Yawning Kittens

A yawn (from the Middle English yanen, an alteration of yonen or yenen, which in turn comes from the Old English geonian), is a reflex of simultaneous inhalation of air and stretching of the eardrums, followed by exhalation of breath. Pandiculation is the act of stretching and yawning simultaneously.
Yawning is associated with tiredness, stress, overwork, lack of stimulation, and boredom. Yawning can also be a powerful non-verbal message with several possible meanings, depending on the circumstances. In humans, yawning has an infectious quality (i.e., seeing a person yawning, talking to someone on the phone who is yawning, or just thinking of yawning can trigger yawning) which is a typical example of positive feedback. Infectious yawning has also been noted in chimpanzees.
There are a number of theories that attempt to explain why animals yawn. It is likely that there are a number of triggers—not just one—for the behavior. However, there are a few select theories that attempt to explain the primary evolutionary reason for the yawn. None of them has been empirically substantiated. The first states that yawning occurs when one's blood contains increased amounts of carbon dioxide and, therefore, becomes in need of the influx of oxygen that a yawn can provide. Researchers believed this theory to be true at least since Hippocrates, but studies have since shown it to be either incorrect or, at the very best, flawed. Yawning may, in fact, reduce oxygen intake compared to normal respiration, not increase it.