A large-scale study of animals recently revealed that longer yawning means bigger brains. Specifically, what was unveiled was that vertebrates with larger brains and more neurons are said to have longer-lasting yawns.
The study authors gathered data on more than 1,200 separate yawns from both zoo trips and online videos, covering 55 mammal and 46 bird species in all, and discovered strong positive associations between how long an animal is yawning and its brain size.
According to Jorg Massen, an ethologist at Utrecht University in the Netherlands, they went to various zoos with a camera and there they waited for the animals to yawn.
A ScienceAlert report said this study could fill in some of the gaps about the common knowledge about yawning, which includes the reason it's happening first and foremost, and the reason animals like giraffes don't have the need to bother to yawn at all.
Longer Yawning, Bigger Brains
In their paper entitled "Brain size and neuron numbers drive differences in yawn duration across mammals and birds," published in Communications Biology, the researchers wrote, even though the "pattern of yawning is fixed," its length or how long it's happening has co-evolved with the size of the brain, as well as the numbers of neurons.
Furthermore, this function appears to be preserved across the different range of mammals, such that its evolutionary origin may be traced back to at least the typical ancestors of mammals and birds, and possibly, even further.
Such an assessment was set up to test a hypothesis from the study, "Yawning as a Brain Cooling Mechanism: Nasal Breathing and Forehead Cooling Diminish the Incidence of Contagious Yawning," published in the Evolutionary Psychology journal and presented in 2007 by one of the study authors who worked in this particular research, that yawning is an important way to cool down the brain. It consequently follows that bigger brains necessitate longer yawns for them to properly cool.
Such a conclusion would appear to be supported by this new data, which also reveals that mammals yawn longer compared to birds.
Yawns of Mammals
This report specified that birds have a higher core temperature compared to mammals. Meaning, a greater temperature difference that has surrounding air, which means a shorter yawn is adequate to drag in some air that's cooler.
The same conclusions were achieved in a study conducted in 2016 that involved humans, although in this case, only a little over 200 yawns and 24 species were measured.
Here, the researchers found that the shorter yawns at 0.8 seconds came from mice, with the longest yawns coming from humans at 6.5 seconds.
State University of New York ethologist Andrew Gallup explained, through the concurrent inhalation of cool air, as well as the stretching of the muscles that surround the oral cavities, yawning is increasing the flow of cooler blood to the brain and therefore has a thermoregulatory function.
In this particular study, the study authors did not make any association to intelligence, just the brain size and the number of neurons it has.
Neither the authors presented any reference to the frequency of yawning like if humans are inclined to yawn from five to 10 times each day.
Yawning is Contagious
The study also revealed that yawning is contagious, too as anyone might have noticed. One hypothesis for such an observation is that yawning serves as a social function, getting a group into a similar state of mind and probably, contributing to the synchronization of sleeping patterns.
The University of Vienna, Austria Biologist Margarita Hartlieb observed that capturing video footage of many yawning animals needs a lot of patience, and the subsequent coding of all the yawns has made her immune to the yawning's contagiousness.
A related report is shown on The New York Times' YouTube video below:
Read also: Discovering Sleep Behavior of Animals: Which are the Best Sleepers, and Which Ones Sleep the Least?
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