Why is yawning contagious?
What experiments found about catching a yawn, why closeness shapes who catches it, and what is still debated.
Answer to the question
Why is yawning contagious?
Yawning is contagious because seeing or reading about a yawn can trigger one. In Robert Provine's video study, 55 per cent of adults yawned at yawning faces, against 21 per cent at smiles. Catching is strongest among people who are close, and researchers still debate whether it reflects empathy.
Key takeaways
- In Robert Provine's video study, 55 per cent of 30 adults yawned while watching a five-minute series of yawning faces, against 21 per cent of 30 who watched smiles.
- Reading about yawning triggered yawns in 30 per cent of readers over five minutes, against 11 per cent of those who read about hiccuping (Provine's account).
- Across a year of observation of adults, only social bonding predicted contagion: kin first, then friends, acquaintances and strangers (Norscia and Palagi, 2011).
- Chimpanzees and dogs both yawned more at familiar models than at unfamiliar ones (Campbell and de Waal, 2011; Romero and colleagues, 2013).
- A review of the evidence on a link to empathy found it inconsistent and inconclusive (Massen and Gallup, 2017), and infants and preschoolers did not yawn at clips of yawns, including their mothers' (Millen and Anderson, 2011).
Of 30 adults who watched a five-minute series of yawning faces, 55 per cent yawned. Of 30 who watched smiles, 21 per cent did. Robert Provine reported those figures in his account of years of work on the topic, and they anchor the study of contagious yawning and answer plainly why yawning is contagious: a yawn that is seen tends to be followed by another, with no decision to join in. The cue needs little. Faces with the mouth masked worked as well as intact faces, and a mouth shown alone did no better than a smile, so the open mouth is not what sets it off.
Contagious yawning travels by sight and print
Provine found that the cue does not have to be a picture. Adults who read an article about yawning yawned in 30 per cent of cases over five minutes, against 11 per cent of those who read about hiccuping. A yawn can travel through an idea as well as through a face, which may be why a page on the subject can produce a few.
Spontaneous yawns come from the body of the yawner. Contagious yawns come from outside, and they behave differently: they depend on who is watching and what they are watching. That difference is why researchers treat contagious yawning as a social behaviour and not only a reflex. Provine's reading of his own results is that it may be a primal form of empathy, a suggestion that later work has tried to test in people, chimpanzees and dogs. Catching a yawn is rarely a considered act, which sets it apart from the deliberate imitation weighed in When Copying Is the Rational Move.
Closeness decides the catch
The test run most often in contagious yawning is a simple one: does it matter who yawns? Ivan Norscia and Elisabetta Palagi recorded yawn contagion among adults over 16 for one year in everyday settings. Social bonding was the only variable that predicted how often and how quickly people caught a yawn. Kin showed the most contagion, then friends, then acquaintances, then strangers, and strangers and acquaintances took longer to respond. Nationality and sex did not explain the pattern in that dataset.
The gradient is not confined to people. Matthew Campbell and Frans de Waal showed 23 chimpanzees from two groups videos of familiar and unfamiliar individuals yawning or at rest. The animals yawned more at familiar yawns than at rest or at unfamiliar yawns. In Behave, Robert Sapolsky places this kind of finding among his examples of copying that follows familiarity in primates: a yawn is caught most readily from a familiar chimpanzee, next from a familiar human, then from an unfamiliar human, and not from an unfamiliar chimpanzee.
Dogs show a version of it. In a study of 25 dogs, owners and a stranger acted out yawns or control mouth movements. The dogs yawned more in the yawn condition than in the control, and more when the owner was the model. Heart rate did not differ between conditions, which the authors took as a sign that the yawning was not a response to stress.
| Group | What was compared | What was found |
|---|---|---|
| Adults, video | Yawning faces against smiling faces | 55 per cent yawned at yawns, 21 per cent at smiles |
| Adults, everyday life | Kin, friends, acquaintances, strangers | Contagion fell in that order |
| Chimpanzees | Familiar against unfamiliar yawners | More yawns at familiar yawners |
| Dogs | Owner against stranger | More yawns when the owner yawned |
Empathy and age stay open
The familiarity gradient fits an empathy account, since people tend to respond more to those they feel close to. It also fits a plainer one, in which people look more closely at faces they know, and looking is what the cue needs. Mirror Neurons, the best-known brain account of copying, remain contested: watching someone act engages some of the same regions as acting, and what that means for empathy is debated.
