It is common knowledge that boredom and sleepiness are associated with yawning. Less well known is the correlation between yawning with anxiety and even hunger. There is also research indicating that a yawn is one mechanism with which humans use to cool their brains.
The degree to which others mirror those who are yawning has also been shown to be associated with empathy. We tend to mirror yawning with a significantly greater frequency in those with whom we have greater affection - spouses, children, other family - less so with friends - and it drops off even further with co-workers and acquaintances, etc. Of course, yawning is only one of a vast multitude of behaviors which is mirrored.
This phenomenon exists, at least in part due to the presence and function of what are known as "Mirror Neurons" (Collectively these are known as the Mirror-Neuron-System [MNS]. A better name for these may be "Empathy Neurons"). Moreover there are different sub-types of mirror neurons and much remains to be discovered.
Those individuals with autism spectrum disorder have a relative deficit (and/or hypo-functionality) of one (or more) varieties of mirror neurons. Others - with narcissistic personality disorder and sociopaths have a deficiency or functional problem with another sub-type of mirror neurons. Intriguingly, sociopaths (antisocial personality disorder) and those with narcissistic personalities are much less likely to yawn when they witness other people yawning. This correlation is but one of many nonverbal signals indicative of higher (or lower) empathy quotients. What others can you name?
It will not come as a surprise to many dog lovers (for they are a species noted for high empathy) that not only are yawns are also contagious from dog-to-owner as well as from owner-to-dog.
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