Why Does Seeing Someone Yawn Make Us Want to Yawn?

Someone in a waiting room opens their mouth in a yawn, and seconds later you feel the same urge. This is contagious yawning. It differs from the spontaneous yawning associated with tiredness: seeing or hearing a yawn, and even reading about one, can act as a trigger. Yet the response does not occur in everyone on every occasion, and science has not established why it happens.

In one study, 328 adults watched a three-minute video of people yawning, and 222 yawned at least once. Among those tested again, the response was reasonably stable. Age was associated with susceptibility but explained only about 8 per cent of the variation between people. The researchers also measured empathy, sleepiness and cognitive performance. After accounting for age, empathy did not explain who was more likely to yawn. A yawning video can therefore cause a behavioural response, but it cannot reveal a person’s character.

One possible account is that observing an action activates perception–action processes related to performing it. Other accounts emphasise attention, changes in arousal or the synchronisation of groups. These remain candidate mechanisms; “mirror neurons” should not be treated as a single proven answer. Some studies supporting the empathy hypothesis have reported greater contagion between familiar individuals, but findings are inconsistent. A 2020 reanalysis of six dog studies, together with a new experiment, found strong evidence that dogs show contagious yawning but no predicted bias based on familiarity, sex or prosocial behaviour.

The safest conclusion is modest: seeing a yawn can increase the chance of another yawn, while attention and individual differences affect the response. Evidence is still insufficient to establish a social synchronising function or a causal connection with empathy. Failing to yawn does not show that someone is uncaring, and catching a yawn is not a valid empathy test.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0091773
https://royalsocietypublishing.org/rspb/article/287/1920/20192236/85520/Contagious-yawning-is-not-a-signal-of-empathy-no