A spirit doll is more like a statue of St Michael than it is a voodoo doll - it is a representation of a spirit in humanoid form to make it easier to have a relationship with that spirit (for a human being). Only, a spirit doll being handmade, is of course on a totally different level of intimacy for the person compared to looking at something that someone else made a long time ago.

Fashioning a humanoid figure with your own hands is of course one of THE primal art experiences, and one which opens the door to many, many other things, spirit dolls being just one example of that.