Yawning Scientific Facts: Why Do We Yawn and Is It Contagious?

What is yawning?

Usually, yawning is associated with boredom, fatigue, and tiredness. Yawning is also very common in animals, such as dogs, monkeys, snakes, and carnivores. Yawning is also associated with numerous superstitious beliefs.

In humans, yawning is considered as a purposeful non-verbal signal. Air rushes into your lungs from your mouth when you yawn. The lungs expand since the diaphragm is flattened. From the lungs into the blood vessels, oxygen is sent and carbon dioxide is exhaled. On an average, this entire process takes about six seconds. When a person yawns, it acts as a trigger, which induces yawning in other people as well. Within five minutes of seeing others yawning, around 55 percent of people would also yawn.

Among humans and other animals, yawning seems to be contagious, and although it is hardly understood, it is a well-documented phenomenon. To produce a yawn, no thought or action needs to be taken, and for everyone, the process is similar. Yawning usually occurs either before or after sleeping. Yawning is also commonly associated with tiredness, and in people who are doing tedious jobs. 

We yawn when it's cool

According to Dr. Andrew Gallup, a Princeton University research associate, yawning tends to cool the brain. Gallup says that their study has been conducted on humans, rats, and parakeets, and the results support the brain-cooling hypothesis. Thus, when the body is exposed to cool air, it induces more yawning. On the other hand, when exposed to hot air, lesser yawning is expected. 

Gallup and his team went to Tucson, Arizona twice to test this theory. They tested the theory in winter and in the early summer. The temperature during winter was 71.6 degrees Fahrenheit and 98.6 degrees Fahrenheit in the early summer. The team told people to look at pictures of yawning individuals. When people looked at the picture, 45 percent of them yawned in the cooler weather and only 24 percent yawned in the hotter weather. If people would remain in the cool weather, they tend to yawn more, and if they would be outside in the hot weather, they would yawn less.

There was an earlier study done, which showed that in cool temperatures, parakeets yawned more than in hot temperatures. The study that Gallup did mimic the earlier study. Also, this research supported a rat study. When the animals yawned, their brains cooled a bit.

When we say we yawn

According to Gallup, he has the only theory, which explains the results of the experiment. However, there are still some who are still unconvinced and prefer other theories. A physician from the University of Geneva, Dr. Adrian G. Guggisberg, says that yawning can indeed be induced when the body is exposed to room temperature changes. However, he is not completely convinced with Gallup’s theory. Instead, he provides a different explanation of the study done by Gallup’s team in Tucson. Guggisberg says that there are alternative methods when it comes to regulating body temperature. One way is through sweating.

Theorists regarding yawning are divided into two groups. One side believes that a physiological cause is a must for yawning to occur along with a certain physical benefit. The other side states that yawning is a means of communication, which provides a number of social benefits. The physiological theory of yawning is supported by Gallup, while the social theory is advocated by Guggisberg.

Guggisberg feels that people have better social competence and empathy if they are susceptible to contagious yawning. Although it has a social effect, yawning is still an unconscious act. It is not yet clear what is exactly communicated through yawning, and what is achieved, but certain information is transmitted, which can have some effects on one's behavior or brain network.

Guggisberg states that across cultures, yawning is considered as a sign of sleepiness or simply boredom. Thus, it can communicate that a person is having an experience that is moderately unpleasant. He feels that rather than a primarily physiological effect, yawning has a significant social effect. 

According to some researchers, yawning has more to do with evolution. To convey a message, humans must have used yawns instead of verbal communication. Early humans would likely communicate signs of sleepiness and boredom by yawning. However, they would also have used this sign to alert or show bare their teeth when they sense danger. Thus, yawning served as a communication tool.

A Change of State

Although yawning may indicate a sign of sleepiness or boredom, it is not always the case. A person who yawns may be tired. When a person yawns, the heart rate increases. Yawning may be suggested by this increased heart rate rather than being a sign of sluggishness. Thus, yawning can also signify alertness. Yawning may mean that the body has to change its state.

• Before bed - It could mean that the body wants to prepare itself for sleep.

