Yawning is an involuntary intake of breath through a wide open mouth and is usually triggered by fatigue, boredom or whenever we feel sleepy. It can also be triggered when you watch another person yawn. This demonstrates to us, as humans, that we unconsciously and automatically are influenced by the behavior of others. Reading this article will even inspire you to yawn while reading about yawning!


So, after a hards day work on the job or a long boring one you will find your self yawning quite often while watching the clock or if you are a student, you may yawn from the fatigue of your study or from the boredom of the class and you might even yawn now and again while browsing the internet as you read and so on. However, for you to be reading this article up to this point shows you are curious and baffled by the mystery of the reason why we yawn. You may be surprised to know that you are not alone since the reason why we yawn is not completely understood. Thus, this article will look on the theories that explain the reason why we yawn.


Before we get into the theories we will quickly look at the part of the brain that makes us yawn. The part of the brain that make us yawn is the Reticular Formation which is a part of the brain stem that is found at the lower section of our brain (see diagram at left). The reticular formation is a region running through the middle of the hindbrain which leads into the midbrain. This part of the brain extends down into the spinal cord and contain sensory nerves that allow us to feel, touch and smell while the motor nerves allow us to move. The Reticular Formation function is to collect data input signals from other sections of the brain that control coordination (skeletal muscles) and pass on this data to the large cerebral cortex, where the information is processed and the necessary response is then executed such as us yawning. Here, certain sections of the brain "tell" your mouth muscles to move and stretch. Also, during yawning, the abdominal muscles and diaphragm also play an active role in the yawning process. When you yawn the diaphragm (see diagram) moves down to allow the lungs to expand causing air to enter. This is called inhalation. Conversely, when the diaphragm relaxes (moving up) the lungs contracts sending air out of the lungs. This process is called exhalation. These are all controlled by the motor cortex in the cerebrum and areas in the cerebellum of the brain. Thus, there are several parts of our brain that help in the yawning process which are controlled by several different regions of the brain. The reticular formation is also involved in sleeping, waking up and vomiting.

Here are three leading theories on why we yawn:

The Physiological Theory

This accepted theory states that when nerves in the brain stem find there's not enough oxygen in the lungs, we yawn by drawing in more oxygen rich air into the lungs followed by exhaling to remove the build up of carbon dioxide in our blood. If air sacs in the lungs don’t get enough oxygen then the tissue stiffen up a little causing the brain to respond by letting us yawn to get in more oxygen into the body. However, an expert on yawning Robert Provine, a psychologist at the University of Maryland, Baltimore County, tested this theory and found that getting more oxygen into our respiratory system or decreasing the amount of carbon dioxide from the environment didn't prevent yawning from happening.

Also, fetuses for instance, have been observed yawning in the womb, yet it is a known fact that they do not take oxygen in through their lungs.


The Boredom Theory

This theory states that yawning is caused by fatigue, boredom or drowsiness. This we can definitely relate to when listening to a boring speech, or when we feel tired and sleepy. Thus, displaying to others or as well as ourselves that we are either bored, tired or just feeling sleepy.


The Evolution Theory

This theory states that yawning originated with our ancestors who used yawning for displaying their teeth as a sign of intimidation and territoriality. As early man become more civilized, it lost its aggressiveness.

Conclusion:

Yawning is an involuntary response that have baffled humans for decades and even though we may have more knowledge through the advancement in science and technology, the mystery of why we yawn is still not completely solved yet. It is still not known exactly how a yawn occurs. The brain being the most sophisticated organ in our possession might be the key to this discovery. After all, the human brain has about 100 billion neurons which connect to thousands of other brain cells. Each playing their job in different regions of the brain through a huge network system.
Did you yawn while reading all of this? If you did, I hope it was not from boredom. I am yawning as this sentence is being written (YAWN).


Here Are Some Quick Did You Know Facts On Yawning:

• Reading about yawning will make you yawn.

• Yawning is contagious. Seeing someone yawning will make you yawn too, usually within five minutes.

• Most yawns occur during the hour before sleeping and the hour after waking.

• All animals yawn - fish, birds, snake, dogs, cats etc.

• Research has shown that at 11 week old fetuses yawn.

• The average duration of a yawn is about 6 seconds.

• The hypothalamus, a part of the brain, plays a role in yawning. Research has shown that some neurotransmitters (for example, dopamine, excitatory amino acids, nitric oxide) and neuropeptides increase yawning if injected in the hypothalamus of animals.
  

Here are some similar articles of interest and some sites with articles on yawing that you might also find interesting.
Why do people snore? | Why Do We Dream? | What causes hiccup?

| Scientific American | Neuroscience for Kids | Wikipedia |