Why yawn when you see someone yawn or hear about hi?

If someone yawns sitting next to us, we yawn, if someone yawns on the bus, train or road, others also yawn? If so, what hi choache? yawning is not contagious, so what is it ? yawning is very normal . Experts say that it is basically social behavior. Doctors say that this is  mainly due to the presence of mirror neurons in the body . Many times it is seen that hurting someone elose, if not physically, also causes emotional pain. In addition to humans, yawning occurs in chimpangees and dogs. Research showns that when a group of chimpanzees are shows yawning on video , they start yawning too. Research has referred to this as mirroring behavior. Researchers say that the mirror hormone responsible for hiatus is the only hormone present in the human body that causes this. Normally when we are tired the brain temperature rises. Yawning increases the blood flow to the brain , the brain becomes refreshed . we also try to be strengthened by imitating others .