When I was young (about 45 years ago) I thought that people saw things by sending out some sort of "eye beams". I was disappointed when I learned the truth because it was just not as cool as my own theory.
A childhood belief about eyes

others believed things like this
- I thought that blackmail meant sending black envelopes to people.Anon
- When I was young I believed that the windmills found in farmers fields were used to keep the cows cool.— Linda
- I used to think that ponies were young horses. I was embarrasingly old when I discovered the truth.— Al's view of the world
- I used to believe that fax machines worked by sending papers down underground tunnels. Anon
- when i was young, i thought all people with the same name would grow up to look the same. — kim
- When I was young I thought people smoked to stay warm.— Phil Stam