From STAT News:
While every STAT story aims to stimulate your cortex, if this one falls short and makes you yawn, you can thank us anyway — at least if a study published Tuesday is right.
If you have a big brain, you can credit yawning for promoting brain growth and activity, the researchers found. And if you have a small brain, you can blame the fact that you don’t yawn long enough.
By “you,” psychologist Andrew Gallup of the State University of New York at Oneonta and his colleagues mean “your species.” In the paper in Biology Letters, they report that the average duration of yawns in 109 individuals from 19 species — from humans, African elephants, and walruses to mice, and rabbits, and capuchin monkeys — predicts a species’ brain weight and its number of cortical neurons.
While that may seem like just another bizarre correlation, it has at least some biological plausibility. In 2007 Gallup proposed what has become known as the thermoregulatory theory of yawning. It holds that opening our jaws and sucking in air cools the brain, something other labs have found support for. Yawning might also kick the brain out of its so-called default mode — a sort of background humming-along state — and into a paying-attention state by increasing the circulation of cerebrospinal fluid, a 2014 paper found.
Read the full story here.