Yawning regulates the temperature of the brain and helps cool it down, a recent study has revealed.
The new theory, proposed by Gary Hack, DDS of the University of Maryland School of Dentistry and Andrew Gallup, PhD of Princeton University, also insists that human sinuses play a pivotal role in this cooling process.
The researchers have argued that yawning does not occur because a person is tired, bored, or even in need oxygen, Newswise reported.
"The brain is exquisitely sensitive to temperature changes and therefore must be protected from overheating," the authors said.
"Brains, like computers, operate best when they are cool."
The scientists have proposed that the walls of the human maxillary sinus flex during yawning like a bellows, which in turn facilitates brain cooling.
The theory helps explain the function of the human sinuses, which is still debated among scientists. In fact, Hack says everything concerning the human sinuses is debated.
"Very little is understood about them, and little is agreed upon even by those who investigate them. Some scientists believe that they have no function at all," he said.
Beyond the physiological curiosity, the brain cooling theory of yawning also has practical medical implications.
Bouts of excessive yawning often precede the onset of seizures in epileptic patients, and predict the onset of pain in people with migraine headaches, said Gallup.
Hack and Gallup have predicted that excessive yawning could be used as a diagnostic tool in identifying dysfunction of temperature regulation. Excessive yawning appears to be symptomatic of conditions that increase brain and/or core temperature, such as central nervous system damage and sleep deprivation," says Gallup, a postdoctoral research associate at Princeton.
The study has been published in the journal Medical Hypotheses.