in the contagious yawn response. The vast majority of the variability in this extremely stable trait remained unexplained, suggesting that studies of its inheritance are warranted.

Spontaneous yawning, which occurs more frequently when one is bored or tired, is a deeply rooted, phylogenetic trait that is widespread among vertebrates [1]. In contrast, contagious yawning, which can be triggered in response to hearing, seeing, reading, or thinking about yawning [2]&endash;[4], has only been definitively demonstrated in humans and chimpanzees[3], [5]. The ability to yawn spontaneously begins in humans in utero by 20 weeks of gestation, but contagious yawning does not reliably develop in humans or chimps until childhood [6]&endash;[9].
 
While much speculative theory has gone into understanding the primary function of yawning, no scholarly consensus has been reached or substantiated. Theories range markedly from a thermoregulatory function, i.e., cooling of the brain and increased oxygen consumption, to behavioral synchronization and communication[10], [11]. The contagious aspect of yawning remains a well-known yet poorly understood phenomenon despite the ability to induce yawning in a laboratory setting from finite stimuli, efforts to identify the underlying neural mechanism, and reported associations with empathy.
 
Evidence for the role of empathy in contagious yawning spans disciplines and has lent support to the empathetic modeling hypothesis[12]. Studies have found susceptibility to contagious yawning to be correlated with empathic aspects like faux pas theory of mind tasks, self-face recognition, and scores on standardized empathy scales [2], [12], [13]. Intriguingly, patients with either autism spectrum disorder or schizophrenia, both of which exhibit impaired social resonance, demonstrate reduced contagious yawning despite spontaneous yawning remaining intact [13]&endash;[15]. Further support for the role of empathy stems from a longitudinal behavioral study demonstrating a positively modulated contagious yawning frequency and latency along the following cline of increasing social bond: stranger?acquaintance?friend?kin[16]. An experiment in chimpanzees, who display at least basic levels of empathy, furthered this finding by demonstrating increased contagious yawning in response to in-group, compared to out-group, yawners[17]&endash;[19].
 
Neuroimaging studies have also provided support for the role of empathy in this trait. Despite divergent reports on the recruitment of the human motor neuron system (MNS), there is general consensus that contagious yawning recruits the neural network involved in cognitive empathy[2], [20]&endash;[22]. The MNS may allow for shared emotional and physiological states based on motor patterns [23] and has been previously demonstrated to be more active in empathic individuals[24]. By evaluating unique patterns of activation during contagious yawning, it has also been demonstrated that structures implicated in self-processing and mentalizing, such as cortical midline structures, are recruited during the contagious yawning response[20].
 
In controlled studies, approximately 40&endash;60% of healthy volunteers yawn in response to a yawn stimulus [3], [4], [12]. Despite this variability, relatively little is known about factors that may influence individual susceptibility to contagious yawning beyond empathy. Purported associations have additionally been made with subjective measures of intelligence, time of day, and climate conditions [7], [25], [26]. However, studies with larger sample sizes have generally not assessed multiple factors simultaneously and have been limited in scope. Additionally, the effect of being observed is inhibitory to contagious yawning[27], [28], which has made studying this trait in a more naturalistic setting a possibly ideal, yet underexplored approach. In particular, no studies have yet assessed whether susceptibility to contagious yawning remains stable when participants are tested both in a laboratory setting and in an uncontrolled setting outside of the laboratory. Only one study has ever assessed whether an individual's susceptibility is stable from one laboratory-based testing session to the next[3].
 
Here, we aim to better define the role of various factors in susceptibility to contagious yawning by systematically assessing the effect of basic demographics, testing conditions, empathy, cognitive performance, time of day, and other variables on the response of healthy controls to a brief contagious yawning video stimulus. We also aim to define the stability of susceptibility to contagious yawning using our developed yawning stimulus in a laboratory and natural setting. Our overall, long-term goal in characterizing variability in this trait is to create a novel viewpoint into the pathways behind human diseases like schizophrenia and autism, as well as general human functioning, by identifying the genetic basis of normal variation in this genetically understudied, yet clearly biological, trait. The presented work represents the most comprehensive characterization of factors influencing contagious yawning to date.
 

Discussion

 
We assessed the impact of multiple factors on contagious yawning susceptibility in a group of 328 healthy volunteers who exhibited contagious yawning frequencies that were similar to those from the previous literature [3], [4]. Our results reveal that variables like empathy, tiredness, and Circadian preference have little effect on contagious yawning susceptibility and that the contagious yawning response of individuals is stable over a two-month period, whether they are tested in the lab, or off-site via an online test.
 
