Why yawns are contagious youtube

The individual identity of the subjects trigger and potential responder was included as random factor. The social bond significantly predicted the occurrence of auditory yawn contagion, which was highest between friends and family members.

These results confirm that social bond is per se one of the main drivers of the differences in yawn contagion rates between individuals in support of the EBH of yawn contagion. Yawning is an involuntary sequence of mouth opening, deep inspiration, brief apnea, and more or less slow expiration Baenninger, ; Walusinski and Deputte, ; Guggisberg et al. When elicited, a yawn cannot be totally suppressed.

Therefore, it has been defined as a stereotyped or reflex-like pattern Lehmann, ; Provine, In Homo sapiens , several hypotheses have been put forth with variable support to explain mechanisms and functions of spontaneous yawning, such as oxygenation respiratory function caused by hypoxia , stress-related behavior caused by arousal , or thermoregulation caused by hyperthermia; Guggisberg et al.

In human and non-human primates, depending on the species, when yawning is shown to others, it can communicate threat Troisi et al. In humans, yawning is a socially modulated response because it can be inhibited by actual—and not virtual—social presence Gallup et al. Yawn contagion can be elicited even if the yawn is heard but not seen Arnott et al. In humans, their phylogenetically closest ape species chimpanzees: Pan paniscus ; bonobos: Pan troglodytes and the African monkey Theropithecus gelada , contagious yawning is not only present Provine, ; Palagi et al.

Two main arguments have been presented to explain this social asymmetry in contagious yawning, which have been grouped into two main hypotheses: the Emotional Bias Hypothesis EBH , linking contagious yawning to emotional transfer, and the Attentional Bias Hypothesis ABH , which considers contagious yawning as a motor response that is subject to differences in top-down attentional processes Palagi et al.

The EBH predicts that the social asymmetry observed in yawn contagion rates reflects differences in the different social bonding, a proxy of emotional bonding, between individuals. This hypothesis is supported by evidence that yawn contagion rates follow an empathic trend sensu Preston and de Waal, , being highest between individuals sharing a strongest emotional bond. Specifically, Norscia and Palagi found that in humans yawn contagion rates are greatest in response to kin and friends than in response to acquaintances and strangers.

In adult chimpanzees yawn contagion is higher between in-group compared to out-group members Campbell and de Waal, and in bonobos yawn contagion rates are greatest between individuals that affiliate more with one another Demuru and Palagi, In a comparative investigation including both humans and bonobos, Palagi et al.

Yawn contagion rates increase from infancy to adulthood also in chimpanzees Madsen and Persson, The ABH predicts that the social asymmetry observed in yawn contagion can be due to differences in social, visual attention Massen and Gallup, In particular, highest levels of contagious yawning would be due to the extra top-down, selective visual attention paid to individuals that are more relevant to the observer, such as familiar subjects, as it occurs in humans and geladas, or dominants, as it occurs in chimpanzees or bonobos Yoon and Tennie, ; Massen et al.

In this study, we analyzed data on yawning collected over 9 years on humans in their natural settings and we extrapolated the cases in which the yawn emitted by a subject could be heard but not seen by a potential responder auditory yawn.

By considering only the cases in which the visual cue of the yawning stimulus was not detectable, we verified whether the social asymmetry previously observed in yawn contagion rates persisted or not. In particular, we tested the following alternative predictions derived from the two hypotheses presented above EBH and ABH. Prediction 1a: according to the EBH, the rates of yawn contagion are influenced by the strength of the inter-individual social bond—a proxy of the emotional bond— per se and not by a different top-down, selective visual attention paid to certain individuals in particular.

If this hypothesis is supported, we expect to observe the social bias also when the visual cue of the yawning stimulus is excluded and the rates of auditory contagious yawning to be higher between strongly bonded compared to weakly bonded individuals.

Prediction 1b: according to the ABH, the higher levels of yawn contagion between strongly bonded compared to weakly bonded individuals would be linked to the closest top-down, selective visual attention that individuals pay to individuals that are relevant to them, e. If this hypothesis is supported, the social bias observed in the yawn contagion should disappear when only auditory yawns are considered because the visual cue cannot be attended by the potential responder.

