In Carl Sagan's book, Billions and Billions, he tells a story about a Shaman on some island in the Pacific. The first European explorers had arrived at the shores of his island, but he was unable to see the ships. He knew that something was up because of the unfamiliar way the waves were hitting the shore. Eventually, he followed the waves out, as opposed to in, and was finally able to visualize the tall ships. Sagan's theory was, because the Shaman had never seen tall ships before, his mind was unable to believe what his eyes were seeing.