text: what makes a person yawn after seeing someone else yawn?   it sounds weird, but i personally think that when you see someone yawn, its kind of like a mental thing to think tiredness. so you start thinking tired, and eventually yawn. i'm no expert so don't like hold me to this. =)  i do know that if you hold open you're mouth for a long time, you eventually yawn. i have no clue why i just heard it somewhere. so you might want to ask that in another question haha.