What makes a yawn s refreshing? It's not the oxygen. But the secret may still lie in the blood: yawning routes an extra helping of blood to the brain. What the blood does once it's there is anyone's guess, but Ronals Beanninger, a psychologist at Temple University in Philadelphia, believes that it helps to perk vs up. In support of this theory, researchers have found that people also yawn when they are suflering from a haemorrhage or motion sickness, both of which tend to decrease the amount of blood available to the brain