Why Do We Yawn? (And why is it contagious?)
Channel: Brains Applied
Date: 2020-03-21

Hello everyone,

In this video, I'm discussing the very famous phenomenon of yawning. There are many different theories about why people yawn. E.g. The idea that we yawn to get oxygen into our brain. However, there is only one hypothesis that does have many studies that agree: we yawn to cool down our brain.

When we yawn, we constrict and relax our facial muscles. This increases our blood flow towards our face and brain. As our blood is consistently 0.2 degrees colder than our brain, it's a pretty good coolant. While doing so, we also cool our blood through heat exchange with the air. The artery which pumps blood into our brain, the internal carotid artery, is located at the back of our mouth and nose cavity. Yawning thus is ideal to cool down your brain and to remain focused. 

The question remains: why is it contagious? The best explanation for contagious yawning would be an evolutionary one. If you yawn, other people start yawning as well, making everyone more vigilant. For animals as well as for prehistoric people, this would have been ideal. The mechanism behind contagious yawning isn't exactly clear yet. Some studies link it to empathy whilst others think it can be explained through our mirror neurons. Both hypothesis have been tested and in both cases, the studies do show some contradictory results. More research is thus required.

Check out the short video, I hope you like it and of course:
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References:
Gallup, A. C., & Eldakar, O. T. (2013). The thermoregulatory theory of yawning: what we know from over 5 years of research. Frontiers in neuroscience, 6, 188.
Landolt, H. P., Moser, S., Wieser, H. G., Borbély, A. A., & Dijk, D. J. (1995). Intracranial temperature across 24-hour sleep-wake cycles in humans. Neuroreport, 6(6), 913-917.
Massen, J. J., & Gallup, A. C. (2017). Why contagious yawning does not (yet) equate to empathy. Neuroscience & Biobehavioral Reviews, 80, 573-585.
Matthew W. Campbell, & Frans B. M. de Waal (2011). Ingroup-Outgroup Bias in Contagious Yawning by Chimpanzees Supports Link to Empathy PLoS ONE, 6 (4): 10.1371/journal.pone.0018283
Upson, S. (2013). Why is Yawning Contagious? [Video]. Scientific American. Retrieved from https://www.scientificamerican.com/video/why-is-yawning-contagious2013-10-11/