Sleepyheads take note — a UA researcher may have helped discover the cause behind yawning.

Omar Eldakar, a postdoctoral fellow in the UA Center for Insect Science, and Andrew Gallup, a postdoctoral research associate at Princeton University’s Department of Ecology and Evolutionary Biology, have discovered that yawning is actually a mechanism to help cool the brain.

In their report, published this month in the journal Frontiers in Evolutionary Neuroscience, Gallup and Eldakar assert that the connection between yawning frequency and outdoor temperatures is due to the air intake associated with a yawn. Air enters the mouth and circulates throughout the body via the bloodstream, which supplies the brain with oxygen. So if the temperature of the oxygen outside of the brain is cooler than the temperature of the brain itself, then the air outside will actually help cool the brain.

“Our brains are like computers and have optimal operating temperatures, not too hot or not too cold,” Eldakar said. “Yawning helps cool the brain to help maintain these optimal conditions.” According to Eldakar, brain temperature fluctuates depending on the circumstances. Eldakar said that in general, the brain is much warmer during the time just before going to sleep and just after waking up. Eldakar and Gallup hypothesized that this phenomenon has something to do with the relationship between the outside air temperature and the temperature of the brain.

Eldakar and Gallup’s study also found that yawning seems to happen more often in the winter than the summer.

To draw their conclusions, Eldakar and Gallup showed pictures of people yawning to 160 participants in Tucson, half in June 2010 and half in February 2011, and documented how frequently the subjects yawned in response during the summer compared to during the winter.

When it was cooler outside, 45 percent of subjects yawned, but in the summer, only 24 percent of participants were able to yawn. The variance in yawning frequency from season to season is likely because warmer temperatures cannot provide relief for overheated brains.

“It is the temperature of the ambient air that gives a yawn its utility, so if it is too hot outside, yawning can actually increase brain temperature and therefore be counterproductive,” Eldakar said.

The study is the first involving humans to show that the season has an impact on yawning frequency and that people are less likely to yawn when the outdoor heat exceeds body temperature.