July 08, 2007
Yawning Cools Brain?
Yawning is not contagious for those with cooler brains.
Fifty per cent of people told to breathe normally or through their mouths yawned while watching other people yawn, while none of those told to breathe through their noses yawned. The researchers also found that subjects who held a cold pack to their forehead did not catch yawns from the film, while those who held a warm or room-temperature pack yawned normally (Evolutionary Psychology, vol 5, p 92).
Breathing through your nose cools blood flowing to the brain. Would breathing in through the nose and out through the mouth do a better job of cooling the brain by venting the warmer air from the lungs away from the nose and brain?
Yawning supposedly increases group vigilance. Our hunter ancestors either on stake-out or perhaps manning defense perimeters around camps might have needed to yawn in unison to keep their minds alert to prey or predators. Cooling overheated brains increases their efficiency and hence the yawns.
ALBANY, N.Y. (June 29, 2007) -- The next time you "catch a yawn" from someone across the room, you're not copying their sleepiness, you're participating in an ancient, hardwired ritual that might have evolved to help groups stay alert as a means of detecting danger. That's the conclusion of University at Albany researchers Andrew C. Gallup and Gordon G. Gallup Jr. in a study outlined in the May 2007 issue of Evolutionary Psychology (Volume 5.1., 2007).
The psychologists, who studied yawning in college students, concluded that people do not yawn because they need oxygen, since experiments show that raising or lowering oxygen and carbon dioxide in the blood fails to produce the reaction. Rather, yawning acts as a brain-cooling mechanism. The brain burns up to a third of the calories we consume, and as a consequence generates heat. According to Gallup and Gallup, our brains, not unlike computers, operate more efficiently when cool, and yawning enhances the brain's functioning by increasing blood flow and drawing in cooler air.
Has the need to dissipate heat slowed the evolution of human intelligence just as heat dissipation problems are slowing the rate of advance of modern computer microprocessor speeds?
These results suggest easy practical ways to boost mental performance:
- Turn down office thermostats in summer and winter so that people wear sweaters to keep their torsos warm while keeping their brains cool. Higher mental performance might more than pay back the higher cost of air conditioning in summers. During winters the lower thermostats will save money too.
- A cold pack worn on your forehead might boost your mental performance when you are lagging. But how cold is optimal?
- When you feel like yawning do not suppress it. In fact, when you feel the slightest desire to yawn you might want to take steps to cool your brain.
- Got a cold drink in your hand and your brain lagging? Put the drink up against your forehead.
However, one study showed that warm offices produced fewer errors: http://www.eurekalert.org/pub_releases/2004-10/cuns-slw102004.php
"Chilly workers not only make more errors but cooler temperatures could increase a worker's hourly labor cost by 10 percent, estimates Alan Hedge, professor of design and environmental analysis and director of Cornell's Human Factors and Ergonomics Laboratory.
When the office temperature in a month-long study increased from 68 to 77 degrees Fahrenheit, typing errors fell by 44 percent and typing output jumped 150 percent. Hedge's study was exploring the link between changes in the physical environment and work performance.
"The results of our study also suggest raising the temperature to a more comfortable thermal zone saves employers about $2 per worker, per hour," says Hedge, who presented his findings this summer at the 2004 Eastern Ergonomics Conference and Exposition in New York City. "
Then warm up the office but cool down the brain?
Or are there particular circumstances where the brain overheats? Does it tend to overheat more toward the end of the day?
Or is the brain more likely to overheat if one is doing intellectually more difficult work?
Well, looks like I'm going to have to go review matters, especially those references pertaining to selective cooling of the brain.
The article doesn't jive with me because the obvious function of a yawn, the one that directly correlates to vigilance, has to do with the suspension of the breathing pattern. The human alertness/concentration function requires temporary suspension of breathing. You can prove it to yourselves by going and reading something long and difficult. Note that you will tend to breathe at paragraphs and periods. Yawning, by forcing a full lungful of air and a short expiration, results in a pausal moment. This allows for the initiation of concentration. All consistent with what we know without ever having to invoke thermal changes.
I'm also terribly suspicious of this "cool brain" idea. The brain is essentially a kilo of water at 37 C. It's heat content is immense. It's metabolism and temperature are strictly regulated and remarkably constant, compared to other organs. A yawn lasts a few seconds, can cool at most a thimble of blood a fraction of a degree. Throw in Fourier's Law (k * Surface Area * TempGradient) which confirms everything, so unless the hypothalamus is sensitive to a change of a mere fraction of a degree for a second or so, there's a real problem with the hypothesis.
I grant the actual paper, link easily found in the referred to article, makes a very strong case. My fear however is that the experiment isn't as blind as they think and the stimuli not free of confounding variable. Put a cold pack on my forehead and I will be damn alert just from the skin stimulus. Bye bye yawns! Conversely, give me a hot pack and put me to sleep.
Taking a hint from the above conversation, repeating the experiment in progressively colder room air without pack use, while everyone is toasty in their thorax and legs, would make the case much much stronger.
Cold office lowering productivity, but need to keep your brain cool? Solution: Baldness. ;)