When someone close to you yawns, do you have the same impulse, or subconsciously yawn In fact, yawning is contagious not only in humans, but also in other social animals, such as chimpanzees and lions. And it is possible that all vertebrates yawn spontaneously to regulate processes in the body
Andrew Gallup, an evolutionary biologist at the State University of New York Institute of technology, has been exploring the reasons behind yawning for many years. Recently, his research published in animal behavior shows through some evidence how infectious yawns evolved to protect us.
Gallup pointed out that other animals, like humans, yawn. This is a very complex reflex that can be triggered by various environmental and neurophysiological changes, such as the transition between sleep and wakefulness.
"Some studies have shown that yawning begins with the increase of excitability in the cerebral cortex. Therefore, yawning itself may help to improve the alertness of animals." Gallup said, "in addition, more and more studies have shown that increased brain temperature can also cause yawning. I have done a lot of research on humans, non-human mammals and even birds."
The above research conducted by Gallup shows that changing the ambient temperature, individual brain temperature and body temperature can effectively control the frequency of yawning.
"Our research in rats shows that increased brain temperature does cause yawning, and after yawning, brain temperature drops." Gallup said.
So why is yawning contagious?
Gallup pointed out that infectious yawning may have evolved into a group synchronous behavior, which usually occurs at a specific time of the day related to excessive state and activity. In addition, it may evolve into the behavior of increasing vigilance within the group.
"If yawning is a sign of a person's decreased alertness, seeing a person yawning may in turn increase the watcher's alertness to compensate for the yawner's low alertness. Therefore, the spread of infectious yawns in the whole group may increase the alertness of the whole group." Gallup said.
Gallup et al. They showed participants a series of images, including images of threatening snakes and frogs given non threatening stimuli, and calculated how quickly they could distinguish these images after seeing videos of people yawning or moving their mouths in other ways
"After seeing other people yawn, their ability to recognize and detect snakes, that is, their response to threatening stimuli, improved rapidly. However, after observing yawning, their ability to recognize and detect frogs was not affected." Gallup said.
Since yawning has many functions, are yawns of all animals contagious?
In this regard, Gallup said that spontaneous yawning is driven by internal physiology, while infectious yawning is caused by seeing or hearing yawning in others. This phenomenon is only recorded in highly socialized species, such as humans.
However, there are great differences in individual responses. Some people are easily affected by yawning, while others are not. Some studies suggest that this may be caused by the difference of empathy between individuals. However, other studies have failed to prove this relationship. The problem has not been settled yet and needs further study.