I seem to roll around and move a lot when I sleep. Why don't I ever roll right out of bed?
-- Bedbug, La Jolla
A question we've asked here in Rancho de Alice for years. How is it that Pa Alice can balance his bulk on Grandma's dainty couch and not fall gut first onto the coffee table? Unfortunately, he's still a medical mystery, but for normal folks, there might be at least a clue to the answer.
A couple of decades ago, two scientists in Scotland were watching people sleep. They, too, wondered why we don't spin out of the sheets every night, given how messy our beds are in the morning. They watched a series of adults sleep on very wide beds without any blanket or other covering so they had no sense of relative position or movement. Throughout the night the science guys marked every change in body position. Funny thing. Turns out we don't turn. Or spin or roll. Their subjects slept on their left sides for a while, then on their backs, then their right sides, back, left, back, right, and like that. They never turned face down, so they didn't actually roll and never moved too far from where they started, no matter how much they thrashed. When the science guys observed toddlers sleeping, they noted that they will turn onto their faces and will roll; so, they conjectured medically, people somehow learn that face-sleeping constricts breathing, so we don't do it when we grow up. That doesn't really explain why we don�t fall off cots or couches with regularity, though.
I'm not aware that the science guys were laughed out of town over their conclusions. But after careful checking, I couldn't find a sleep researcher aware of any other study. So accept this as a fact-like statement and hope someone else is as curious as you and the Scotsmen.