Your yawn may reveal how smart you are: Mammals with bigger and more complex brains gape for longer

Next time you try to stifle a yawn, it might be worth discarding polite etiquette by letting your mouth gape for as long as you need because it could help to reveal how smart you are. Biologists have discovered a surprising relationship between the length of time mammals yawn for and how big and complex their brains are. They believe it may also be a sign of greater cognitive ability. Yawning may give an indication of your cognitive abilities, according to a new study. The exact physiological function of yawning is still largely a mystery.