Most people have seen examples of Contagious Yawning in humans. If one person in a group yawns (or convincingly feigns a yawn) it's often quite hard for others to resist. Current estimates are that 40-60% of human yawns are 'contagious'.
Contagious yawing has also been observed and scientifically documented in many other animals including :
Contagious Yawning can also happen between species. A team at Birkbeck College, University of London, recently performed the first formal research to document Trans Species Yawn Contagion. (man > dog) (reference here)
Another recent study, from the Department of Psychology, Hiram College, US, can be found here (Anim Cogn. 12(6):833-837)
There are theories regarding the possible evolutionary advantages to yawn contagion, for example, that contagious yawning may be part of a neural mechanism involved in empathy. Ref. Cognitive Brain Research Volume 23, Issues 2–3
But a full explanation is currently lacking.
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