When I was about four or five (early '70s) and telephones had these things on them called "dials"... well, you know how a phone number is written "555-6792"? I thought that since there was no dash ("-") on the dial, that the dash must mean that you had to pause for a couple of seconds. So, when I called my friend I'd dial the first three numbers (this was about 25 years before the whole 10-digit-dialing nonsense), and pause for a few seconds then dial the remaining four digits. Since it worked, I kept doing it.
(later, when I was first introduced to a TouchTone (push-button) phone I was told by the owner that I had to dial slowly -- that if I punched the buttons too quickly the call wouldn't go through. So go figure.)
A childhood belief about telephones

others believed things like this
- I always thought that my relatives were really tiny, and inside my phone when I talked to them on the phone.Anon
- i thought the for sale sign buy owner things meant that u could also buy the owner — brandi
- When I was little i thought that seconds were so fast that you couldn't count them.— Baby
- Until just a few seconds ago, I thought gherkins were beans or something weird like natto...Anon
- Up until 5 seconds ago, I had no idea wat a gherkin was— It's a little cucumber, stupid!
- i used to belive that if my brother pulled a hair out of my arm i would die in 5 seconds — heidi