Yawns are both satisfying and functional. Many mammals, birds, and reptiles employ the yawn
for various uses.
It might increase alertness, reduce nervousness, and regulate body temperature. Some penguin
species use yawning as part of their courtship ritual.
There are many stories and some research that indicate yawning is "contagious."
One animal's yawn can cause another to "sympathetically" yawn. This reflex can
even spread across species. When a person yawns, a dog soon might follow.
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