the cricketer David Gower was a famous left-handed batsman. But he's actually right-handed in real life. I don't know how this works. Maybe his cerebral cortex changes sides when he's on grass. Yes, I think it can be taught - right-handedness used to be beaten into lefties (goodness knows why, but the Latin word for left is 'sinister' and I think they might have been seen as suspicious characters). And amputees have to change sides, which I think they do without too much trouble.