It is also widely referred to as the most popular mysterious action of the human body. The famous expert on yawning Robert R. Provine, a neuroscientist and Professor of Psychology at the University of Maryland, Baltimore County, said, "Yawning may have the dubious distinction of being the least understood, common human behaviour."
In June 2010, there was an International Conference on Yawning in Paris. Many scientists there said yawning need not always be an indication of only boredom. Many researchers are now saying that we might yawn if are stressed or aroused, or it could even be an erotic signal.
One theory is that the temperature of the brain rises because of excitement or stress, and yawning is a natural body mechanism to cool the brain down. But so far there is no way to distinguish which yawn is for what. That could have been quite useful in many situations!
However, there is one takeaway at least. No need to necessarily get offended if someone you are talking to yawns. The signal could be quite contrary!
(This post is a part of the "Blogging from A to Z Challenge April 2018.")