For this study, we considered the vocalized yawns emitted by a subject that could only be heard—but not seen—by a potential responder hereafter: auditory yawns.

Specifically, auditory yawns were collected from November to May , from The auditory yawn database included yawner-potential responder dyads. Depending on the situation, the information was recorded, unnoted, through alphanumerical codes and entered directly into calculation sheets, typed in mobile phones or written on paper, and then entered in calculation sheets for subsequent elaboration. Basic information such as age and the relationship between people was known to the authors.

Trigger and responder were never completely isolated e. Hence, we considered the yawn responses occurring within a 3 min time window from the yawn emitted by the trigger. To further reduce the autocorrelation bias, in case of a chain of yawns emitted by the trigger more yawns emitted in the 3-min time window we registered as a response only the first yawn performed after the perception of the last yawn.

The database see Supplementary Data Sheet included 84 males, 69 females, 16 youngsters yo , adults ad , and 15 senior se. We fitted the models in R R Core Team, ; version 3. We established the significance of the full model by comparison to a null model comprising only the random effects Forstmeier and Schielzeth, As the response variable was binary, we used a binomial error distribution.

We tested whether the interaction between the sexes or the age classes of the trigger and the responder were significant, but as they were not, we did not include them in the model. We used a multiple contrast package multcomp to perform all pairwise comparisons for each bonding levels with the Tukey test Bretz et al. We reported the Bonferroni-adjusted p -values, estimate Est , standard error SE , and z -values. As we found at least one predictor was having a significant impact on the response, we moved on with a drop1 procedure.

The GLMM also indicated a significant effect of the sex of both triggers and responders, and of bonding see Table 1 : yawn contagion of female responders was higher compared to males Figure 3 , and males, as triggers, were responded to more frequently by others compared to females Figure 2. In contrast, we found no significant main effects of the age of both triggers and responders, the time slot in which yawns were emitted, and interaction between the sex of the subjects Table 1.

Line plot of the effect of the social bond between trigger and responder X -axis on the mean occurrence of acoustic yawn contagion Y -axis. Line plot of the effect of the sex of the trigger X -axis on acoustic yawn contagion mean occurrence Y -axis. Effect of the trigger sex on acoustic yawn contagion when the responder is a female right and a male left.

Line plot of the effect of the sex of the responder X -axis on acoustic yawn contagion mean occurrence Y -axis.

Effect of the responder sex on acoustic yawn contagion when the trigger is a female right or a male left. This study shows for the first time that yawn contagion is significantly affected by the social bond between individuals Table 1 even when the triggering stimuli are auditory yawns, which we defined as vocalized yawns that could be heard but not seen visual cue undetectable, auditory cue detectable.

In particular, auditory contagious yawning is significantly more frequent between kin and friends than between strangers and acquaintances Figure 1. This finding supports prediction 1a based on the EBH and not prediction 1b based on the ABH, leading to the conclusion that in humans top-down, selective visual attention cannot be the main driver of the social asymmetry observed in yawn contagion rates Norscia and Palagi, ; Norscia et al.

Contrary to Bartholomew and Cirulli , we found no age effect on yawn contagion, most probably because our database on auditory yawns had a strong prevalence of adults 25—64 years old. The highest levels of auditory yawn contagion in women compared to men confirm the gender bias observed in naturalistic conditions on humans susceptible to yawn contagion by Norscia et al. The gender bias is also in partial agreement with previous results obtained in controlled settings, including the visual cue Chan and Tseng, ; but see Norscia and Palagi, ; Bartholomew and Cirulli, It has been hypothesized that the high degree of yawn contagion in women might inform emotional contagion Norscia et al.

However, this issue is still under debate because cultural differences across human societies can mold social bonding dynamics in a different way. It is therefore complicate, at this stage of knowledge, to disentangle cultural factors, inter-personal relationship quality, and gender influence in the distribution of yawn contagion.

Indeed, the perception of voice gender primarily relies on the fundamental frequency that is on average lower by an octave in male than female voices, with lower frequency vocalizations traveling further than high frequency ones Marten and Marler, ; Latinus and Taylor, However, to our knowledge, there is no specific study addressing the possible gender bias in yawn audibility and further investigation with experimental trials in controlled condition is therefore necessary to verify this speculation.

