What's Yawning For?

When your interlocutor is yawning, that's not because of your infantile and boring conversation. No way, man. American researchers say it's because this way he manages to concentrate better and pay more attention and cool his brain.

A team at the University of Albany found that yawning is not increasing sleepiness, but it has evolved as an ancient, hardwired behavior meant to make us stay alert and detect danger. The team psychologists discovered that people do not yawn for increasing oxygenation, as tests revealed that raising or lowering oxygen and carbon dioxide in the blood does not induce yawning.

It rather seems that yawning cools our brain, which burns more than a quarter of our daily calories, generating heat. Like computer chips, our neurons work better when cool, and yawning enhances this by increasing blood flow and drawing in cooler air.

The psychologists asked the students to watch videotapes of people yawning, assessing the number of contagious yawns. 50 % of those breathing through their mouths yawned at seeing other people yawn, while those breathing through their nose did not yawn at all. In another approach, subjects holding a cold pack to their forehead did not yawn, while those keeping a warm pack or a room temperature pack to their forehead yawned.

It appears that blood vessels in the nasal cavity and face deliver cool blood to the brain, and by breathing through the nose or by cooling the forehead, cooled blood reaches the brain, so that the subjects do not need to yawn.

Recently, multiple sclerosis, a demyelinating condition, has been linked to thermoregulatory dysfunction. Excessive yawning is common in MS, and some diseased experience brief relief after yawning. It also appears that, contrary to the common belief, yawning does not increase sleepiness but rather decreases it.

As yawning takes place when the brain gets heated, the cool blood reaching the brain keeps the optimal levels of mental efficiency. "Therefore, when mental processing slows and someone yawns, the tendency for other people to yawn contagiously might have evolved to promote group vigilance as a means of detecting danger." wrote the researchers.