Provine considered mirror neurons an unlikely mechanism and pointed to a brain imaging study in which yawn exposure activated regions linked to processing of the self. Jorg Massen and Andrew Gallup reviewed the evidence on self-reported empathy, familiarity, sex, development and imaging. They found it inconsistent and inconclusive on whether contagious yawning measures empathy, pointed to confounds such as visual attention and social inhibition, and called for objective measures in future work.
That leaves a clear division between what is established and what is not. That contagious yawning is real, that it can be triggered by sight or reading, and that it follows closeness in several species is well supported. Why closeness matters is the open part. The broader picture of how feelings and actions pass between people is set out in What is emotional contagion, and the way closeness sorts people into those we copy and those we do not is the subject of What is in-group bias.
Development adds a further clue, because yawning itself starts early. Provine notes that spontaneous yawning begins in the womb, as early as the twelfth week. Contagious yawning arrives much later. In two studies, Ailsa Millen and James Anderson asked parents to log their child's yawns for a week and then showed infants and preschoolers video clips of yawning, including their own mothers. None of the logged yawns was contagious, and none of the children yawned in response to the clips.
The same study found that children's own yawns followed the daily pattern seen in adults, with peaks after waking and before bedtime. The habit of catching a yawn develops later than the yawn itself, and it was absent in the children even when the clip showed their own mother.
Common questions
Why is yawning contagious?
Seeing or reading about a yawn can trigger one. In Provine's video study, 55 per cent of adults yawned at yawning faces against 21 per cent at smiles, and catching is strongest among people who are close.
Does reading about yawning make you yawn?
It can. In Provine's account, 30 per cent of adults who read about yawning yawned over five minutes, against 11 per cent who read about hiccuping.
Do animals catch yawns from each other?
Chimpanzees and dogs have both shown contagious yawning, and both yawned more at familiar models than at unfamiliar ones.
Do babies catch yawns?
In Millen and Anderson's studies, infants and preschoolers did not yawn in response to video clips of yawning, including their own mothers. Contagious yawning appears later.
Sources
Sapolsky, R. Behave. Seed book; vault hub Books/Behave.
Provine, R. R. (2005). Yawning. American Scientist, 93(6), 532-539. doi:10.1511/2005.56.532 https://doi.org/10.1511/2005.56.532
Norscia, I., & Palagi, E. (2011). Yawn contagion and empathy in Homo sapiens. PLoS ONE. doi:10.1371/journal.pone.0028472 https://doi.org/10.1371/journal.pone.0028472
Campbell, M. W., & de Waal, F. B. M. (2011). Ingroup-outgroup bias in contagious yawning by chimpanzees supports link to empathy. PLoS ONE. doi:10.1371/journal.pone.0018283 https://doi.org/10.1371/journal.pone.0018283
Romero, T., Konno, A., & Hasegawa, T. (2013). Familiarity bias and physiological responses in contagious yawning by dogs support link to empathy. PLoS ONE. doi:10.1371/journal.pone.0071365 https://doi.org/10.1371/journal.pone.0071365
Millen, A. E., & Anderson, J. R. (2011). Neither infants nor toddlers catch yawns from their mothers. Biology Letters, 7(3), 440-442. doi:10.1098/rsbl.2010.0966 https://doi.org/10.1098/rsbl.2010.0966
Massen, J. J. M., & Gallup, A. C. (2017). Why contagious yawning does not (yet) equate to empathy. Neuroscience & Biobehavioral Reviews, 80, 573-585. doi:10.1016/j.neubiorev.2017.07.006 https://doi.org/10.1016/j.neubiorev.2017.07.006