What Causes Yawning?

a lack of involuntary breathing… When you get tired all the muscles in your body relax and your breathing slows, so you’re brain triggers a yawn as kind of a kick start.

That, and the lack of oxygen going to your brain.

Yawning causes other people to yawn. ;) They’re contagious you know!

Article: Dog yawns point to capacity for empathy.

Bein’ tiiiiired.

and what they said ^^ :)

boredom

Simple answer. Lack of oxygen. Makes sense? You’re taking in air to make up for it. (:

Scientifically, it’s the body’s way of controlling brain temperature.
According to ancient superstition, if one yawned they needed to cover their mouth because the good spirit could escape and the devil could enter.

For me it’s other people yawning.