Hot Headed or Simply Tired?
We’ve all seen it happen, marveled at the constancy, and even blamed the friends around us for our own personal breathing. Does this sound strange? I am talking of course about contagious yawning; this is the phenomenon that seeing someone yawn will cause you to immediately do the same. But why, and for that matter, why even yawn in the first place?
More and more researchers seem to agree that we yawn (actually all vertebrates yawn) as a means of brain thermoregulation. This seems somewhat fantastical at first, but let’s look at the evidence. We have associated yawning for years with being tired. Many of us wake up each morning, yawn and stretch as we get out of bed; we are still tired, right? Or better yet, you’re sitting in the back of your 90 minute lecture, and although you’ve been trying to be more attentive this semester, you can’t help but sit, idly yawning and wishing you were back in your bed for a nap. This theory of thermoregulation actually fits perfectly with us yawning when we are tired.
Thermoregulation has long been attributed to sleep. Sleep is believed to allow our body to properly regulate its temperature, so it should come as no surprise that we yawn—or cool our brains—when we are tired. Without sleep, our bodies have difficulties regulating their temperatures; meaning as we get more tired, our brains could be getting hotter. This simple mechanism of yawning would then allow our bodies to compensate for thermoregulatory failure caused by a lack of sleep.
Further evidence would even allow us to predict the frequency of contagious yawning based upon the ambient temperature. Researchers have found that individuals were more likely to yawn in cooler temperatures (below body temperature) than warmer (above body) temperatures. The longer they were exposed to this ambient temperature, the more they followed this tendency of yawning at the lower temperatures. If you don’t believe this, test it yourself. The next time you are outside in the summer (or in a hot room for a prolonged period of time) think about how many times you yawn and then do the same in colder temperatures. The frequency should be significantly lower in the warm, summer weather, especially the longer you are exposed to it, than in the cold winter.
So if we agree that yawning is the brain’s way of cooling down, why then do we need to yawn contagiously? Is our brain just allowing us to remind others to stay cool? This is doubtful, and researchers cannot actually completely answer this question yet. However, some evidence suggests that contagious yawning serves a function of self-processing and is a part of a neural network that is also involved in empathy.
So the next time you yawn (and I’m sure you did a few times while reading this) simply remember that your brain just needs a quick flux of air to cool off, so it can continue to perform the millions of incredible tasks you make it do every minute of every day.
Really? The Claim: Yawning Cools the Brain – NY Times
Contagious Yawning and Seasonal Climate Variation – Frontiers in Evolutionary Neuroscience
Yawning and Stretching Predict Brain Temperature Changes in Rats: Support for the Thermoregulatory Hypothesis – Frontiers in Evolutionary Neuroscience
Thermoregulation and Sleep – Annals of the New York Academy of Sciences
http://onlinelibrary.wiley.com/doi/10.1002/cphy.cp040259/full
Sleep, Thermoregulation, and Circadian Rhythms – Comprehensive Physiology
