Need a Boost? Yawning Helps : Behavior: Birds do it. Hippos do it. Even fish yawn, and a few scientists are trying to find out why people do it.
Reading this article is likely to increase your mental alertness. Or so one could conclude from a leading theory on why people yawn.
Everybody knows that yawning is contagious. Seeing another person yawn can trigger the effect in many people. It begins with that familiar tightening in the neck just under the jaw and swells into a mouth-widening, chest-swelling inhalation and, finally, a satisfying exhalation.
And, as many people notice, a little bit of a rush follows, a brief sharpening of the senses.
That head-clearing effect, according to Ronald Baenninger, one of the few scientists in the world to study yawning, is the best guess as to why we yawn. It is a way of increasing mental alertness.
He notes, for example, that yawning is most common just after people wake up and late at night when they’re trying to stay awake. Once people “give themselves permission to fall asleep at night,” he said, yawning ceases.
“As everybody knows, people also yawn a lot when they’re bored,” said Baenninger, who teaches psychology at Philadelphia’s Temple University. “Classrooms and lecture halls are the absolute best places to observe yawning.”
Baenninger sees these as instances in which subconscious mechanisms in people’s brains are trying to get them awake and alert or to keep them that way. Nobody knows exactly what the mechanism might be. Some suggest that the mechanics of yawning improve drainage of blood from the brain, allowing a brief surge of fresh, oxygenated blood to enter. Others suspect the act may trigger the brain’s production of stimulatory neurotransmitters, substances that relay signals from one cell to another.
“It’s not just people, either,” he said. “All kinds of animals yawn. Birds yawn. Even fish yawn. For a behavior to be that widespread, it has to have a real purpose.”
Baenninger said many animals yawn at the same times that people do. Lions in the wild yawn in the early evening as they are getting up from their daytime napping to prepare to hunt. Observation at the Philadelphia zoo shows that captive lions yawn most just before feeding time. “They’re getting up for it,” he said, “the same as if they were going to hunt.”
Mandrills, other baboons and laboratory rats also yawn a lot just before feeding time. So do damselfish and “Siamese” fighting fish, gulls, ostriches, rhinoceroses and hippopotamuses.
People who live with cats and dogs, Baenninger said, may notice the same things. Dogs are known to yawn--and to stretch, an activity that can accompany yawning in many species--just as the regular time for their walk approaches.
The only non-yawning vertebrate species Baenninger has found is the giraffe. One of his graduate students spent 35 hours watching zoo giraffes and never saw a yawn. Because of the great distance between the head and both heart and lungs, giraffes have special adaptations for breathing and blood circulation that Baenninger speculates may obviate the need for yawning.
In all yawning species, the form of the event is consistent: The mouth opens slowly and then, after the peak, it shuts quickly. Even the duration is consistent--five to six seconds.
Baenninger said the alertness theory fits well with observations of human yawning, a type of research that has not been easy to do.
“The usual funding mechanisms of science don’t take this stuff seriously,” Baenninger said. “Even I started this work almost as a joke, but it has turned out to be so fascinating that I keep it up.”
Yawning is so neglected by the scientific Establishment that pharmacologist Alan Cowan had been studying the phenomenon for years at Temple before he learned that Baenninger shared his interest. The two researchers constitute what may be the nation’s leading yawning research center.
Cowan said there has never been a scientific conference on the subject. “There was a three-day international conference on scratching and grooming at the New York Academy of Sciences a few years ago, and a hundred scientists came,” Cowan recalled. “Yawning has never been taken that seriously.”
The research has also been difficult, Baenninger said, because “when you bring people into the lab, they steadfastly refuse to yawn. They’re probably anxious, and this could mean they don’t really need to yawn to keep alert.” But when volunteers are put in a room where they think they can’t be seen--and are observed through a one-way window--they yawn just as predicted.
Cowan said that yawning can be induced in animals by giving them substances known to alter interactions among neurons and neurotransmitters. For example, dopamine and other substances that bind to dopamine receptors induce yawning. This fits with the observation that people with Parkinson’s disease, in which the brain loses its ability to make dopamine, rarely yawn.
“We used to think dopamine was the story,” Cowan said, “but we know now that many other things induce yawning and they act in different ways. We know less now than we thought we did a few years ago.”
Even less clear is why yawning is contagious. Baenninger speculates that this evolved as a way of synchronizing the arousal states of all members of a social group. “When the leader of a primate group gets up in the morning and yawns,” he said, “that gets the others going. It might be important to do this so that they can all be ready to move together.”
