Von, What makes right or left handed people is eyesight.Left handed people are left eye dominant, most of your eye memory and pariphiral vision comes from that eye the right eye is usualy short sighted compared to the left.By stopping vision from the left the body will become more adaptable on the right, or vice versa depending on the side youre dominant. It works better if you stretch regulary. most of the time the function of the opposite side is there to stablize the action of the side which is dominant this can be seen in many sports No in all sports if you observe, hope this helps you to understand it a bit better.