You likely know the feeling of a yawn coming on. Seemingly outside of your control, your mouth opens wide, your jaw drops, and you inhale deeply through your mouth and nose, followed by a shorter exhale. Maybe you stretch out your arms and legs and close your eyes tightly as your yawn peaks.
You may notice yawns coming on when you’re tired or bored, or even when you see another person or animal yawn. But why exactly do we yawn, and what makes yawns contagious? Read on to learn more about this shared human experience that continues to perplex scientists.
Why Do We Yawn?
Considering that the average person yawns 20 times per day, the reasons why we yawn are surprisingly mysterious. Despite years of research, scientists can only pose theories based on what happens to the body during a yawn.
The Science of Yawning
Spontaneous yawning, or yawning that arises internally, is brought on by the hypothalamus in the brain. The hypothalamus responds to certain stimuli and triggers muscles in the face, throat and chest to initiate a yawn. So, what stimuli cause the hypothalamus to trigger this reaction?
Causes of Yawning
For years, the prevailing theory was that we yawn when we need more oxygen. However, researchers have disproved this long-standing theory in recent years because the mechanisms that control breathing and yawning are separate.
According to the Cleveland Clinic, the three most popular current theories as to why we yawn are that it wakes us up, relieves ear pressure and cools the brain.
Sleepiness
One of the most common times we yawn is when we are tired. Andrew Gallup, an evolutionary biologist and yawn-research expert at the State University of New York Polytechnic Institute, explains that yawns can actually help to make us more alert and awake.
When we yawn, our face and neck muscles move, increasing blood flow to the head and brain and likely stimulating the carotid artery. This increases our heart rate and triggers the release of hormones that promote wakefulness. So, when we yawn due to drowsiness, our bodies are likely trying to wake us up.
Boredom
Yawning is also a common reaction to boredom or disinterest. We likely yawn when bored for much the same reason as when we’re tired–to increase alertness. A sudden uptick in heart rate and blood flow to the brain may help us refocus on the task at hand.
Ear Pressure
Another possible reason for yawning is that it helps to equalize the pressure in the Eustachian tubes, which connect the middle ear to the back of the throat. It is helpful to yawn when rapidly changing altitude, like when flying in an airplane or taking a fast-moving elevator. Yawning allows air to flow and balance the pressure around the eardrum.
However, while ear pressure does indeed equalize when yawning, this does not account for the majority of yawns, which occur while we are not changing altitude.
To Cool the Brain
A leading theory is that we yawn to cool the brain. Yawning increases blood pressure and facial and cerebral blood flow, both of which help cool down the brain.
Research supports this theory. Participants in a study by Andrew Gallup yawned significantly less when using brain-cooling techniques, including nose breathing and applying an ice pack to the forehead, than did those whose brains were either heated up via a hot pack on their foreheads or left at room temperature.
What Makes Yawns Contagious?
If you notice yourself needing to yawn whenever someone near you yawns, you’re not alone. In fact, research has shown time and again that yawns are contagious.
When researching yawns, Gallup divides them into spontaneous yawns and contagious yawns. The latter consists of yawns brought on by seeing another person or animal yawn rather than by any internal state like drowsiness. Many scientists believe that yawning serves a psychosocial function, which provides the basis for contagious yawning.
What exactly makes yawns contagious is a topic of great interest to Gallup, who published a study in 2022 that examined humans’ reactions to yawns in other humans and a variety of non-human species.
Is Contagious Yawning A Measure Of Empathy?
While a long-standing theory was that yawns are contagious because we yawn out of empathy, Gallup’s recent research does not indicate a correlation between empathy and contagious yawning.
Group behaviors around yawning in various species indicate that synchronized group behavior is a more likely reason. Because yawning wakes up the body, stirring it from drowsiness, it is thought that when one member of a group yawns, it triggers other members to increase their own alertness to make up for their drowsy companion. As a yawn passes around a group, the overall alertness of group members increases.
Can A Person Yawn Too Much?
Yawning is not bad for you, so there is no need to worry about frequent yawning causing health issues. However, excessive yawning could potentially indicate underlying health problems.
What Is Excessive Yawning?
The average number of yawns per day is 20, so unless you are yawning quite a bit more than that, there is likely no cause for concern. The main thing to watch out for is a marked increase in the amount you yawn. For instance, if you usually only yawn a few times a day and are now yawning seemingly all the time, you should talk to your doctor.
According to the Cleveland Clinic, some health problems that could cause an increase in yawning include:
- Migraines
- Stroke
- Epilepsy
- Parkinson’s disease
- Multiple sclerosis
Even if your frequent yawning isn’t due to a serious illness, it could indicate that you are not sleeping enough or are getting poor sleep. If you suspect your sleep could use some work, try implementing sleep hygiene tips to get better sleep.
Can You Withstand The Yawn Test?
Some people are more susceptible than others to contagious yawning. While researchers cannot say with certainty why that is the case, it is interesting to note that some people are greatly affected by the yawns of other humans and even animals, while others are not.
To see how you stack up, watch the video below. In a study by Duke University, 328 subjects watched this video, and only 222 contagiously yawned. Among those who yawned, the total number of yawns varied between one and 20. This study challenged the idea that contagious yawning relates to empathy, as age was the only statistically significant factor noted by researchers (and even that only accounted for 8% of the variability in yawn response).
How long do you think you’ll last compared to other participants?
What Does It All Mean?
Even though scientists like Gallup are making massive strides toward better understanding why we yawn and what causes contagious yawning, much remains unknown. Spontaneous yawning serves various physiological purposes, while contagious yawning may confer social benefits. Further research is needed for us to fully understand the complex reasons for this simple process.
FAQs
Why do we yawn when we see someone else yawn?
The exact reason for contagious yawning is not yet fully understood. Recent research indicates that it likely relates to synchronized group behavior, while the long-standing theory that it relates to empathy is not supported by research.
Is yawning good for you?
Yawning provides physiological benefits, including increased alertness, equalizing the eustachian tubes in the ears and cooling the brain. It may also provide social benefits, such as bonding. Excessive yawning, however, could indicate an underlying medical condition.
Is it scientifically proven that yawns are contagious?
Yes, scientists have proven through various studies that yawns are contagious across multiple social species. Some humans yawn not only when they witness other humans yawning, but also when they see cats, dogs, gorillas and even reptiles and fish yawning.
Why do we yawn when we’re not tired?
Physiological causes for yawning outside of drowsiness include boredom, ear pressure and the need to cool the brain. There are also psychosocial reasons for yawning, including social bonding and increasing group alertness.