When I'm hungry and tired (low level of blood sugar)

Yawning is an intake of air to try and speed more oxygen to the brain, usually because you are tired or not getting enough oxygen


it is contagious, but only in a "sympathetic" sense, IE, you dont catch it like a virus or disease, its sorta like when you hear running water and it stimulates your body to have to use the restroom

It’s widely assumed that yawning occurs because we are tired or bored or because we see someone else doing it, but there isn’t any hard evidence to support these beliefs.

Scientists do not purport to know all of the biological mechanisms of the yawn, but tend to agree that a yawn is an involuntary respiratory reflex, which regulates the carbon dioxide and oxygen levels in the blood.

Technically, a yawn is the reflex opening of the mouth followed by the deep inhalation and slow exhalation of oxygen.

The very act of yawning is but one of a number of involuntary reflexes controlled by the spinal and nerve centers.

Scientists speculate that the onset of a yawn is triggered either by fatigue, or by sheer boredom as, at those times, breathing is shallow, and little oxygen is carried to the lungs by the oxygen-toting cardiovascular system.

When one yawns, his or her alertness is heightened, as the sudden intake of oxygen increases the heart rate, rids the lungs and the bloodstream of the carbon dioxide buildup, and forces oxygen through blood vessels in the brain, while restoring normal breathing and ventilating the lungs.

Ok this isn't a joke, I was posting in another thread and as soon as I read this one I yawned.

idk but when i saw the topic title i yawned

Vouch ^^

if i had a nickel for every time i've seen someone butcher the word definitely, i'd have 2 dollars

i believe yawning is caused by irregular nitrogen levels in the brain. no one really knows for sure tho.

When reading threads like these?

win