Cause and Effect

I have long believed that the consistent ability to determine causal links is one of the truest benchmarks of intelligience. Simple, and complex, cause and effect problem solving is an important key to success in life.
Tonight while I was getting Ella ready for bed she had a cause and effect breakthrough. As I was changing her diaper she was playing with a clean pillowcase--off the pillow. When she began to put the clean item down by her bottom I quickly put a stop to it. Here's the transcript of the rest of the conversation:
Me: No. No. Please don't put that clean pillowcase on your tush!
Ella: (resisting my demand) Why?
Me: Because I don't want my pillowcase to be dirty!
Ella: (still resisting, but no longer jamming the pillowcase up her &%$) Why?
Me: Because I don't want to put my head on your poop.
Ella: But I'm not putting my poop on your head i'm putting my poop on your pillowcase.
Me: But where do I put my head at night?
Ella: (lightbulbs go off and she makes her SMART face) Um...If I put my poop on your pillowcase and you put your head on your pillowcase then my poop gets on your head (she laughs, and finally puts down the pillowcase for good).
She's brilliant AND I get to sleep easy and poop-free for another night.