Yawning frequencies of people also vary with change in seasonal temperature, a research said.
“The contagious yawning is constrained to an optimal thermal zone or range of ambient temperatures. Yawning subsequently functions to keep the brain temperature balanced and in optimal homeostasis,” explained psychologist Andrew Gallup from State University of New York at Oneonta (SUNY Oneonta).
The researchers hypothesised that yawning should only occur within an optimal range of temperatures – a thermal window.
To test this, Jorg Massen and Kim Dusch of University of Vienna measured contagious yawning frequencies of pedestrians outdoors in Vienna, Austria and during both the winter and summer months.
They compared these results to an identical study conducted earlier in arid climate of Arizona, US.
Pedestrians were asked to view a series of images of people yawning, and then they self-reported on their own yawning behaviour.
Results showed that in Vienna people yawned more in summer than in winter, whereas in Arizona, people yawned more in winter than in summer.
It turned out that it was neither the seasons nor the amount of daylight hours experienced but that contagious yawning was constrained to an optimal thermal zone.
According to Massen, “where yawning functions to cool the brain, yawning is not functional when ambient temperatures are as hot as the body, and may not be necessary or may even have harmful consequences when it is freezing outside”. (ians)