New research suggests that yawning cools the brain.
The study, conducted by researchers at University of Vienna and UNY College at Oneonta, USA, explored how ambient temperature affects yawning.
A common belief is that yawning increases oxygen supply to brain. However, few studies have backed this claim.
One theory suggests that brain activity, stress and sleep are all related to changes in brain temperatures. In the current study researchers wanted to know whether changes in ambient temperature were associated with either spontaneous or contagious yawning.
Previous research on yawning focused more on the social aspect. Yawning is linked with empathy and other researchers say that it might have a connection with the need of group vigilance during humans' hunter-gatherer days. The latest study introduces a new factor, brain temperature, in yawn research.
For the study, researchers observed yawning behavior of people in Vienna, Austria, during both winter and summer months and then compared the results with yawning behavior of people in Arizona, USA. Pedestrians were shown images of people yawning and were asked to self-report their yawning behavior, according to a news release.
Researchers found that people in Arizona yawned more in winters than in summers while people in Austria yawned more in summers.
According to the team, people are more likely to yawn at around 20 degree Celsius. They call this range as an optimal thermal zone. People are less likely to yawn when ambient temperatures are high, say 37o C in the summer of Arizona or during the freezing winters of Austria.
The research fits with the social aspect of yawning. Lowering brain temperature could lead to better mental efficiency. The spread of the behavior through the whole group could increase vigilance, researchers said.
The study is published in the journal Physiology & Behavior.