Why Do People Yawn? Uncovering the Reasons and Biology
We have all in our lives yawning while up past our bedtimes, zoning out in a lecture hall, or on the plane to help clear our ears. While yawning has long been associated with either drowsiness or boredom, it’s a not-so-fully-explored reflex.
In fact, one 2024 review concludes that there is still no consensus on the primary function of yawning, though various hypotheses abound. Indeed, all types of theories run the gamut-a brain-cooling mechanism, a method for jump-starting alertness. To gain a little insight into why we yawn, we spoke to Dr Laura Purdy, a board-certified family medicine physician, and Dr David Smith, co-founder of the online medical goods store Bladgo, taking a look at the most popular theories.
Note: The content on Sleepopolis is meant to be informative in nature, but it shouldn’t be taken as medical advice, and it shouldn’t take the place of medical advice and supervision from a trained professional. If you feel you may be suffering from any sleep disorder or medical condition, please see your healthcare provider immediately.
Long Story Short
- There are many theories regarding why we yawn, but no general consensus has been reached as of yet about its function.
- Yawning frequently happens during the transitional time between being awake and being asleep which is why it’s often associated with sleepiness or boredom.
- Yawning can be a means to increase oxygen to the brain for the purpose of raising alertness.
- Excessive yawning can be associated with some neurological disorders as well.
Sleepiness and Boredom
That’s right: yawning tends to come over us when we’re making the transition from being awake to being asleep, or vice-versa, which is one reason it’s so often associated with being tired, or bored senseless. But while yawning often occurs when we are waking up, or nodding off, it may be associated with drowsiness and boredom in another way, too.
Yawning can be thought of as one method of increasing oxygen intake in times of low fatigue or boredom to maintain alertness and cognitive functionality, David tells Sleepopolis. Instead, it may be the way that the brain jump-starts our system rather than actually signaling we are drowsy or disengaged with what is happening. “This theory is saying you yawn when you’re feeling sleepy and need to increase alertness or ‘wake up’ the brain,” Purdy says.
As a Social Reaction
If you’ve ever yawned because someone else was yawning in front of you, or even read about it-in which case a few paragraphs back, it just might have occurred-you understand the concept of contagious yawning. This actually has been proven to be a documented phenomenon among humans, chimpanzees, and curiously, dogs. The “why,” on the other hand, is not very well explained.
One supposition is that contagious yawning represents some sort of empathetic social behavior that gives a communication signal of sorts, not unlike laughter.
A number of studies have suggested that the area of the brain implicated in contagious yawning also is involved in social understanding and social processing. Some studies have even concluded that the more empathetic, which is measured quantifying facial expressions, gestures, and then vocal responses, to certain situations presented, the more contagious yawning a person will experience. One such study even noted that women are more prone to this as well.
To Cool Down the Brain
Brain Cooling Another theory is that yawning deals with a mechanism of brain cooling. The idea here was that maybe, through a reflexive yawn, the brain causes cool air to be pulled into our system, thus lowering the temperature of the blood that actually circulates to the brain. “This cooling effect may improve mental alertness and overall performance,” says David.
Though some experts support this theory, it perhaps needs a little more investigation. Given that yawns are more likely when it is hot outside – which would have been exactly the right time for the brain to get a rush of cooling air in – it could actually raise the temperature of the brain if the surrounding air temperature is warmer than your blood. With this thought in mind, if this were the case, then when it is hot outside, yawns should occur less frequently because the other cooling mechanisms, such as sweating, kick in.
Other Theories
Some theories as to why we yawn run along the same vein as others, such as those concerning lung stretching and oxygen to the brain. “One theory is that when you yawn, you’re stretching the lungs and their tissues,” Purdy says. “This allows your body to also flex its muscles and joints. It may also increase blood flow toward your face and brain, which in turn increases alertness.
David also theorizes that yawning can be pivotal with the resets of our body’s respiratory mechanisms. “When we’re tired, our rate of breathing naturally becomes slow, and yawning serves as a form of stretching and exercising the muscles involved in breathing.” “It helps in enhancing ventilation and increasing oxygen levels in the body.”
Is There Such Thing as Too Much Yawning?
According to David, there is no general definition on the limit of yawning frequency. An average adult yawns about nine times in a day, and quite normally, too, two or three yawns in succession are considered normal (1). Excessive yawning, however is another story. “It may indicate underlying issues such as neurological conditions,” David explains. These include:
- Parkinson’s disease, epilepsy, and multiple sclerosis. Since these are brain conditions, they could cause excessive yawning, considered as more than three yawns within the span of 15 minutes without appropriate stimuli.
- Stroke.
It’s important to note that not all excessive yawning is alarming, as some simply have a higher baseline frequency,” says David. “But if someone experiences an unexplained increase in the frequency of yawning from one day to the next-especially in cases in which they don’t feel a need to sleep-it would be prudent to seek advice from a health professional for a thorough check-up.
That’s especially true if excessive yawning is becoming disruptive to your daily life, it interferes with your concentration, or you’re also experiencing other symptoms, such as sudden changes to your alertness.
Frequently Asked Questions
Why do we stretch when we yawn?
Why that may be, we always appear to be stretching when we yawn is something the researchers don’t understand yet. “One popular hypothesis is that stretching encourages blood flow to the brain and body, helping one to become alert,” David tells Sleepopolis. “It may also help in the redistribution of cerebrospinal fluid, which supports brain activity.”
Is yawning contagious?
It has also been observed during research that yawning is a contagious act, and this is not only restricted to humans, but also among primates and even dogs. While documented, we have yet to determine the exact cause of this. One theory is that contagious yawning constitutes empathetic social behavior operating as a type of communication signal, much like laughter.
The Last Word From Sleepopolis
While researchers continue to learn more about why we yawn, one thing is for sure: This reflex serves a greater purpose than simply stretching our jaw and making our eyes water-even if we don’t exactly understand it just yet.
While a yawn might be a minor thing, David says its role in maintaining our physiological equilibrium should not be underestimated.
Without yawning, our body would have a difficult time regulating its temperature and alertness, and we would be more fatigued with diminished cognitive performance and an overall decline in the physical and mental game, he says. That said, if you feel like you’re yawning too much, by all means, speak with your doctor.