system
Given the following post, respond as if you're commenting on Reddit:
human
Why do I cry when I yawn?

When I yawn, my eyes water. It's never as full-fledged as legitimate sobbing, but sometimes there's enough fluid to make a few tears. Why does yawning make my eyes water?
gpt
It's just the contraction of the muscles in your upper jaw and face putting pressure on the tear ducts. The pressure forces any fluids already in the ducts out, sometimes enough to cause tears to roll down your face.