Yawning cools a chameleon down.

ChameleonIn a new study the subject is not the controversial hypothesis, which other studies have already refuted, that yawning is prompted by a lack of oxygen in the blood. Rather it is posited that yawning has a heat exchange function. It is held that the inhalation of cool air while yawning regulates the temperature balance in the brain and in that way creates the conditions for optimum alertness and performance.

This hypothesis is supported by a series of tests in which temperature effects have been taken into account. It was found that test persons who were forced to breathe only through the nose yawned much less than those who used their mouth for breathing. The researchers’ explanation is that when we breathe through the nose, the blood in the nose is cooled down well and then circulates through the brain.

Chameleon InfraredIn another test, the test persons were asked to hold a heating / cooling pack to their forehead. Hardly any of the test persons who had the cold pack against their forehead had to yawn during the test period while the other test persons displayed a «normal» yawning behaviour. A similar result was obtained in tests involving changes in room temperature. Conclusion: When it is cooler we stop yawning because it makes no sense for the body from the heat balance point of view.