When I was in the first grade and maybe the second I could do math addition and subtraction backward (from left to right) and do it mostly faster than all the kids carrying from right to left. I often wonder how that would have developed and affected my life if I had never been "corrected". I can still do it a little bit but I never fully developed that skill because it was considered "wrong" by my teachers and I relearned how to do it the traditional way.