Handedness for t'fillin: nature or nurture?
I know that t'fillin are placed on the weaker arm, which for most people is the left, so that the stronger hand is the one doing the binding. I have heard, but don't remember where, that someone who is ambidextrous uses the left as well, since the right isn't weaker and the left is more common.
What about someone who was born left-handed but then was "trained" to be right-handed? While t'fillin doesn't apply to me (and so I ask this just out of curiosity), I'm one of those people -- by nature I am left-handed, but due to some superstitious adults in my early life, I was taught everything right-handed instead. My left arm is stronger, but my right hand is more dextrous. I know several other people like this. (None of them are Jewish men, though, so I can't ask what they do.)
Would someone like this proceed as a right-hander, because that's how that person functions now? Or would that person instead proceed as a left-hander, because that is the way God made that person? (We apply the latter principle in modern gender matters, as I understand it.)