The results demonstrate that the age of the participant was the only variable with a significant influence on whether or not they yawned. This association was not simply the result of the wide range of ages assessed here (Figure 5); even when restricting to participants aged below 40, age was still the only significant predictor of susceptibility to contagious yawning. Despite this strong association, age was only able to explain 8% of the variation in the yawning response, leaving the majority of variation unexplained by any known factors. Interestingly, a reduction in yawning frequency has been previously demonstrated in aged individuals, though never previously in a contagious context [42].
 
Our results are in contrast to previous studies, which have identified correlations between yawning susceptibility and empathic abilities, time of day, and subjective measures of intelligence [7], [12], [13], [25]. The IRI Fantasy, which gauges one's capacity for cognitive empathy and was previously demonstrated to influence susceptibility to contagious yawning in a sample of 45 healthy controls [13], was not a significant predictor of susceptibility in our study when taking age into account, despite the general viewpoint that contagious yawning must be a product of empathy [12], [14], [43], [44]. Our participants were measured for several aspects of empathy, including all four portions of the well-known IRI and an established emotional contagion test. While the sample size for the empathy scales was smaller than the sample size for the rest of our study, the number of participants measured was still larger than the majority of previous studies on contagious yawning and would have been more than sufficient to pick up a strong effect. This lack of association suggests that contagious yawning is not simply a product of one's capacity for empathy.
 
When examining variables individually in univariate logistic regression analyses, we did identify associations between contagious yawning susceptibility and education, whether one was currently a student, cognitive performance, Circadian preference (CIRENS), empathy (IRI Fantasy subscale), and current tiredness. However, these variables were all even more strongly associated with the age of the participant and were no longer significantly associated with contagious yawning susceptibility when taking age into account. While the associations between these factors and age were largely already known to exist [45]&endash;[48], the reason for the association between contagious yawning and age remains unknown, offering a direction for future exploration. Possible explanations for this strong, inverse association could include decreased attention to the stimulus with age, a reduced connection to the yawners in the video due to use of technology, or a general decline in susceptibility to contagious yawning as we age.
 
To our knowledge, only one previous study of 37 participants has measured the test-retest reliability of a contagious yawning susceptibility test [3]. Our work demonstrates high reliability in individual yawn responses to a 3-minute yawn stimulus video, whether it is taken twice outside the lab or once in the lab and then a second time outside the lab. While the correlation between the two test sessions was lower in the in-lab/off-site repeat session, this is not unexpected given the change in testing conditions. Furthermore, both sets of correlations for these repeat sessions are comparable to those of the previous work, despite the difference in our testing locations and even though our studies differed markedly in length, stimulus type and sample size. Our results provide new evidence for the stability of contagious yawning susceptibility across testing sessions and locations and indicate that constant differences exist between healthy controls in their susceptibility.
 
This study does have some limitations. It is worth noting that our goal was not to describe the frequency of yawns in response to a specific video, but rather to reliably measure differences between individuals in their response to a short, standardized yawn stimulus. We therefore make no claims about the precise frequency of contagious yawns elicited by the video stimulus. In addition, participants were primed with a brief description of contagious yawning, which may have contributed to the slightly elevated percentage of contagious yawners in our population; it is also possible that some recorded yawns were actually spontaneous yawns. We did not directly observe the participants, in contrast to many previous contagious yawning studies. This method was chosen because the high word of mouth advertisement about our study makes secretive procedures like surreptitious observation difficult to maintain for all participants. The strong test-retest correlation demonstrates that our method is valid and is in accordance with a previous study showing that participants were able to accurately record their own yawns while being secretly videotaped [39]. Additionally, we employed several self-report scales that may not accurately reflect, for example, the true empathy or circadian preference of the participant. Nonetheless, these scales are either current standards in the field or are well correlated with them, providing us with the best representation of these traits that is available with a brief questionnaire. Finally, we interpreted pseudo r2 values from the logistic regression models as approximations of the amount of variation in contagious yawning explained by the variables investigated, although these values cannot be interpreted as reliably as can the traditional r2 values from linear regression models.
 
Despite these limitations, our work clearly demonstrates the stability of intra-individual variation in susceptibility to contagious yawning, a significant negative correlation between age and the contagious yawning response, and the inability of any known variables to explain the vast majority of variation in contagious yawn responses. This extensive, unexplained, and highly replicable variation between individuals in their susceptibility suggests the existence of an underlying genetic influence and warrants future studies assessing the inheritance of this unique trait.