People yawn when others yawn due to a phenomenon called "contagious yawning," which is linked to social bonding and empathy. This reflex starts around the age of 4 or 5, when children develop empathy, the ability to understand and share the feelings of others. Seeing someone yawn activates mirror neurons in the brain, which cause a person to unconsciously imitate that action, fostering social connection. Contagious yawning is stronger among people who share a close bond, such as friends or family, and is also seen in some animals like chimpanzees and dogs. The behavior may serve to synchronize group vigilance or social behavior and is not purely due to physiological causes like brain oxygenation.
In summary:
- Contagious yawning is a reflex linked to empathy and social bonding.
- It involves activation of mirror neurons that mirror observed behavior.
- It is more likely between people with strong social connections.
- The behavior may help synchronize vigilance or alertness in groups.
This explains why seeing someone yawn triggers an automatic urge to yawn as well.
