Little research AFAIK was done why people or some animals, some fetuses yawn. One common observation once naay mo yawn is ang imong mga katupad naay chance mo yawn. It's involuntary. It is like someone is CONTROLLING YOU without you knowing.
If someone can break the code or find the missing link, it will change the world. So simple yet so powerful yet taken for granted ra kaayo ning pagpanguy'ab nato.
Use case: If I can induce VOLUNTARY yawn, then people around me will yawn. What if I induce something like closing my eyes using the principles of yawning? So people around me closes their eyes. It's dangerous.