According to the latest research, vertebrates yawn in order to cool off their brain. Stress and tiredness most often lead to a rise in its temperature.
Scientists state that yawning is one of the most complex reflexes to study. Even though it appears to be the same every time, yawning occurs for different reasons and performs different functions.
Dr. Andrew Gallup from the State University of New York has performed experiments on rats, which have proven that yawning is caused by a rapid but slight change in brain temperature, by about 0.1 °C. The rats stopped yawning once the temperature normalized.
Stress and fatigue are the most common reasons for a rise in brain temperature, while yawning helps it to cool off. This completely disproves the theory that people yawn only when they are bored.
One of the most widespread theories about yawning is that it keeps the brain awake when we are under stress.
Yawning is also known for its contagious effect. In humans, as well as in animals, once one member of the group yawns, this gets passed on to the other members as well. According to scientific observations, this is a reflex for protecting the group.
The contagious effect of the yawn is also explained as a way of the other members of the group expressing empathy toward the yawner.
Studies done by scientists at the University of Maryland revealed that during a yawn, which lasts on average 6 seconds, complex chemical processes take place in the brain.
Gregory Collins, a researcher at the University of Texas Health Science Center at San Antonio, USA, has managed to identify several chemical processes that occur in the brain during yawning.
He explains that the most erroneous theory related to yawning, is that they are a way of supplying greater amounts of oxygen to the brain.
Among the established facts about yawning is that people tend to yawn more during the summer. Most people yawn when they see someone else doing it. Exceptions to this rule are infants, autistic persons and schizophrenics.
