"[..] she was also told that we saved electricity if empty sockets were switched off as it stopped electricity "leaking out""
When homes in Britain were converted from gas to electricity it was apparently not unknown for some people to do that.
Much of our learning is built on our general experience. Putting together an exercise bike - it took a few attempts to attach the second pedal before remembering it had a left-handed thread.
People sometimes "correct" me for looking both ways when crossing a one-way street. My reply is: "You know it is a one-way street; I know it is a one way street; someone coming the wrong way obviously doesn't".