Why do you yawn even when you can NOT see/hear another person yawn?

Question

Why do you yawn even when you can NOT see/hear another person yawn?

Since the previous yawn thread was closed and no one seemed to answer the question above (all answers dealt with the visual/audio cues that yawns generate), I decided to ask the question but with a change.

Quite often, one can be riding in a car or sit in a room and yawn only to find a person out of view (or vice versa) follow up with a yawn. (no visual/audio cues).

Thanks.

Answer 1

Yawning is caused by lack of oxygen in the body, therefore, you are able to do this without seeing anyone else doing it.
I just yawned and no one is around............................

Answer 2

THE TRUTH IS that we don’t completely understand why people, or animals for that matter, yawn.

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.

http://www.coolquiz.com/trivia/explain/docs/yawn.asp

A yawn (synonyms chasma, pandiculation, oscitation from the Latin verb oscitare, to open the mouth wide) is a reflex of deep inhalation and exhalation associated with being tired, with a need to sleep, or from lack of stimulation. Pandiculation is the term for the act of stretching and yawning. Yawning is a powerful non-verbal message with several possible meanings, depending on the circumstances. It is also claimed to help increase the state of alertness of a person. It could possibly be from lack of oxygen. Another speculated reason for yawning is nervousness - paratroopers were once noted yawning right before their first jump. The exact causes of yawning are still undetermined.

A more recent hypothesis is that yawning is used for regulation of body temperature. Another hypothesis is that yawns are caused by the same chemicals (neurotransmitters) in the brain that affect emotions, mood, appetite and other phenomena. These chemicals include serotonin, dopamine, glutamic acid and nitric oxide. As more of these compounds are activated in the brain, the frequency of yawning increases. Conversely, a greater presence in the brain of opiate neurotransmitters such as endorphins reduces the frequency of yawning. Patients taking the serotonin reuptake inhibitor Paxil (Paroxetine HCl) or Citalopram, another SSRI, have been observed yawning abnormally often.

http://en.wikipedia.org/wiki/Yawn

Answer 3

ARGH!! I yawned reading your SENTANCE about yawning!

Answer 4

Maybe they're sleepy, bored or tired

Answer 5

they could be real tired o summit