As a lefty, I still believe it's more natural to use the dominant eating utensil of the fork in our left hands as left handed people, than it is for a righty to use a fork in their left- if anything that's the learned behaviour - dominant left hand utensil is the 'correct' and taught way to eat with knife and fork in polite society.
I remember getting a good laugh out of seeing right handed relatives chastised for using their right hand for a fork at Christmas dinner, one of the few 'normal' things that as a lefty felt totally natural to use a fork in the left.
Think of it this way, as toddlers we don't even use knives, we learn to eat using spoons and plastic forks, mine was always in my left hand. I assume right handed people always in the right as a single utensil, that's one of the first ways you can tell a kid's handedness.
So rightys at some point learned to switch hands for their fork, almost entirely because it's the 'correct' way to eat that their parents were taught to do. Leftys mostly just carry on as nature intended.
If you really want to get some freaky results ask left handed people what hand they use a mouse in a with what button config, EG: I use an ambidextrous mouse in left hand with a right handed mouse button config, leftys using their mouse in the right hand freaks me out, the incredibly rare right handed using mouse left handed even more so.
