Yawning is as common as it is mysterious: even though just about every animal with a backbone does it, we don’t really know why.
A new study from the State University of New York has turned up some strange new details about yawning, finding that animals with bigger brains have longer yawns.
Led by psychologist Andrew Gallup, the research team discovered this in the most scientific way possible: by timing YouTube videos of yawning animals, including cats, dogs, chimps, elephants, hedgehogs and — of course — humans.
The 29 animals in the study were chosen because of their inclusion in a 2005 study that precisely documented the weights of their brains and the number of neurons in their cortexes — the outer layer of the brain that processes the most information.
Heavy-brained humans had the longest yawns, while pinheaded mice and rats had the shortest. In general, primates had longer yawns than other mammals, lasting about 4.5 seconds on average.
In the full paper, the researchers write that their finding supports the idea that yawning has some important “neurophysiological function” — most likely to enhance blood flow inside your skull or to regulate brain temperature.
Animals with more complex brains might need longer yawns to “to more effectively modulate cortical arousal”, that is, which parts of the brain get switched on (and not sexual arousal, which is what everyday folks usually mean by that word).
Yawning is legendarily contagious — so contagious that even reading this article about yawning might trigger a yawn — but the researchers aren’t sure what their finding indicates about the possible social or communicative function of yawns.
They concluded that further research on yawning is needed, and that it should take into account the duration of yawning.
The paper quoted neuroscientist Robert Provine, who observed that “yawning may have the dubious distinction of being the least understood, common, human behaviour”.
FYI, Provine is the mad scientist who, in his research on yawning, attempted to produce a “doomsday yawn” — the perfect set of triggers that could induce a yawn 100 percent of the time. (It didn’t work, thankfully.)