schitzopherics can lucid dream very easily as well. I think in your case you learned from a very young age because usually thats when regular people are most likely to lucid dream in their life. Most kids are able to notice right away without ever really thinking too much about it. It can become a habit for them to where they can lucid dream into adult hood. everyone has probably experienced a lucid dream in their early ages, it just developed as a habit with you, unless your schitzophrenic.