May 7, 2014
Why Do We Yawn? Study Claims To Have The ‘Cool’ Answer
Gerard LeBlond for www.redorbit.com - Your Universe Online
We commonly yawn when we are tired, before we go to sleep, when we first awake or when we're bored. The belief is that yawning increases oxygen to the brain, but previous studies have failed to link yawning and blood oxygen levels.
Brain temperature fluctuation is associated with sleep cycles, stress and cortical arousal, and yawning is a function of the body that stabilizes the temperature of the brain. By yawning, cooler air is taken in and replaces the warmer air lowering the brain temperature. The researchers believe the yawning only occurs during a thermal window, an “optimal range of temperatures.”
“Brains are like computers... They operate most efficiently when cool, and physical adaptations have evolved to allow maximum cooling of the brain. The thin posterior wall of the maxillary sinus may flex during yawning, operating like a bellows pump, actively ventilating the sinus system, and thus facilitating brain cooling. Such a powered ventilation system has not previously been described in humans, although an analogous system has been reported in birds,” Gallup said, as cited by Mercola.com.
Researchers believe that when you yawn blood flow increases to the neck, face and head, which forces a downward flow of spinal fluid and blood from the brain and the intake of cooler air cools these fluids.
“This is the first report to show that yawning frequency varies from season to season. The applications of this research are intriguing, not only in terms of basic physiological knowledge, but also for better understanding diseases and conditions, such as multiple sclerosis or epilepsy, that are accompanied by frequent yawning and thermoregulatory dysfunction. These results provide additional support for the view that excessive yawning may be used as a diagnostic tool for identifying instances of diminished thermoregulation,” the researchers explain.
Jorg Massen and Kim Dusch of the University of Vienna conducted an experiment with people in Vienna. They measured contagious yawning during both the summer and winter months and compared the findings with the same study done in Arizona. People were asked to view images of others yawning and they themselves reported yawning afterwards.
The study also showed that in Vienna, people tended to yawn more in the summer, but people from Arizona yawned more in the winter. This demonstrated that yawning was narrowed to an optimal thermal temperature range of around 68 degrees Fahrenheit, but diminished at a temperature of 98.6 degrees Fahrenheit.
Massen explained that yawning is not functional when the air temperature is the same as body temperature or higher, and that it is not necessary to yawn when temperatures are freezing, which could be harmful.
Most studies of contagious yawning have highlighted emotional and interpersonal variables, whereas this study emphasized both spontaneous and contagious yawning and brain temperature. Cooling of the brain serves to improve arousal and mental stability. The study also suggest that contagious yawning could enhance the vigilance of an overall group.