Does Yawning Cool Down the Brain?
Australian researchers suggest that yawning might cool an overheated brain. Investigators found that contagious yawning was most prominent in the summer compared to the winter and most likely to occur when the temperature was about 68 degrees Fahrenheit (about 20 degrees Celsius). They suggest that cooling the brain boosts performance, so contagious yawning may be an evolutionary trait meant to improve alertness in groups of people.
Physiology & Behavior, May 2014