In this study, we also found that the differences in yawn contagion rates across categories family and friends, strangers, and acquaintances cannot be explained by differences in top-down, selective visual attention.

This finding is in line with previous literature. Contagious yawning appears to involve brain areas that are more related to the orienting-bottom up network [temporoparietal junction TPJ , brainstem nuclei, ventrolateral prefrontal cortex vlPC ] than top-down related areas [frontal eye fields FEFs , intraparietal sulcus IPS , parietal areas; for a review: Palagi et al.

Moreover, yawn contagion is neither sensitive to the sensory cues present in the signal auditory, visual, or audio-visual Arnott et al. Chan and Tseng found that the ability to detect a yawn as such perceptual detection sensitivity was related to the duration of gaze to the eyes of the stimulus releasing face, but eye-gaze patterns were not able modulate contagious yawning.

In chimpanzees, contagious yawning frequencies were highest between same-group than different-group individuals, even if the responders looked longer at out-group chimpanzee videos Campbell and de Waal, The argument that visual selective attention can bias yawn contagion rates in a specific direction subjects responding more to family than strangers is also undermined by the absence of any specific pattern of social attention in human and non-human primate.

Kawakami et al. The same study also revealed that visual attention did not depend on the target race. By measuring how long the experimental subjects gazed at the screen, Whitehouse et al. By measuring glance rates, Schino and Sciarretta observed that mandrills looked more at their own kin than at non-kin but also more at dominant than at subordinate group mates. Therefore, these studies used to support ABH describe no single pattern of selective attention.

One further important point to consider is the very definition of familiarity and group-membership adopted by most of the studies used to support ABH Massen and Gallup, Instead, familiarity or group-membership were defined on the ground of indirect knowledge e. This definition is fine for the purposes of these studies but it is not as much fine if the results are used to propose alternative explanations for the influence that real social bonding—based on real relationships—may have on a phenomenon, in this case yawn contagion.

For example, Michel et al. In ASD children, yawn contagion can be absent Senju et al. In a recent study, Mariscal et al. This finding is in line with the EBH hypothesis that links yawn contagion rates to social bonding, which can reflect emotional bonding. Our study adds to the discussion over the mechanisms underlying the social asymmetry in yawn contagion for a critical reviews: see Adriaense et al.

Bottom-up attention is primarily lead by the sensory perception of the eliciting stimulus whereas top-down, selective attention is a voluntary, sustained process in which a particular item is selected internally and focused upon or examined Katsuki and Constantinidis, In this respect, the acoustic stimulus auditory yawn emitted by the trigger was heard and could elicit a yawning response in the receiver, even though the receiver was not paying any voluntary visual attention to the trigger.

Moreover, the yawning response rates were socially modulated, with auditory yawn contagion being highest in individuals that were most strongly bonded to one another. Hence, top-down selective attention is not the main driver of the social asymmetry observed in yawn contagion, which appears to be a stimulus driven phenomenon-related to bottom-up attention processes.

Further investigation is necessary to understand whether and in what way other forms of attention or pre-attentive stages are able to affect yawn contagion. Written informed consent for participation was not required for this study in accordance with the national legislation and the institutional requirements. IN and EP carried out data collection and conceived and wrote the manuscript. AZ helped with data collection and manuscript revision, figures, and tables.

MG carried out statistical analyses and wrote the related part of the manuscript. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors wish to thank Prof. Roberto Barbuti and Prof. Cristina Giacoma for having supported the research at the University of Pisa and the University of Turin, respectively. National Center for Biotechnology Information , U.

Journal List Front Psychol v. Front Psychol. Published online Apr 3. Author information Article notes Copyright and License information Disclaimer. This article was submitted to Consciousness Research, a section of the journal Frontiers in Psychology.

Received Nov 10; Accepted Feb The use, distribution or reproduction in other forums is permitted, provided the original author s and the copyright owner s are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

This article has been cited by other articles in PMC. CSV 7. Keywords: emotional contagion, bottom-up attention, selective attention, top-down attention, yawn contagion, mimicry.

