[These two thoughts may seem disconnected]

Two persons meet on a barge.
One says to the other, “Ya think?”
To which is replied, “What do ya mean?”

…
A Theory of Yawning

People yawn to reset the rhythm of their breathing as it relates to their physical and mental state.

and,
Yawns are “contagious” because when someone sees a person yawn, they have a subconscious desire to match the rhythm of that person who yawned.