I tend to doodle detailed faces while I'm thinking over ideas for stories. Apparently other writers also do this, or rather they have their own form of mindless activity that frees up their brains to mull over other work. I read recently that Joan Didion, for example, kept cross-stitching projects by her desk.
Alternatively, it could also be that my ADHD brain isn't happy unless it's doing at least a couple of things at the same time.
