From Stephen Mikesell:

Re: What is consciousness? Study aims to settle debate (May 20): The idea to put images near the ceiling in hospital rooms to discover whether people actually had gone out of body in “out of body experiences” was in one of Carl Sagan’s books several decades back, I believe. He advised putting books on a shelves near the ceilings of emergency rooms and then asking people their titles. He was somewhat skeptical and offered an alternative explanation having to do with memory, which perhaps should also be tested.