Yawning is characterized by a powerful gaping of the jaw with deep inspiration, followed by a temporary period of peak muscle contraction and a passive closure of the jaw during expiration1. Physiologically, yawns enhance intracranial circulation2 and facilitate brain cooling3,4,5, which in turn could serve to promote cortical arousal6 and state change7 during behavioral transitions. Contagious yawning, which represents the reflexive triggering or release of this response as a result of sensing yawns in others, is a well-documented phenomenon in humans, as seeing, hearing and even thinking about yawning can induce yawn contagion7,8. Evidence for contagious yawning is also present in a small number of non-human animals, including some non-human primates, birds and domesticated dogs9.

Spontaneous and contagious yawns represent intrinsically connected, yet distinct behaviors. Although indistinguishable in the motor action pattern described above, a number of important factors, in addition to their triggers (i.e., physiological vs. social), differentiate these two types of yawns. Spontaneous yawns, or similar mandibular-gaping patterns, appear to be a phylogenetically old and conserved across vertebrate classes10, while contagious yawning is a more recently derived feature present in only a few highly social species11,12. Consistent with this view, these two responses show distinct ontogenies, with spontaneous yawns emerging early on within intrauterine development in humans13, while contagious yawns do not appear until early childhood14. Furthermore, spontaneous yawns seem to be a universal act across members of a given species, whereas the expression of yawn contagion appears to show much more individual variability. For example, depending upon the methods and stimuli used, only ~30–60% of people show contagious yawning across laboratory and semi-naturalistic settings7,8,15,16,17, with similarly variable response rates observed for non-human primates18.

The fundamental differences between these two yawn-types have led some researchers to propose that yawn contagion may reflect a form of higher-level social-cognitive processing (e.g., emotional contagion or state matching)19,20,21. Indeed, a large body of research has explored the proposed connection between yawning and empathy, with lines of supporting evidence coming from correlational studies15, in-group/out-group comparisons22, neuroimaging investigations23, and clinical studies24. Consistent with this view, one study even showed a negative association between contagious yawning and measures of psychopathy in a non-clinical population25. However, a recent review of this literature concluded that the empathy/contagious yawning link is weak and inconsistent, with the majority of studies failing to observe the predicted effects derived from this empathy modeling hypothesis9. In fact, recent experiments have shown that the susceptibility to contagious yawning among humans is tied to the perceptual encoding of the act in others and is unrelated to psychological traits linked with empathy or emotional processing26. Others have argued that it is not necessary to implicate a link between contagious yawning and higher-order cognitive processes27,28. For example, given the physiological consequences of this motor action pattern (i.e., enhanced intracranial circulation and brain cooling), the spreading of this response through contagion could have evolved to coordinate group arousal or activity patterns and promote collective vigilance16,29. Further research in these areas is needed, but the fact that individual differences in contagious yawning may predict important aspects of psychological and perceptional functioning deserves further attention.

Despite the involuntary and impromptu nature of yawns, and the potential benefits from this action, the expression of yawning is often stigmatized in social settings. In fact, yawns are interpreted as a sign of boredom and disrespect across different cultures30. This seemingly widespread, negative public perception surrounding yawning is presumably a result of the temporal associations between reduced states of alertness and sleep/wake cycles31,32, i.e., yawns are known to occur when individuals are bored or drowsy so this act might indicate one’s disinterest or reduced mental status. Some researchers have therefore speculated that yawning serves a primary communicative role, in which yawns signal internal states to others33,34. However, a central signaling perspective fails to take into account that spontaneous yawns are widespread among solitary species, and often occur when alone even among gregarious animals11,35. Moreover, yawns are triggered by a multitude of factors, and are associated with a markedly variable array of contexts, stimuli and internal states (i.e., not just when we are bored or sleepy)7,36, and as a result could not serve as reliable signals. Nonetheless, the presence of others, i.e., audience or mere presence effects37,38, tends to diminish the expression of yawning. Early research has shown that spontaneous yawns are indeed less common among people in crowded environments10, as well as when being observed by a researcher in a laboratory39. It is unclear whether the reduced tendency to yawn in these settings is due to the negative signaling value of this response to others (i.e., a top-down mechanism), or from heightened arousal levels produced by these contexts that would act to naturally reduce yawning.

Similar socially-modulated effects have been observed for the expression of contagious yawning. The administration of intranasal oxytocin, a hormone and neuropeptide that enhances social perception and awareness40, has been shown to increase the likelihood that people actively inhibit and conceal their yawns, while also decreasing the tendency for any expressed yawns to be accompanied by overt cues of the response41. In comparison to those receiving a placebo saline solution, participants administered 30 IU of intranasal oxytocin were more likely to stifle their urge to yawn and required a greater length of exposure to a contagious stimulus prior to yawning. Moreover, among those that actually showed yawn contagion, individuals that received oxytocin were more likely to cover their mouth and clench their jaw during the act of yawning, and were less likely to display bodily stretching and produce auditory sighs during this response41.

