Yawning may serve as a natural temperature regulator of the brain, according to U.S. researchers from Princeton. The researchers compared the number of yawns 80 people in the winter time and compared with the number of yawns in the summer.
It is known that yawning "contagious" if someone on the street in winter yawns, almost half will sewnet followed. However, in the summer outdoors number Zinovich decreased by a quarter.
Summer yawn less when the outside temperature exceeds body temperature, this suggests that yawning is a natural cooling mechanism of the brain.
Mechanisms oscitations involved in thermoregulation physiology, despite many theories in the past few decades, very little research uncovers biological function oscitations, and among scientists there is still no consensus on this.
Cooling and thermoregulation of the brain is only a hypothesis that yawning is caused by temperature increase of the brain and the desire to reduce the temperature. When the air temperature is above body temperature sigh will not give relief, because in the summer people yawn frequently. Thus, people tend to yawn in the winter.