The Old Oxygen Theory
For many years, people believed that yawning was the body’s way of getting more oxygen to the brain. The idea made sense on the surface: you take a big breath when you yawn, so maybe your body needed extra air. However, scientists have tested this idea carefully and found it does not hold up. Studies showed that breathing different levels of oxygen and carbon dioxide did not change how often people yawned. If yawning were about getting more oxygen, breathing pure oxygen should stop yawning, but it does not. This discovery sent researchers looking for a better explanation.
The Brain Cooling Theory
The leading scientific theory today is that yawning helps cool the brain. In 2014, researcher Andrew Gallup published a study showing that yawning is more common in cooler temperatures and may help regulate brain temperature. When you yawn, the deep inhalation of cool air and the stretching of your jaw muscles increase blood flow to the brain, helping carry away excess heat. Studies have found that people yawn more in warm environments and less when they hold something cool against their forehead. This cooling effect may be especially important during transitions between sleep and wakefulness, when brain temperature naturally shifts.
When and Why We Yawn
Yawning is closely connected to changes in your brain’s state of alertness. You tend to yawn when you are becoming sleepy, when you are waking up, or during long periods of boredom and low stimulation. Athletes often yawn right before a big competition, and paratroopers have been reported to yawn before jumping out of planes. This suggests that yawning is not just about being tired but may help the brain shift into a more alert state when needed. Think of it as your brain’s reset button during transitions between different levels of activity.
Contagious Yawning
One of the most interesting things about yawning is that it is contagious. Just seeing someone yawn, hearing a yawn, or even reading about yawning can trigger you to yawn too. You might even be feeling the urge to yawn right now as you read this article. Contagious yawning is not limited to humans. Chimpanzees catch yawns from other chimps, and dogs have been shown to yawn in response to their owners yawning. Even watching a video of someone yawning can be enough to set off a chain reaction of yawns in a room full of people.
Yawning and Empathy
Scientists have found a strong link between contagious yawning and empathy, which is the ability to understand and share the feelings of others. Research shows that people who score higher on empathy tests are more likely to catch a yawn from someone else. Children typically develop contagious yawning around age 4 to 5, which is around the same time they begin developing stronger empathy skills. Studies have also found that you are more likely to catch a yawn from a close friend or family member than from a stranger. This connection suggests that contagious yawning may be rooted in the same brain systems that help us connect with other people.
Yawning in the Animal Kingdom
Yawning is widespread throughout the animal world, but different animals may yawn for different reasons. Many animals, including baboons, lions, and hippos, yawn to display their teeth as a warning or show of dominance. Guinea pigs yawn to show aggression toward rivals, while some penguins yawn as part of their mating displays. Fish, reptiles, and birds all yawn, suggesting that the behavior is extremely ancient. Scientists estimate that yawning evolved hundreds of millions of years ago, long before humans existed, making it one of the oldest behaviors we share with other animals.
Unsolved Mysteries of Yawning
Despite decades of research, yawning remains one of the great small mysteries of science. Scientists still do not fully understand why yawning is contagious or exactly what purpose it serves. Some people yawn more than others, and researchers are not entirely sure why. Excessive yawning, defined as yawning more than 3 times in 15 minutes, can sometimes be a sign of a medical condition and should be mentioned to a doctor. What we do know is that this simple, everyday action involves complex brain processes that scientists are still working to unravel.
OtterKnow Kids Encyclopedia