All hun1ans yawn. So do most vertebrate animals. Surely it serves some useful function. But what that might be has puzzled scientists throughout the ages. I Now a series of experrments suggests a surprising reason for yawning It cools the brain, says Andrew C. Gallup, PhD, a postdoctoral research associate at Princeton University We have collected data on rats, parakeets, and humans. All the data supports the brain-cooling hypothesis," Gallup says
Here's the basic idea:
When you start to yawn, powerful stretching of ther aw increases blood flow in the neck, face, and head The deep intake of breath during a yawn forces downward flow of spinal fluid and blood from the brain Cool air breathed into the mouth cools these fluids. Together these processes 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," Gallup says.
To answer skeptics, Gallup has laid out a more detailed anatomical description of the process in the n1edical literature.
We Yawn More When It's Cool
Gallup's theory predicts that colder outside air should cool the brain better than hot air The body should therefore yawn more when the air is cool, and yawn less when the air is hot. Nowhere is better to test this than 1n Tucson, Arizona. Gallup's team went the twice: Once in the winter, when it was a cool 71.6 degrees F outside, and once in early summer, when it was 98.6 degrees F
he researchers asked 80 pedestrians to look at pictures of people yawning. It's well known that people often yawn when see others yawn.Sure enough, in the cooler weather 45% of people yawned when they looked at the pictures. But in hotter weather, only 24% of people yawned. Moreover, people yawned more if they'd been outside longer in the cool weathe「, and yawned less if they'd been outside In the hot weather These results mimicked an earlier study in which Gallup's team showed that budgie parakeets yawned more in cool temperatures than they did in hot temperatures. And it supported a rat study in which rat brains cooled a bit when the animals yawned.
What We Say When We Yawn
Gallup says his brain cooling theory of yawning is the only theory that explains all these expeimental esults. But he has not yet convinced those who prefer another theory Physician Adrian G. Guggisberg agrees with Gallup that changes in room temperature can trigger yawning. But he's wary of the brain cooling theory. And he offers an alternative interpretation of Gallup's Tucson study. "The fact that yawning is suppressed during high terr1peratures suggest that it fails precisely when we need it," Guggisberg tells. "There are other ways to regulate body temperature， such as sweating, and it is unclear why we would need another regulator which fails when it matters." Yawn theorists split into two camps. Like Gallup, one side says yawning must have a physiological cause, and a physical benefit. The other side says yawning is a form of communication that offers various social benefits. Guggisberg prefers the social theory of yawning. He sees the physiological effects of yawning as too small to account for their persistence through evolution. But he sees the contagious effect of yawning as a kev clue
"The more people are susceptible to contagious yawning, the better their social corr,petence and empathy," Guggisberg says. "In humans it is clear that yawning has a social It is probably an unconscious behaviour. It is not clear what yawning communicates or what it achieves. But clearly it transmits some information that has some effect on brain networks or behaviour." Across cultures Guggisberg says, the yawn rs understood as a sign of sleepiness and boredom.The yawn thus corr1rr1unicates to others that one is experiencing a moderately unpleasant experience but not an immediate threat "We might have to used to the idea that yawns have a primarily social rather than primarily physiological effect," Guggisberg and colleagues wrote in a recent article Gallup argues that whatever message yawning communicates, it is far too ambiguous and subtle to be so wellconserved throughout evolutionary histor "It is not that I don't think there is any social function to yawning, because clearly it is contagious," Gallup says. "But we have to think of it as a process driven by physiological triggers we are unable to control. If it happens in a meeting, it should not be a sign of disrespect or insult."
Do the following statements agree with the information given in the Reading Passage? In boxes 1—10 on your answer sheet, write
TRUE FALSE NOT GIVEN if the statement agrees with the information if the statement contradicts the information if there is no information on this
1 All vertebrate animals yawn.
2 Yawning can encourage blood circulation in some parts of the body.
3 Yawning can keep your mind clear and active.
4 Yawning can infect even through watching pictures of people yawning.
5 The results of the study in animals are consistent with that of Gallup's Tucson study.
6 Sweating is more effective than yawning in cooling the brain.
7 The contagious effect of yawning indicates that it plays a physiological role.
8 It is a widespread idea that people yawn when they are bored or sleepy.
9 Gallup doesn't accept Guggisberg's idea at all.
10 According to Gallup, yawning in a meeting is an impolite behaviour.