I'm Not Tired, You're Tired: Contagious Yawning
What (surprisingly interesting) research tells us about yawns.
Posted Nov 05, 2019
Yes. You’re probably going to yawn while you read this. Writing this piece, and reading research on yawning, I’ve been yawning nonstop, uncontrollably. And it's not because research on yawning is boring—in fact, I was surprised to find just how interesting and complex it actually is.
We all recognize that yawning is contagious. We see someone yawn, and we yawn back. “Stop it,” we will even say, when we see someone yawn, because we know we’re going to have to yawn as well.
If you try to suppress your yawn consciously, it’s rarely successful. You can’t rub your upper lip to stop the desire like you can a sneeze. Why? Why on earth is yawning so contagious? Is it that way for everyone? And by the way, what is yawning for, anyway?
Common thinking has been, for many years, that yawning is about getting more oxygen into your blood. A big yawn, a big breath, gets you oxygenated when you’re tired. But this is another place where common sense, and this medical-sounding explanation, turn out to be wrong.
Yawning doesn’t occur more frequently when our O2 sats are low, and yawning doesn’t change the O2 levels in our blood. Like most human behaviors, yawning probably serves a variety of functions, and yawning still, surprisingly, remains a bit of a mystery. Current research suggests that one big piece of the puzzle is that yawning may cool our brain. When we yawn, it changes the shape of our head and neck, affecting blood flow and resulting in a slight temperature drop in our brains.
But if yawning is about cooling off our brain, why on earth is it contagious? Seeing another person yawn doesn’t make my brain hotter, or make it need cooling off. Recent research explored this connection between temperature regulation and contagion.
In this study, published in the journal Physiological Behavior, participants held cool packs or warm packs to their carotid artery (which is in your neck, supplying blood to the brain). They were then shown a “contagious yawning stimulus,” i.e., a video of someone yawning. Participants who had held the cool pack to their brain’s blood flow were much less likely to yawn contagiously (48.5 percent yawned in response to the stimulus) compared to the warm pack group, where 84.8 percent yawned contagiously. So, our sensitivity to contagious yawning is somewhat context-dependent, affected by our own brain temperature.
Susceptibility to yawning contagion may be impacted by other personal variables as well, including neurochemistry. People with autism, or ASD, appear to be less likely to yawn when they see someone else yawn. Some have suggested this may be due to a lack of attentiveness to other people, but some researchers have controlled for this and shown that attentional components don’t appear to be predictive of yawning susceptibility in people with autism.
However, one study found that in adolescents with autism, higher levels of oxytocin predicted greater susceptibility to yawning contagion, though oxytocin levels were not predictive of yawning susceptibility in adolescents without autism. In a study with college students, intranasal oxytocin did not increase yawning contagion but actually led to individuals making more effort to conceal their yawning, showing greater awareness of the social stigma around public yawning.
Interestingly, injections of oxytocin can induce yawning in rats, though, at this time, it’s unclear if this effect is related susceptibility to contagion or another effect. There is now a model to measure and assess yawning contagion in rats in order to further assess this. But yawning contagion in animals has been measured and identified, particularly in chimpanzees, where statistical analysis of yawning in a troop of chimps suggested strongly that there was a contagious effect.
If adults see a baby yawn, the adult is likely to yawn back, but the reverse isn’t true. Infants are able to distinguish that a yawn in an adult is different from other mouth movements, but infants don’t appear to have developed the other cognitive mechanisms that underlie yawning contagion. The presence of other people in our social environment impacts, and decreases, our susceptibility to yawning contagion.
An interesting study used virtual reality goggles and found that when researchers were present in the room (even when the participant couldn’t actually see them), it inhibited yawning susceptibility. Perhaps the presence of others introduces other social cues, reducing the impact of yawning stimuli. Alternatively, it could be our awareness of the presence of others that inhibits this response, whether from politeness or even fear of embarrassment.
So, it appears that yawning contagion reflects some aspects of social empathy, revealing an awareness of others’ behaviors, cueing some involuntary behaviors in some situations and circumstances, but not others. This cue interacts with aspects of individual predispositions, including empathic sensitivity, an individual’s level of tiredness, and even the temperature of their brain. A somewhat similar pattern is observed in vomiting, where seeing another person vomiting can induce feelings of nausea in observers, something that some have suggested serves an evolutionary-influenced, protective role from toxins.
Somewhat surprisingly, there’s still a lot that is not known about yawning. It’s actually pretty wild that such a universal human experience is still such a mystery. Interestingly, there is an upsurge in relevant research in this area, as further investigation of it reveals sophisticated biological and psychological mechanisms.
As with all studies in human behavior, however, we have to plan for preregistered studies, good research designs, and replications of results. Some of the studies mentioned above were single, interesting studies, but until their results replicate and hold consistent, we must be cautious in interpreting these findings.
By the way—my uncontrollable yawning finally stopped after I exercised, hung out with friends, and took a cool shower. I have no idea if the blood flow and temperature adjustments influenced my yawning, or if taking my mind off yawning changed my susceptibility. If you are yawning in response to this article, you might try similar strategies, cool your head down, get out and socialize, exercise, or get your mind off it.