Introduction Yawning is an involuntary sequence of mouth opening, deep inspiration, brief apnea, and more or less slow expiration Baenninger, ; Walusinski and Deputte, ; Guggisberg et al. Materials and Methods Data Collection and Operational Definitions For this study, we considered the vocalized yawns emitted by a subject that could only be heard—but not seen—by a potential responder hereafter: auditory yawns.

Open in a separate window. Recently, the mirror neuron system of the brain, a collection of neurons in the right posterior inferior frontal gyrus has been suggested to be involved in contagious yawning. The results of a study conducted by Norscia and Palagi[ 33 ] have provided evidence for the fact that the social bond associated with empathy affects the yawn contagion in humans in terms of occurrence, frequency and latency.

A total of bouts of yawning were observed, out of which only were analyzed, since only they could be definitely assigned as being triggered in an observer by a specific audio-visual contact with a yawner, within a 3 min time slot.

The importance of the social bond in shaping the yawn contagion demonstrates that empathy and yawning are strongly correlated. The link between empathy and contagious yawning is further supported by the data collected by Campbell and de Waal. The ingroup videos were shown before the outgroup videos to all the subjects. It was ensured that all the subjects paid similar attention to both types of videos. Each chimpanzee was exposed to the videos for a total of 20 min on one or more days, depending upon his interest and cooperativeness, to eliminate the effect of stress.

Also, none of the test subjects were able to see the other chimpanzees while viewing the videos. Even though, the authors do maintain that their results suggest a possible relationship between yawning and empathy, yet they also admit a few limitations of their study.

This may be due to the fact these animals are territorial and form small coteries, which are aggressive to neighboring ones.

Such a kind of behavior is absent in humans since the latter do not always view strangers as belonging to an outgroup. It is thus concluded that yawning may be a part of action repertoire of empathic and communicative processes in adult humans and some other mammals which provide for a strong social role of yawns in these species.

Yawning relieves the ear discomfort and hearing problems that are commonly experienced by people during rapid altitude changes in airplanes and elevators. This is achieved by opening of the eustachian tubes due to the contraction and relaxation of tensor tympani and stapedius muscles.

An crucial experimental evidence that provides support to the above proposition comes from the work of Winther et al. The contrast material was detected in middle-ear by computerized tomographic scan of the temporal bone. However, since the eustachian tube can also be opened by swallowing and Valsalva manoeuvre, thus yawning, by itself, does not appear to offer an indispensable evolutionary advantage of releasing middle ear pressure.

The latter effect thus does not seem to be the primary purpose of yawning. For the past several centuries, a commonly held notion associated with yawning is that it is triggered when blood or brain oxygenation is insufficient, that is, when oxygen O 2 levels decrease and carbon dioxide CO 2 concentration rises. However, this belief has been discarded in wake of the results of a recent study in which the yawning frequency was unaffected in subjects who breathed air mixtures containing either more than normal CO 2 or even pure O 2.

Yawning research is intriguing because the ubiquity of this phenomenon across most of the vertebrate classes and even in a 20 week old human fetus,[ 9 ] suggest that considering it merely as an act of boredom and drowsiness is unjustified and that it may have a definitive underlying physiological importance which needs to be meticulously explored. However, till we get a conclusive answer, it is safe to assume that yawning could represent a para-linguistic signal that may have multiple functional outcomes across various species.

The authors would like to thank Robert R. Provine and Oliver Walusinski for their invaluable online archive of articles on yawning, which greatly facilitated the research for literature for this article.

Source of Support: Nil. Conflict of Interest: None declared. National Center for Biotechnology Information , U. Sharat Gupta and Shallu Mittal 1. Author information Article notes Copyright and License information Disclaimer. Address for correspondence: Dr. E-mail: ni. Received Aug 20; Accepted Mar This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.

This article has been cited by other articles in PMC. Abstract Although yawning is a commonly witnessed human behavior, yet it has not been taught in much detail in medical schools because, until the date, no particular physiological significance has been associated with it.

Keywords: Arousal, brain thermoregulation, empathy, yawning. Footnotes Source of Support: Nil. Askenasy JJ. Is yawning an arousal defense reflex? J Psychol. Provine RR. Yawning as a stereotyped action pattern and releasing stimulus. Am Sci. Simonds AK. Curbside consult: Why do people yawn? West J Med. Walusinski O. Popular knowledge and beliefs.

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