Brain Cooling or Something Else? Scientists Still at Odds on Why People Yawn
The average human is thought to yawn about 250,000 times over the course of their lifetime, and babies in the womb reportedly start yawning from as early as 12-14 weeks.
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While yawning, a person opens their jaw wide, takes in a deep breath, and then quickly exhales, a common reflex which is also related to mammals, birds, reptiles, and fish.
Attempts to resolve the puzzle of yawning were made as long as 2,500 years ago, when renowned Greek physician Hippocrates suggested that this common reflex helps humans get rid of harmful air, especially when they have a fever.
"Like large volumes of steam escaping from cauldrons of boiling water, the air accumulated in the body comes out of the mouth when the body temperature rises", Hippocrates wrote at the time.
There is a popular present-day theory which asserts that yawning is a way to get more oxygen into the blood to increase alertness. Neuroscientist Robert Provine from the University of Maryland, however, insists that the theory doesn't hold water, pointing to the results of his experiments which showed that people continued to yawn when breathing air high in oxygen.
French family doctor Olivier Walusinski, for his part, asserts that when it comes to human beings, yawning is catching, which he claims is linked to empathy in humans.
Another theory, supported by Andrew Gallup of Princeton University, argues that yawning helps both humans and animals cool the brain in order to protect cerebral activity and increase efficiency.
He claims that the process of yawning "may act like a radiator, removing [too hot] blood from the brain while introducing cooler blood from the lungs and extremities, thereby cooling [brain] surfaces".
Some researchers, though, remain downbeat about Gallup's claims, pointing to the absence of conclusive proof and the fact that the researcher did not take direct measurements of the temperature of a human brain.
