I do not express or receive communication on the left side of my face the way I do the right. I think the right side initiates the movement and the left tries somewhat to reflect what the right is doing. When I try to smile my awareness is right side dominated and the left passive and not as complete in the movement. It is the lack of awareness and perception of the left that seems to be reflected in the way I use my left side of the rest of my body. I think it starts with the communication aspect and is reflected by the decreased functional use on the left along with the right side dominance.
Next time my left lower back hurts I will work on my left sided smile. Tongues firmly planted in cheeks.