Why do we yawn...I often yawn when browsing the internet after work, or yawn during work. What purpose does it serve? and is it a momentary paralysis of the lower jaw? Also, why is it a subconsious act? I tried to catch one of my yawns in action but no dice. If you wait for one to hit it won't come....and if you try to catch one in motion it quickly disappears once you become too aware of it...why? Always yawned but never knew why.