Yawning does something unexpected to your brain: MRI scans reveal how yawning and deep breathing differ | Health - Hindustan Times
Yawning is an involuntary reflex action that is widely considered to be a sign of fatigue, boredom, or stress. However, a study published in the Respiratory Physiology & Neurobiology, titled Biomechanics of contagious yawning: Insights into cranio-cervical fluid dynamics and kinematic consistency, has revealed something unexpected about the effect of yawning on the flow of fluid that protects the brain.