Almost all animals with a spine yawn. Penguins do it as a mating ritual; snakes do it to realign their jaws after a meal and guinea pigs do it to display anger. So why exactly do humans yawn? And is yawning actually contagious? If you haven't already checked out our yawn-o-meter video, click here or use the link in the description to see how long you can last before yawning.
几乎所有的有脊椎动物都会打哈欠。企鹅以此为求偶仪式，餐后蛇借此来整理下颌， 荷兰猪借此表达愤怒。那么人为什么要打哈欠呢？哈欠有传染性吗？如果你还没看过“哈欠耐力测试“这个视频，看看视频描述里的链接 看看你能坚持多久。
If you are anything like us, you may have even yawned at the title of this video. The truth is: the first time you yawned was likely as a fetus. Babies begin to yawn during the second trimester and though the reason why still unknown, it may have to do with proper brain development. In adults, yawns were commonly thought to draw more oxygen into the lungs making you feel less tired, but new researches states that this may not be the case.
Scientists now believe that yawning has developed a way of physiologically cooling your brain. Much like a computer, you brain work best at a certain temperature, and tries to avoid overheating. And it turns out, yawning increases your heart rate, blood flow and the use of muscles in your face, which are all essential to cool your brain.
On top of that, deeply inhaling cold air can alter the temperature of the blood in our head. But, why is your brain hot in the first place? Well, both exhaustion and sleep deprivation are known to increase overall brain temperature which explains why yawning occurs more in these states.
Researchers have even found participants who place warm packs on their heads yawn 41% of the time while watching others yawn, as opposed to 9% with a cold pack on their head. So if your head is already cold, you will yawn less. But what about contagious or social yawning? Humans, primates and even dogs finding yawning contagious and it's most likely linked to empathy. Contagious yawning begins in children around the age of 4-5,and this is when empathetic behavior, along with the ability to identifying emotions, begin to develop.
In fact, children with empathy related disorders, such as autism, yawn less and response to videos of people yawning comparing to other children .Research also suggest that you are more likely to copy the yawn of someone socially or genetically close to you. Even dogs are more likely to copy the yawns of their owner as opposed to the yawn of a stranger.
Finally, mirror neurons also play a role. In our brain, mirror neuron fire when we perform a specific action view someone else doing the action, or even just hear someone talk about the action. They are important brain cells that are used for learning, self-awareness and relating to others. When we view someone else yawn, the mirror neurons in our brain become activated in a similar way and as a result we copy the yawn.
So although yawning may occur in people who are literally hot-headed, contagious yawning allows us to be cool with the people around us.