I saw a post on Facebook today saying you have to have a high IQ to read upside down. I don’t think that’s true. I learnt in my childhood. I can’t remember exactly when. I can remember seeing my teachers notes, which was useful and I guess that I practiced doing it later on. I also used to look at text in the mirror, probably after hearing about Leonardo Da Vinci. Strange what you do as a child. Maybe it’s inquisitiveness, maybe pattern recognition?