It’s really common to start yawning after seeing someone else do it. You might even be yawning right now, just reading about it. But we also instinctively know that there’s something a bit rude about yawning: we’re less likely to show this “yawn contagion” when we’re being watched, for instance. And even when we do yawn in the presence of others, we’ll often cover our mouth.
Why does yawning carry this stigma? The obvious explanation is that yawning indicates that we are tired or bored, and we might not want to make others feel like they are the source of that boredom (even if they are!). But the authors of a new study in Personality and Individual Differences have another intriguing theory: we dislike yawning because it can be a sign of disease.
There is some evidence that yawning is related to disease, note Mitch Brown from the University of Arkansas and colleagues. Certain neurological diseases can lead to abnormal yawning, for example, and yawning may become more frequent as someone develops a fever (some researchers argue that one of the purposes of yawning is to cool the brain, though this theory is contentious). Yawns can also indicate fatigue, which is often brought on by illness. The team also points out that covering our mouth hardly hides the fact that we are yawning — in fact, it might even draw attention to it. So perhaps it is more akin to covering our mouths during a cough or sneeze: an action performed to avoid transmitting disease.
To see whether people think of yawning as a disease cue, the team asked 196 American undergraduates to complete various questionnaires. These included measures of their aversion to germs generally and fear of Covid in particular. They also indicated the extent to which they felt disgust in various scenarios, including those related to pathogens (for example, “Accidentally touching a person’s bloody cut”). Finally, participants rated how much they stigmatised yawns, as well as sneezes, coughs, and hiccoughs, by indicating how rude it was to perform that bodily function in front of others and how important it was to cover your mouth when doing it.
The team found that coughing and sneezing carried a higher degree of stigma than yawning, which in turn was stigmatised more than hiccoughing. But importantly, people’s levels of pathogen-related disgust and aversion to germs both predicted how much they stigmatised these bodily functions. Those who scored higher on these measures showed more stigmatisation of yawning, as well as coughing and sneezing (only aversion to germs was related to stigmatisation of hiccoughs).
The researchers argue that this shows we do indeed see yawning as a disease cue. The fact that people who are particularly concerned about disease and germs are more likely to stigmatise yawning — as well as clearer indicators of disease like sneezing and coughing — suggests they may see yawns as potential threats to their health. Fear of Covid didn’t further increase people’s stigmatisation of yawning, and the researchers suggest this shows that the stigma around yawning has “ancestral roots” rather than just cropping up during a pandemic.
However, there could be other explanations for the results. Perhaps people who are concerned about germs would rather avoid someone who is yawning not because it suggests they are sick, but simply because they don’t want to be breathed on. Or maybe these people have an aversion to seeing or thinking about bodily functions in general, whether or not these are actually related to disease. Further studies are needed to disentangle all of these possibilities before researchers can definitively conclude that we use yawns as a disease cue.
The study also doesn’t rule out other reasons that yawning carries a stigma. Yawning can of course indicate boredom and may be interpreted as disrespectful, so covering our mouths may simply be a non-verbal way to communicate that we’re not trying to be rude — even if it doesn’t really hide the yawn. There’s clearly a lot more work to be done to understand the purpose and meaning of this seemingly simple reflex.