Yawning is characterized by a powerful gaping of the jaw with inspiration, a brief period of peak muscle contraction and a passive closure of the jaw with shorter expiration1. Although seemingly indistinguishable in the motor pattern, yawns are elicited in two distinct ways. Unlike spontaneous yawning, which is triggered physiologically perhaps due to modified arousal or state changes associated with brain temperature fluctuations2,3,4, contagious yawning is psychologically driven by sensing or thinking about the action. While spontaneous yawning appears to be widespread among vertebrates5, thus far only humans and a limited number of non-human species have been documented to yawn contagiously6,7,8,9,10,11,12,13.

Interest in contagious yawning has grown substantially in recent years, following studies linking individual differences in this response to various measures of perspective taking and empathic processing14,15. The development of this empathic modeling hypothesis has led to research using contagious yawning as a potential dependent measure for assessing empathy in both typically developing and clinical populations. Most recently, it has been reported that individuals scoring higher on a psychopathic personality inventory showed reduced contagious yawning16. Initial reports on the absence of contagious yawning in children with autism spectrum disorder also supported this connection to empathy17,18,19, but subsequent research shows that this result may be a consequence of the reduced tendency for these individuals to attend to others’ faces20,21. In addition, at least one study has failed to demonstrate a correlation between empathy and contagious yawning in healthy populations22. A positive connection between contagious yawning and social closeness/affiliation has been reported in a number of studies8,9,10,23,24,25,26,27,28, though it appears to be age-dependent (i.e., juveniles fail to show this effect)29,30 and at least three studies have failed to demonstrate this relationship in adult populations13,31,32. Consequently, the link between contagious yawning and empathy requires further investigation. Nonetheless, the use of contagious yawning could still prove useful for studying social psychological development if a clear social link was established.

Previous research has demonstrated that a variety of behavioral responses in both humans and non-human animals can be modulated as a function of social presence, a phenomenon sometimes known as the audience effect33,34,35. Furthermore, under brief periods of social crowding, human and non-human primates often limit forms of social interaction (i.e., the elevator effect)36. To date, the social variables influencing the expression of contagious yawning in humans are relatively unknown. Although previous research has reported that yawning frequency is less common among humans in naturally crowded environments5 and in participants being observed by a researcher in the laboratory37, the impact of social presence on contagious yawning has yet to be formally investigated. Here we present the first study to systematically alter the type of social presence experienced by participants in the laboratory to determine its effect on contagious yawning frequency.

One of the defining attributes of research on social presence effects is the wide array of stimuli, other than actual people, that have been demonstrated to induce it (e.g., images of eyes38,39; video cameras40,41; eye trackers42,43). This has led to a critical distinction between two broad types of social presence effects: implied social presence effects and actual social presence effects. In the current experiment we investigate the social component to contagious yawning by presenting stimuli that varied in their degree of social presence. In particular, we compared contagious yawning in an “alone” condition with that behavior in the presence of an image of eyes, a webcam without instructions that it was recording, a webcam with instructions that it was recording, and, finally, an actual person. Thus, the former two manipulations (i.e., eyes, webcam + no instructions) merely suggest that the participant is being watched, whereas in the latter two (i.e., webcam with instruction, real person) this notion is made more explicit. In addition, in the case of the latter two manipulations, where the notion that one is being watched is made explicit, we can contrast an implied presence (i.e., a recording webcam) directly with an actual social presence (i.e., a real person). How contagious yawning varies (if at all) across these different types of social presence will provide novel insight into the influence and sensitivity of contagious yawning to the presence of others.