You really like that person.
iuricazac/shutterstock 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. 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 that yawns were most contagious between family members, followed by between friends, and least contagious between strangers. When yawns did spread between strangers, it took longer for that second yawn to start than when yawns spread between family and friends.
MORE: 3 Simple Ways To Be A Whole Lot More Empathetic
Your brain needs cooling.
bouybin/shutterstock 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 give us 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.
MORE: 7 Crazy Things You Do In Your Sleep
You have a big brain.
cliparea l custom media/shutterstock 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.
MORE: The Bizarre Ways Dieting Messes With Your Brain
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You could be having a heart attack.
theerapol pongkangsananan/shutterstock 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. 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 to help out.
MORE: 7 Weird Signs You Could Have Heart Trouble Down The Road
Sarah Klein is a Boston-based writer, editor, and personal trainer currently with LIVESTRONG.com, and previously of Health.com, Prevention magazine, and The Huffington Post. She’s the graduate of the Arthur L. Carter Journalism Institute at New York University.
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