I used to believe that when I breathed in and out, it was my mouth doing the work and not my lungs. And when I saw my chest expanding and retracting, I thought it was weird that it did the opposite of a balloon (when you blow, it expands) so I would try to suck in my gut or push it out and try and reverse the in/out process.
A childhood belief about general

others believed things like this
- My sister told me once that if I sucked too much helium out of a balloon, my lungs would explode.Anon
- I had the weird superstition that if I let all the bathwater run out it'd suck my soul down with it too.— Dan
- When I was about 5, I thought that English was the reverse reading of Turkish.— sel
- I thought everyone only had a set number of breaths before they died.
I breathed slowly for a long time.Anon - I used to believe that aeroplanes could reverse when they are flying. Anon
- I used to think that if you didn't blow your nose and just sniffed the snot up, you head would blow up.Anon