Today, there are many theories about the contagiousness of yawning, as this issue has interested mankind since ancient times. Interestingly, yawning lasts 6 seconds with an average frequency of every 68 seconds.

 According to the English scientist Malcolm Weller, the contagiousness of yawning is associated with human evolution, where yawning was a sign for animals that it was time to return for the night. 

The American scientist Ronald Benninger also agrees with this theory, adding that our ancestors synchronized their rest and activity with yawning. An experiment was also conducted among students, which consisted of watching videos of people yawning for the same period. As a result, it was concluded that only students with the most significant ability to empathize with their neighbors yawned.

Magnetic resonance tomography showed that these students had high activity in the areas of the brain responsible for empathy. Therefore, studies have shown that viewing photos or videos of yawning can provoke the contagion of yawning.

Researchers at Duke University have found that the contagion of yawning may decrease as people age. For example, people with autism or schizophrenia are not susceptible to yawning contagion, and the same can be said for children under four. 

Scientists proved that humans, chimpanzees, and some species of monkeys are exposed to yawning contagion, and all other animals, even fish, yawn without realizing it. Another interesting fact is that strangers will not yawn when they look at someone.