[ intro ].

Yawning is pretty common for humans, and even for other animals, but we still don’t know for sure why we yawn - or why I yawn when I see you yawn. Yawning often happens when we’re feeling sleepy, bored, or otherwise just not very alert.

But it’s also contagious. You might yawn when you see another person yawn or even when you think about yawning — you might even yawn during this video! It's still not entirely clear what yawning actually does, but research suggests it might have a variety of important functions, and might even help keep us safe.

You see, there was an old idea that stated yawning provided a boost of oxygen for our brains, but that idea doesn’t seem to hold up to the evidence. But there is some indication that your brain cools down when you yawn— like when you take a big inhale, cool air rushes in to cool down the warm blood headed to the brain. Just like the fans that keep your computer from overheating.

But why is yawning so contagious? Some scientists say it’s linked to empathy and the emotional connection with people surrounding you. Research has found that contagious yawning activates similar parts of the brain to other social cues - meaning yawning is an involuntary signal that gets passed through the group.

A study published in January 2021 found that watching the involuntary signal of yawning might actually make your brain more alert. The study tested the group vigilance hypothesis— the idea that when one group member yawns, a possible sign of not being very alert, it signals others to stay vigilant. So the hypothesis here is that yawning becomes contagious so the whole group knows to stay alert!

To test this, researchers ran an experiment with frogs, snakes, and college students. See, previous research has found that humans are really good at spotting snakes - even young children are quicker to notice images of snakes than images of other animals. This might be because snakes can be dangerous.

Most snakes aren’t harmful to humans, but some that are, such as venomous species, can be deadly if you get too close. So, scientists showed 38 participants a series of photos and asked them to either find one frog photo among snakes or one snake among frogs, while also tracking their eyes to see how quickly each person spotted the target photo. Unsurprisingly, the participants in this study spotted snakes faster than frogs.

But here’s the really interesting part— if scientists showed videos of people yawning before the test, participants were even quicker at spotting snakes, and they were more distracted by snake photos while searching for frogs. It seems yawning might kick our brains into alert mode, as contagious yawns spread through a group, they might also make everyone more ready to spot potential danger. So, yawning might be a good way to cool our brains and also signal alertness to others which is why it might be so contagious!

Thanks for watching this episode of SciShow! If you would like to help support the channel, check out Patreon.com/SciShow to learn more. [ outro ].