Yawn

 Adults typically do not yawn (or Oscitation), right before or after sleeping, during boring activities, and because of its infectious nature. It is often associated with anxiety, stress, fatigue and boredom. People are more likely to yawn when they see others yawning. It can be perceived as a person yawning or conversing with people who are looking at their phone and yawning. This is an scenario of feedback that is positive. The "contagious" behaviour of yawning may also be observed in cats, dogs and even birds. It is even observed in different species. About twenty psychological explanations for yawning have been suggested by scholars but there is little agreement on the importance of any one.During the yawning process, muscles that surround the airway are stretched, which includes chewing and swallowing muscles.Due to these movement of the muscles and breathing, the airway (lungs and throat) dilates to approximately three or four times its size. tensor tympani muscle in the middle ear contracts, which creates a rumbling noise thought to originate from the head, however the sound is caused by mechanical disruption of the hearing system and is not caused by the motion of air. In both mammals and humans, yawning can be caused by the instinctual desire to stretch several parts of the body, including shoulders, neck and back.