The "reactions" take place in the objects parent space, if the objects aren't parented to anything then the world is their parent. You should parent the slider to something like it's bounding box, then parent the bounding box to the head. That way the sliders parent space is the bounding box and it stops carrying about…
So in 3DS Max I've got my face rig all linked to my controls in the reaction manager and it works fine when it's stationary, however, I'd like for these controls to move with the head rather than stay in the same place. I tried parenting them, but because the reactions are based on the slider's world space position, when I…