Yawning
Yawning is an intense contraction of the muscles of the face and diaphragm resulting in a deep inhalation of air through the opening of the mouth, followed by a short exhalation. It is a reflex behavior, phylogenetically old, stereotyped but modulable and physiologically contemporary of muscular stretching. It is often associated with the need for sleep, anxiety, hunger, sexuality or boredom. It is present in all vertebrates, including all mammals, including humans, reptiles, fish, and birds. Yawning is a commonplace physiological behavior, described in antiquity by Hippocrates who thought in his Treatise of the Winds that yawning allowed the evacuation of fever, like a chimney evacuates the smoke. Other Roman doctors linked high infant mortality with the fact that babies yawned a lot, while Hindus believed that during the ...