Everybody yawns. More than that, every animal with a spine yawns, too. And thanks to some dutiful research by yawn specialists, we now know more about yawns than ever. That is to say: Mammals with bigger and better brains have the longest yawns in the animal kingdom.
To determine this, the researchers had the amazing task of watching almost 200 animals yawn on YouTube, then timing their "full yawns" to the nearest 0.01 second. The 29 mammalian taxa in the study, which was published in Biology Letters, included 27 humans, along with an African elephant, 5 camels, 9 cats, 9 chimpanzees, a dozen dogs, 10 foxes, 6 gibbons, 13 rats, 6 mice, 7 lions, among others.
"As expected," the researchers wrote, "yawns from primates were significantly longer than from other mammals." We humans, the top primate on planet earth, are the yawn-time champs, posting average yawn times of just over six seconds. That's longer than both gorillas and chimpanzees, as well as non-primates of all shapes and sizes—mice, possum, cats, and dogs, you name it.
When it comes to the yawn game, here’s the top 10:
- African elephant
- White-fronted capuchin
At this point you’re surely wondering: Why do animals yawn anyway?
Years ago, yawnologist and neuroscientist Robert Provine found that we’re more likely to yawn when bored or tired (no surprise), as well as when we’re hungry. As Maria Konnikova wrote in the New Yorker, "Yawning may be, at its root, a mechanism of social signaling," a way of communicating with each other, mostly quietly, when we need a little help from our friends.
It’s a basic neurophysiological function: spontaneous and, as you know, sometimes contagious (even among chimpanzees). "Previous research suggests that yawning is an adaptation to enhance intracranial circulation and brain cooling, which in turn could promote cortical arousal and state change," the researchers say.
Yawning helps you wake up in the morning or stay awake during a conference all or get ready for a five-kilometer sprint, delivering much-needed glucose (brain fuel) and oxygen to the cerebral cortex, which governs, among many things, memory, attention, language, and even consciousness. The bigger and more complex the brain—not just weight but also encephalization quotient (basically intelligence or cognition), and cortical neuron number—the longer the yawn required to keep it humming just right.
So, next time you find yourself speaking in front of a yawning crowd, or group of friends, you could be offended or entertain the possibility that you're blowing their minds.