Aahh, the Science of Yawning

July 30, 2007 — -- It can signal tiredness, boredom or even rudeness, and everyone does it. But, now, a new science may explain why people yawn, and even crack one of the world's most mysterious phenomena — the contagious yawn.

Some people think yawning stems from a need to stretch or change. Until recently, scientists thought people yawned to replenish oxygen supplies to their blood.

But University at Albany psychology professor Gordon Gallup said, as people yawn, they cool off their brains.

"Brains are like computers," he said. "They only operate efficiently and effectively when they're cool. And, therefore, there are some very intricate cooling mechanisms that serve to regulate the temperature of the brain."

He said many things associated with yawning, like being tired, actually make the brain hot, and yawning can alleviate the heat.

"Extended periods of sleep deprivation raise brain temperature and do produce excessive yawning," Gallup said.

In a sense, the yawn is like the brain's air conditioner, which may make some rethink societal assumptions.

"Many people have the impression when talking to someone that if they yawn, it's an insult," Gallup said. "But according to our hypothesis, it's really a compliment, because it suggests that brain mechanisms have kicked in to reinstate and optimize mental processing."

Gallup and his son tested their idea by creating an experiment where students were asked to watch a film of other people yawning.