I used to believe that my heart (everyone's heart for that matter) was in the shape of a heart and swung on a chain like a pendulum. I thought a heartbeat was it tick-tocking like a clock. This made me a bit uneasy when I did summersaults or was otherwise upside down.
A childhood belief about general

others believed things like this
- The song called heart of glass mixed me up as a kid. I heard "Heart and ass". — oops
- I used to think that when people had heart attacks someone came and stabbed their heartAnon
- I used to think that if you eat pig heart, you could grow another heart and be twice as healthier. Anon
- I used to believe that the heart at the beginning of the I Love Lucy Show was made of real chocolate.— Krissa
- I thought you always die if you A. get cancer or B. have a heart attack— Nate
- I used to believe an artichoke was an animal and we only ate its heart. — Laura