The bigger the brain, the longer the yawn

 　　Do animals other than humans yawn too? The answer is obvious, yes! We are familiar with cats, dogs, rabbits, voles, hedgehogs, koalas and other small animals, as well as horses, tigers, lions and other large animals, all yawn. Snakes, turtles, iguanas, etc., among reptiles, as well as birds and even fish, all yawn. In conclusion, yawning behavior is present in all vertebrates.

　　There is a saying - the bigger the brain, the longer the yawn! is this real?

　　To confirm this claim, the researchers collected 1,291 separate pieces of yawning data from zoos and online videos, involving 55 mammal species and 46 bird species, and found that the animals yawned when they yawned and the size of their brains. There is a "strong positive correlation" between them.

　　After careful observation and statistical comparison of the duration of yawning in various animals, the researchers found that although the pattern of yawning is fixed, its duration is positively related to the size of the brain and the number of neurons. Furthermore, this function appears to be preserved in a wide variety of animals, so its evolutionary origins can be traced back at least to the common ancestor of birds and mammals, and possibly further.

　　Scientists have tested a previous hypothesis in research on yawning in animals: yawning is an important way to cool the brain. When the brain works continuously for a long time, it will heat up like a continuously running motor. After the heat, the working efficiency of the brain will be greatly reduced and fatigue will occur. And this tiredness triggers a protective mechanism called yawning -- which cools the brain by adding a lot of oxygen. As a result, larger brains require longer yawns to cool off.

　　Regarding the ability of yawning to cool the brain, Andrew Gallup, an ethicist at the State University of New York, also believes: "By simultaneously inhaling cold air and stretching the muscles around the mouth, yawning increases the flow of cold blood to the brain, so it has a temperature Moderating function."

　　This hypothesis is supported by more research data. Data shows that mammals yawn longer than birds. Birds have a higher core temperature than mammals, which means the temperature difference between the inside and outside of the bird's body is greater, so a short yawn is enough for the bird to inhale some cooler air.

　　Another group of scientists studied includes humans. The study observed 205 yawns and 24 species, including humans, and the data showed that the shortest yawn (0.8 seconds) came from mice and the longest yawns (6.5 seconds) came from humans. Among the animals involved in this study, the species with the smallest brain is the mouse, and the one with the largest brain is us humans.

　　The study also found that yawning in animals is also contagious. Maybe everyone has noticed this in our daily life: when a group of us are chatting, one person yawns, often causing others to have the same yawning behavior. Scientists have found that ostriches also yawn en masse before going to sleep: ostriches with higher social classes yawn first, signaling that there is no danger around them, and then the contagious yawn spreads among the rest of the ostriches. In response, scientists have hypothesized that yawning has a social function, bringing a group into the same mental state, perhaps helping to synchronize sleep patterns.