Drempt I had the unique ability to tell, to the exact percentages, what side - left, right, or middle - people slept on. For example, I'd see a person and say, "Forty two percent left side, twenty eight percent middle, and thirty percent right".
Here's a photo of Mountain Girl, Jerry Garcia's widow when she was in town supporting the Baltimore Symphony Orchestra's renditions of Grateful Dead music. I'm not sure what side she sleeps on.
