Why do people see the Virgin Mary on cheese sandwiches or hear demonic lyrics in "Stairway to Heaven"? Using video, images and music, professional skeptic Michael Shermer explores these and other phenomena, including UFOs and alien sightings. He offers cognitive context: In the absence of sound science, incomplete information can combine with the power of suggestion (helping us hear those Satanic lyrics in Led Zeppelin). In fact, he says, humans tend to convince ourselves to believe: We overvalue the "hits"