• When bored - Yawning could indicate that the brain is transitioning from a higher level to a lower level. It may happen while doing a boring or dull task.

• After playing sports or exercise - Yawning may indicate a transition from high energy level to a low energy level in the brain. This may happen after an intense sports activity.

When people change their physical state, they may yawn such as when people go from high pressure to a low-pressure area. This pressure may build up in the eardrums and may make the person yawn.

Respiratory Function

When blood needs more oxygen, yawning may occur. Yawning causes the heart to beat faster along with a big intake of air. This could also theoretically mean that more oxygen is being pumped through the body. To get rid of toxins out of the blood, a simple yawn may help. 

Brain Cooling

The brain is cooled by yawning. When we yawn, we stretch our jaws, which causes the blood flow to increase in our face and neck. Yawning causes a large inhale and a rapid heartbeat, which causes the blood and spinal fluid to circulate faster. The brain that has gotten too hot can be cooled down by this process. It was found out by researchers that yawning is more likely to occur at around 20 degrees Celsius. The brain and blood can be cooled off at this temperature. 

According to scientists, yawning can be caused by the following reasons:

• Boredom - When people get bored, they yawn. When someone watches something amazing, they might not yawn, but students watching a boring video may yawn. 

• Sexual arousal - It is probably difficult to believe, but during sex, yawning may occur. Scientists say that it could mean that a person is sexually aroused since dopamine in the brain is produced. Scientists have experimented with erection-stimulating drugs, and then noticed that the common side effects were yawning and stretching. Yawning is often associated with a change in the state of the body, such as from a state of wakefulness to a state of sleepiness and not from a change of state from nonarousal to arousal.

• Showing of teeth - According to some experts, the showing of teeth was used by our ancestors to intimidate their enemy.

• To connect with others - Human yawning can be related to social factors. It may be done to express empathy. It has also been observed that contagious yawning does not seem to affect heavily autistic children. Other research also showed that we are less likely to yawn with strangers, but more likely to yawn with family and friends.

• This article may make you yawn - There is a very good chance that you may yawn while you are reading this article. Yawning may be triggered only by reading about it. Yawning is more likely to happen when a person sees a picture of someone yawning.

• To take in oxygen - This theory was accepted for a while. We give ourselves an oxygen boost by breathing deep into our lungs. At the same time, we get rid of carbon dioxide out of our blood. However, according to neuroscientist Dr. Robert Provine, if extra oxygen were given to people, there would be no significant decrease in the frequency of yawning. Moreover, decreasing the level of carbon dioxide in their environment cannot prevent yawning.

• Sleepiness - You may yawn because you are simply sleepy. Researchers found that in the hours before sleep, people yawn more frequently than during the hours after waking up. Earlier in the day, young adults yawn more frequently. After being awake for just one hour, they may yawn.

• Serious medical condition - The first symptom of vasovagal reaction could be yawning. Other symptoms associated with it are lightheadedness, nausea, and cold sweat. Excessive yawning can also be a sign of a heart attack. Frequent yawning may also be observed in people with sleep disorders such as hypersomnia and narcolepsy. It might be a good idea to visit a doctor if you feel that you are yawning too much.

In Animals

Not just humans and chimpanzees, but all vertebrate mammals tend to yawn. However, contagious yawning is only found in humans, the family of dogs or wolves, and chimpanzees. 

Causes of Yawning

• When the level of glucose supplied to the brain is reduced, yawning may be induced. This can be in the state of hunger. In fact, hypoglycemia is associated with excess yawning. This condition occurs when the glucose level in the blood is low.

• To maintain proper lung inflation, the body has adopted a protective reflex mechanism, and according to some researchers, yawning is a part of that mechanism. By yawning, the alveoli is prevented from collapsing. Pressure on the lungs increases when a person slouches for a long time, and to compensate this, the person may excessively yawn. 

• According to another study, there are several substances that can induce yawning. These substances tend to activate oxytocinergic neurons in the brain, which leads to yawning. 

Although there are many theories and suggestions about yawning, no single reason has been validated yet as to why we yawn. The most acceptable reason could be the chemical facilitation of yawning. To pinpoint the exact reason for yawning, more studies are still needed.