A yawn is a reflex consisting of the simultaneous inhalation of air and the stretching of the eardrums, followed by an exhalation of breath. It is commonly associated with tiredness, stress, sleepiness, or even boredom and hunger. This “contagious” yawning has also been observed in chimpanzees, dogs, cats, birds, and reptiles, and can occur across species. Approximately 20 psychological reasons for yawning have been proposed by scholars, but there is little agreement contagious why things catch on free pdf its main functions.
During a yawn, the tensor tympani muscle in the middle ear contracts, creating a rumbling noise from within the head. Yawning is sometimes accompanied, both in humans and animals, by an instinctive act of stretching several parts of the body, including arms, neck, shoulders and back. Latin hiō, hiatus, and Greek chasm, chaos.
Pandiculation is the act of yawning and stretching simultaneously. There are a number of theories that attempt to explain why humans and other animals yawn. It is likely that there are a number of triggers for the behavior. However, there are comparatively few theories that attempt to explain the primary evolutionary reason for the yawn.
Yawning may in fact reduce oxygen intake compared to normal respiration. However, neither providing more oxygen nor reducing carbon dioxide in air decreased yawning.