In a more recent and targeted investigation of audience effects on yawn contagion, we explicitly examined how varied degrees of social presence in a laboratory setting altered contagious yawning42. Given the wide array of stimuli that elicit social presence effects, we tested how both implied (i.e., a “recording” webcam facing the participants) and actual social presence (i.e., a researcher in the testing room) influenced contagious yawning to video stimuli presented on a computer monitor. The results from this experiment showed that both implied and real social presence significantly diminished the self-reported expression of yawn contagion in comparison to control settings (e.g., a webcam that is off or a testing room that does not contain a researcher). Participants in the “recording” webcam or researcher present conditions also reported a greater urge to yawn without doing so when viewing the video stimuli42. Thus, the prospect, or actual presence, of others watching seems to inhibit even this inherently social form of yawning.

As an extension of this line of research, here we conducted five experiments to investigate the effects of real-world social presence on contagious yawning in virtual reality (VR). Although not without its limitations, utilizing VR in experimental psychology and the cognitive sciences offers numerous advantages43,44, providing greater levels of control and manipulation over traditional experimental procedures/settings. Furthermore, the capability of VR to potentially block out the external environment and engage the audience with its own stimuli allows for a level of immersion that typical displays cannot provide45. This is the first study to our knowledge which leverages VR to study the factors influencing yawning.

We first assessed how actual social presence in the testing environment (i.e., a live researcher present) altered contagious yawning in VR, and then how both implied and actual forms of social presence within the virtual environment (i.e., embedding recording devices and humanoid avatars within the scene) modified this response (Fig. 1). In particular, the first experiment compared participant responses to contagious yawning stimuli presented in VR between conditions where a researcher either indicated that they would be sitting in the testing room during the virtual testing or not. The second and third experiments examined how the presence of an implicitly or explicitly recording webcam embedded within VR altered contagious yawn response rates within this setting. In the second experiment, the virtual webcam was either accompanied by a red light or not, while in the third experiment the researcher specifically instructed participants in advance that the webcam in the simulation would be recording their behavior during testing, or there was no mention of this device. The fourth experiment assessed how the presence of a motionless humanoid avatar within the scene influenced contagious yawning responses in VR. In particular, contagious yawning was compared between conditions when this figure was directly facing and looking towards the participants or was oriented 180 degrees in the opposite direction facing away. Lastly, the fifth experiment examined how contagious yawning was influenced by the presence of an onlooking humanoid avatar using a more realistic and representative virtual simulation. In particular, the humanoid avatar in this experiment swayed slightly and moved its limbs in a realistic way, mimicking natural behavior, and the virtual scene was designed to represent a more typical laboratory environment similar to our past research42 with a smaller presentation screen positioned on a desktop (Fig. 2). Thus, the design of this experiment allowed us to test the effect of avatar realism and display/room size and appearance. This final experiment also measured the immersive properties of the VR experience (including a sense of presence)46 to assess whether this varied between conditions and influenced yawning rates. In short, our operationalization of social presence both in the real world and in VR involved reproducing stimuli that are known to affect performance in actual reality (e.g., an active webcam, a person) in a VR environment. Note, however, that whether these stimuli will have the same effect in VR as in actual reality is very much an open question as the social presence of items in VR may require some level of psychological involvement and/or behavioral engagement47.

Figure 1 Depiction of varying VR stimuli for Experiments 1–4, including the presentation screen and social presence manipulations (not exhaustive). (a) Depicts the VR presentation for both conditions in Experiment 1; (b) depicts the high social presence condition for Experiment 2; (c) depicts high social presence condition for Experiment 4; (d) depicts the low social presence condition for Experiment 4. Full size image

Figure 2 Depiction of the VR environment for Experiment 5. Designed to represent a typical laboratory experience, participants were instructed to sit down at the desk prior to the stimulus presentation. Full size image

To the extent that placing a participant in a VR situation diminishes awareness or concern regarding the world beyond the VR setting, by inducing a mental state in which the user feels as though they are present within and can act upon the computer environment48, we made the following predictions based on the conditions of each experiment. For Experiment 1, unlike Gallup et al.42, we predicted that the presence of a researcher in the testing room would be equivalent to having no researcher in the room. In contrast, we predicted that placing a recording webcam in the VR environment (Experiment 2) or explicitly referring to the recording VR webcam (Experiment 3), would create an implied social presence and reduce the number of yawns and/or increase the urge to yawn without doing so. Similarly, we predicted that the actual presence of a humanoid avatar in the VR setting or having that person look at the participant (Experiments 4 and 5) would yield behaviors indicative of yawn inhibition, i.e., reduced yawn frequency and/or an increased urge to yawn.