You tossed and turned all night. This meeting is dragging on too long. Your kid just yawned across the dinner table and it's unavoidably contagious. Usually when a yawn pops up, you know—or think you know—exactly what it means, case closed.
But the scientific side of things isn't always quite so clear. Long rumored to be a sign of too little oxygen, yawning is actually seen as something totally separate from breathing. (You have to see these 5 things your butt is trying to tell you.) In fact, researchers believe the two are actually controlled by separate mechanisms in the body and brain. And while people certainly report yawning when they're feeling bored or sleepy, there are also those involuntary yawns that seem to have nothing to do with how we're feeling—like athletes who yawn before competitions or Sasha Obama's now rather notorious yawn during her dad's inaugural speech. Heck, you might even be yawning just from reading this. So what do those yawns really mean? Here are a few things they're trying to tell you. (Make 2017 YOUR year with 365 days of simple, effective weight loss and health advice in the Prevention calendar and health planner!)
You really like that person.
Yawns truly are contagious. Experts believe we may have evolved to catch other people's yawns as a way of displaying empathy for one another and deepening those social bonds (be even more caring with these 3 simple ways to be a whole lot more empathetic). So it makes sense that further research discovered that yawns are more contagious the closer you are to someone. In a 2011 study, researchers found yawns were most contagious between family members, followed by friends, and least contagious between strangers. When yawns did spread between strangers, it even took longer for that second yawn to start than when yawns spread between family and friends.
Your brain needs cooling.
In the search for a scientific explanation for why we yawn, the latest theory to arise is that yawning basically gives your brain some fresh air—and cools it down. Further supporting this theory was a 2011 study that found that people yawn more during cooler months and less when the outside temperature is warmer. The cooling of the brain would in turn lead to the extra energy we need in moments when we let out a big yawn—and because sleep deprivation increases brain temp, we may need extra yawns when we're sleepy for additional cooling power. (Check out these 7 crazy things you do in your sleep.)
You have a big brain.
Apparently the bigger your yawn, the bigger your brain, according to a recent report in the journal Biology Letters. The researchers found that mammals that let out big, long yawns (like, oh, humans!) had heavier brains with a higher number of brain cells. Assuming that yawns do indeed cool the brain in order to energize it, bigger brains with more neurons would require more oxygen to wake things up, therefore resulting in bigger yawns, the thinking goes.
You could be having a heart attack.
Or a stroke. Or you might have a tumor. But before you freak: Only excessive yawning, way more yawning than you'd ever expect to produce, is linked to these harrowing health concerns. Heart attacks can stimulate the vagus nerve, which runs from the brain to the abdomen, leading to a reaction that could trigger excessive yawning (you need to know these 7 weird signs you could have heart trouble down the road). Researchers have used MRIs to examine the location of tumors or blockages in the brain, but questions still remain as to how those might disrupt pathways that lead to yawning. People with epilepsy and multiple sclerosis also often report frequent to excessive yawning. These conditions (as well as migraine headaches and even anxiety) have been linked to problems regulating brain temperature—so excessive yawning may be the body's attempt at helping out.