Why Do We Yawn?
Does yawning mean you are tired or bored? It could be something else!
A yawn is an involuntary reflex where the mouth is opened wide, and the lungs take in a lot of air. The air is then exhaled slowly. During this time, the eardrums stretch, and the eyes may also close tight, causing them to water. No thought or action must be taken to produce a yawn, and the process is similar for everyone. Yawning commonly occurs either before or after sleep, which is why it is usually considered a sign of being tired. Yawning also occurs frequently in people who are doing boring or tedious things.
There is also a social aspect to yawning. Yawning appears to be contagious among humans and other animals, and the contagiousness of a yawn is well documented but hardly understood.
Fun Facts About Yawning
• Babies can yawn, even in the womb.
• Yawning is contagious, as part of human’s natural empathic response.
• Yawning serves a social function, communicating boredom.
• Yawning may be designed to help clear toxins out of the blood and provide a fresh supply of oxygen.
• Yawning may be designed to cool the brain; a yawn causes the jaw to stretch out, increasing blood flow in the face and neck.
What are the Potential Causes of Yawning?
There is no definitive reason for a yawn yet. Many proposed theories have surfaced and been studied, and they provide some clues.
A Change of State
Changes in state of being may be a possible cause for yawning. For example, when preparing to go to sleep or after waking up.
Yawning is commonly thought to be a sign of sleepiness or boredom, though this is not always the case.
While someone who yawns may be tired, the heart rate quickly rises during a yawn. This increased heart rate suggests yawning can be a sign of alertness rather than sluggishness. Yawning, in general, may simply be a way for the body to change the state of awareness it is in:
• Before bed: yawning could be taken as a sign that the body is preparing for sleep.
• When bored: yawning while doing a boring task may be a sign of the brain transitioning from a high level of alertness to a lower one.
• After exercise or sport: yawning after an intense sports activity may be a sign of transitioning from high energy to low energy in the brain.
People may also yawn when changing physical states as well, such as moving from an area of high pressure to low pressure. This pressure can build up in the eardrums and may cause the person to yawn to release it.
Yawning may be a function of breathing. Yawns may be more likely when the blood needs oxygen. A yawn causes a big intake of air and a faster heartbeat, which could theoretically mean that it is pumping more oxygen through the body. So a yawn may be simply designed to help clear toxins out of the blood and provide a fresh supply of oxygen.
Yawning may cool the brain; a yawn causes the jaw to stretch out, increasing blood flow in the face and neck. The large inhale and rapid heartbeat caused by the yawn also causes blood and spinal fluid to cycle through the body faster. This whole process may be a way to cool down a brain that has gotten too hot.
A study posted to Physiology & Behavior supported this theory. Researchers found that yawns were more likely at around 20 °C, which is the temperature they suggested would be ideal for cooling off the blood and brain.
Some researchers believe the reason humans yawn has more to do with evolution. Before humans communicated vocally, they may have used yawns to convey a message. Yawns are considered a sign of boredom or sleepiness, and that could be what early humans were communicating as well. However, early humans may have used yawning to signal their alertness to others, bare their teeth to aggressors, or serve as some other communication tool.
- Dr. Seevarathnam