Why is yawning contagious?
According to one theory, this helps humans or other pack animals synchronize their schedules. Yawning is a signal to go to bed, thus, "infecting" each other with yawning, people or animals go to bed at about the same time. But this is just a theory, but statistics:
In fact, the percentage of people who start yawning when others do it ranges from 45 to 60% (chimpanzees react to people yawning only 33% of the time, and dogs - 72%!)
