I used to believe that when people would say "pick a number between 1 and 10" you were supposed to pick the number exactly between them. I would of course always pick 5, and be confused when I was wrong.
A childhood belief about counting

others believed things like this
- when i was little i believed that your social security number was the number you were born on the earth — christine
- I used to think that aeroplanes came to your house to pick you up.Anon
- I used to believe your parents PICK your birthday.— Stella
- if you pick your nose, there will be a tune from itAnon
- I used to believe that one day, my younger brother would be older than me and then he'd pick on me!— Andrew
- I used to believe that airplanes would land in your yard and pick you up.— Rachel