Far and wide around the world, a whole bunch of animals are yawning right now. Maybe they’re ready for bed; maybe because they are hot and bored.
But if one thing is certain, the very thought of yawning makes us want to open our mouths and take a deep breath for some reason. (I’ve already muffled a few yawns, and I’ve barely entered the paragraph.)
While scientists are quite confident that they understand the physiological purpose of yawning, the reasons why it is so contagious among social animals are still unclear.
As is often the case in science, the answers could already be scattered throughout the literature we have collected on animal neurology, psychology, and social behavior.
To determine what the existing evidence on the subject says, evolutionary biologist Andrew Gallup of the New York State University Polytechnic Institute searched past research and compiled the results into a single model of explanation.
According to Gallup, yawning could be a way for groups of animals to synchronize their behavior and promote collective vigilance.
Together with that other strange reflex of panting, hiccups, yawning seem to have no obvious purpose. In moments of calm (usually when we are tired), the jaw muscles contract, the diaphragm bends strongly and we breathe cold, clean air for a long time.
It used to be speculated that it was a means of supplementing oxygen or rejecting carbon dioxide, but now it seems to be more about alleviating blood temperature in an effort to cool the brain.
This means of thermoregulation must be important - it does practically everything that has a spine. From mice to monkeys, fish to flamingos, yawning is a function that probably developed a long time ago in our common ancestors.
If so, why would one good yawn deserve another? Initiating consecutive yawns between individuals - a behavior so contagious that it can cross species barriers - would insinuate a benefit to a group of brains that are all cooling off together.
This may not be far from the goal. According to Gallup, that benefit is a literal wake-up call that helps compensate for the drowsiness of individuals.
Yawning generally occurs as we move from one state of activity to another, whether you lie down to rest or wake up after a long sleep. We also yawn when anticipating change, causing sparks, or maintaining excitement when the environment is unlikely to be stimulating.
A quick ‘brain cooling’ from that influx of fresh air could be the perfect way to shake it up briefly in preparation for a possible task without running it into a fight or flight mode.
In this light, it may not hurt if a few friends take care of your back while drowning or falling asleep in a potentially hairy situation. By sharing that yawn around, a group of brains can calm down, raising alert while one or more members of the group show signs of change.
In a conversation with Tess Joosse on Science magazineGallup recalls an experiment he conducted last year.
“We showed people a series of images that included threatening stimuli - snake images - and non-threatening stimuli - frog images - and determined how quickly they could choose those images after seeing videos of people yawning or moving their mouths in other ways,” Gallup explained.
“After seeing other people yawn, their ability to identify and detect snakes, a threatening stimulus, quickly improved. However, after watching the yawn, the discovery of the frog did not affect that. “
As for the model of explanation, it is a convincing idea that is ripe for experimentation. Revealing the secrets of good yawning could tell us something about subtle forms of communication within and between social species, including our own.
This research was published in Animal behavior.