There is no point in denying it, ‘Everybody yawns’! The yawn held practical value for the father of medicine, Hippocrates, the 5th Century BC physician who concluded that intense or prolonged yawning was a proof-positive symptom of an impending fever. He was incorrect. In fact, there is little evidence that the yawn has any diagnostic significance. However, some doctors believe that people with serious illnesses yawn less. In other words, yawning may be a sign of convalescence. Also, it is said that psychotic persons, ie. individuals who are out of touch with reality, rarely yawn. There is no proper explanation for this little piece of trivia.

Charles Darwin observed that baboons reveal hostility by yawning. He suggested that humans may do the same. But here also, there is no evidence to support this supposition. Imagine a romantic candlelight dinner for two. You and your date are enjoying each other’s company. It’s a perfect evening. All of a sudden, for no apparent reason, your date yawns. You can hardly believe your eyes and ears. You are mortified, hurt, angry and confused. How could your date find you boring?

Boredom was probably not the case. It could easily be that the slow service and hunger was the culprit. Perhaps the partner had a hard day at office and fatigue prompted the yawn. It could also have been due to a variety of reasons including indigestion or poor ventilation which may have triggered an involuntary yawn. Perhaps your partner saw someone else yawn and the copycat instinct took over. Or, if Darwin was correct, you would be wise to find out what you did wrong and apologise. In addition, if this is your first date, a yawn may be a signal of a person’s struggle to be attentive or to adapt to a new situation. People also occasionally yawn when leaving a movie, though the movie itself was not boring. Some research supports the fact that a yawn is necessary to re-adapt. As you leave the theatre, you yawn to readjust to reality.

What is a yawn? It is a complex, automatic, physiological experience whereby the lungs fully expand, heart generates greater activity and the blood receives more oxygen. The yawn begins with an involuntary spasm of the muscles of mastication and swallowing. It ends quietly with a sigh. You cannot subdue a yawn once it starts. So why do you yawn?  When you are exhausted, drowsy or fatigued, your breathing becomes shallow. Your rate of respiration slows down. If your breathing rate drops for an extended period of time and your activity level does not decrease, you are depriving your body of oxygen. Carbon dioxide, which under normal conditions would be exhaled, is now increasing in the body. As you breathe, you inhale oxygen, and exhale carbon dioxide. It’s actually the carbon dioxide in the blood stream which returns the respiration rate to its regular, normal level. Nerve cells, located in the respiratory center of the brain (in the brain stem just above the spinal cord), are most sensitive to the amount of carbon dioxide in the body. Where there is too much of it, the center signals the lungs to breathe deeper and faster. At the same time, the automatic nervous system forwards a message to the facial muscles around the jaw. Your muscles now contract, forcing you to yawn and to take an extra deep breath.

As a result, you take in an extra dose of oxygen and cleanse your system of excessive carbon dioxide. You’ll probably notice that you feel more relaxed and refreshed after yawning. This results not only from extra oxygen, but improved circulation when neck, chest and other muscles stretch and contract. A yawn therefore, is a boost to the body! So, yawn on!!