Did you ever have this dream: You have to take an exam that you forgot to prepare for. How about this one: You’re late for a flight because you didn’t arrange transport to the airport.
These fear-filled dreams are quite common, and on Astral Codex Ten, Scott Alexander offers a hypothesis to explain why.
How does this work? You’d have to have some kind of brain cell or whatever on a dedicated loop, checking every few hours to see if there’s a homework assignment you’ve forgotten about. This isn’t just the much easier task of answering “yes” if someone asks you whether you have an assignment. This requires the brain cell to constantly ping memory to see whether there’s something that’s being forgotten.
What if that brain cell is still there? What if, every few hours, it keeps thinking “Oh no, I hope there isn’t a homework assignment I’ve forgotten about, better sift through my memory and see”? And during the day, my brain is functional enough to bar such useless thoughts from my consciousness, but at night, when my guard is down and there’s nothing else to think about, sometimes it gets through? And what if the dreaming brain uses that as the nucleus for a story?
Nehaveigur 