To yawn serves to cool the head

To yawnis not only an indicator of fatigue or boredom. In fact, the frequency with which we yawn changes according to the station of the year, and that the persons yawn less when the heat outdoors is major that the corporal temperature, which would have justification if the yawn serves in order that the brain regulates his temperature.
The scientists verified that we are more inclined to yawn in winter, in comparison with the summer, when the temperature sets it is equal or superior to the corporal temperature. The high external temperatures do not provide any relief for the warmed brain, whereas when it makes a yawn colder it serves in order that between fresh air and it gets down the temperature of our head.
When we yawn, the stretching of the jaw increases the flow of blood to the brain, and the inhalation of air colder that the organism allows the heat exchange with the environment. " It is a thermal window ", to yawn when it is hot in the exterior might be counter-productive.