Yawning doesn't mean you're bored, it just means you've got one big, hot brain in your head, according to a new study

Researcher Andrew Gallup had his students go online to collect videos of animals yawning. He then found that he was able to predict the yawn length of various animals based on their brain weight and the number of brain cells in their cortex. “We were just really blown out of the water,” Gallup said. “It’s such a strong predictor.” Perhaps surprisingly, body and mouth size had nothing to do with yawn length. The explanation for brain size correlating to yawn length comes from a theory first proposed by Gallup in 2007. He argues that animals yawn involuntarily to cool their brains. If that's true, it stands to reason that larger brains would require a larger yawn to cool. And it explains why humans' yawns, at 6.5 seconds, are the longest yawns in the animal kingdom, beating out those of gorillas, lions, elephants, and more. However, not all scientists are convinced yawning serves a cooling function, pointing to its contagiousness as evidence of a sociological function. Gallup isn't swayed. “Whether yawning functions specifically to cool the brain can still be debated, but there is no debate on whether yawning has thermoregulatory consequences," he says.