We yawn when we’re sleepy or bored or if we see someone else yawn. Some people also yawn when they’re anticipating something important and when they’re stressed. Many think we yawn because the brain lacks oxygen, but according www.iflscience.com a new study states, “The thing most of these instances have in common is thermoregulation. Yawning helps cool the brain.”
So why do we yawn when we are tired? Both sleep deprivation and exhaustion are known to increase brain temperature, so while it is true that we yawn to combat lack of sleep, yawns don’t make us “more awake” but instead help keep our brains operating at the right temperature, according to www.independent.co.uk.
Like any computer, the brain has an optimal working temperature and when it becomes too hot yawning helps cool it down, according to science.howstuffworks.com, increasing both the heart rate and blood flow while delivering a big gulp of air to the head, cooling the blood in that area.
Sleep cycles, cortical arousal, and stress are all associated with fluctuations in brain temperature. In previous studies on rats and humans, yawns are preceded by rises in brain temperatures, and they’re followed by equivalent decreases immediately afterwards. If yawning does keep brain temperatures balanced, then to maintain homeostasis, we should only be yawning within an optimal range of temperatures, according to www.iflscience.co.uk.
Previously it’s been thought that yawning served a respiratory function, helping to wake us up with a jolt of oxygen when we were feeling sluggish, but studies have shown that yawning doesn’t actually increase oxygen levels in the body; something that tallies with the simple observation that we don’t yawn when we exercise, a time when we definitely need more oxygen, according to www.independent.co.uk.