Sep 20, 2011
Yawning cools the brain – I’ve discussed yawning and why we yawn several times. Some say we yawn because we’re tired or bored, as some kind of social message, when CO2 levels are high, to get more oxygen into our lungs or maybe to equalise pressure in our heads. Now, a new theory from scientists at Princeton University suggests that yawning simply cools the brain.
Post-doc Andrew Gallup and colleagues have demonstrated that yawning frequency varies with the season and previously that rats yawn less when air temperature exceeds body temperature. Now, writing in the journal Frontiers in Evolutionary Neuroscience, Gallup suggests that the seasonal disparity implies that humans (tested in the desert during cold and hot season) might use yawning to regulate brain temperature. Similar disparity is seen with stretching that might imply stretching too has a thermoregulatory effect.
In their earlier work the team reported that: “Temperature recordings indicate that yawns and stretches occurred during increases in brain temperature, with brain temperatures being restored to baseline following the execution of each of these behaviors,” the researchers explain. “The circulatory changes that accompany yawning and stretching may explain some of the thermal similarities surrounding these events.”
Now, in a paper authored by Andrew Gallup and Omar Tonsi Eldakar, currently in press and entitled “Contagious yawning and seasonal climate variation”, the researchers explain that, “the proportion of pedestrians who yawned in response to seeing pictures of people yawning differed significantly between the two conditions (winter: 45%; summer: 24%).”
They conclude that, “The incidence of yawning in humans is associated with seasonal climate variation,” and that infectious yawns are affected by factors other than the individual’s social characteristics or brain power.
Shoup-Knox ML, Gallup AC, Gallup GG, & McNay EC (2010). Yawning and stretching predict brain temperature changes in rats: support for the thermoregulatory hypothesis. Frontiers in evolutionary neuroscience, 2 PMID: 21031034
Gallup AC and Eldakar OT(2011) Contagious yawning and seasonal
climate variation. Front. Evol. Neurosci. 3:3. DOI: 10.3389/fnevo.2011.00003