When the anthropologist Eduardo Kohn arrived in a small village deep in the Amazon, people slept largely outdoors in an open thatch house, surrounded by other people. They would wake at night to drink tea, because it was cold, or because of the calls of animals. "Thanks to these continuous disruptions," he writes, "dreams spill into wakefulness and wakefulness into dreams in a way that entangles them both."--from "To Dream in Different Cultures" by T. M. Luhrmann, The New York Times
To my mind, the intriguing question is whether different sleep cultures encourage different patterns of spiritual and supernatural experience. That half-aware, drowsy state is a time when dreams commingle with awareness. People are more likely to have experiences of the impossible then.
Read more from Luhrmann's essay here.