We’ve all been there: it’s about half an hour after lunch, your sandwich has just about hit your belly, and 5pm is looking an awfully long way off.

Cue the yawn.

via GIPHY

The yawn is so much more than a signal of how tired we are. It’s also a symptom of boredom, an expression of rebellion, a facial workout, and an utterly contagious bodily function – there’s a reason one yawn triggers another, you know.

However it seems as if there’s even more to our yawns than we first realised.

Read more: This common everyday reaction could signify whether you’re a psychopath or not

A new study has revealed that the length of your yawn matches the weight of your brain, and, therefore, how many neurons it has.

Or, to put it in layman’s terms for all the short-length yawners out there, the longer your yawns last, the more intelligent you are.

The research team found that the animals with bigger brains were more variable in the length of their yawns.

Liz Cirulli Rogers, from Duke University School of Medicine, said it is possible that more intelligent animals have different types of yawn in response to different stimuli while the less-intelligent ones only have one type of yawn.

“Using openly accessible data, we show that both the mean and variance in yawn duration are robust predictors of mammalian brain weight and cortical neuron number,” the researchers wrote in their study, which was published in Biology Letters.

“Consistent with these effects, primates tend to have longer and more variable yawn durations compared with other mammals.”

Read more: The worst mistake you can make in a work email, according to business experts

Speaking to Academic Minute, lead researcher Andrew Gallup went on to explain that we yawn to decrease our brain’s temperature when it’s enjoyed a particularly vigorous workout (e.g. during an exam, whilst partaking in a crossword, or while trying to process new information / stay awake through that big presentation).

“When you yawn, your gaping jaw increases circulation to your skull, pumping warm blood out of your brain,” he says.

“At the same time, inhaling deeply brings a wave of air into your nasal and oral cavities, cooling cranial arteries through convection.

“These two processes dissipate heat in much the same way that a radiator cools a car engine."

So there we have it: next time someone yawns midway through your story about your nosy neighbour, don’t berate them. Instead, take solace in the fact that your tale is giving them a serious mental workout – and that your words are being appreciated by a fellow intellect.

Images: iStock/Giphy