Have you ever seen a cloud that looks like an animal? What about that grilled cheese that looked like jesus? Both of those are examples of pareidolia, which occurs when the brain takes meaningless images and turns them into something that means something. I can't tell you the number of times that I was walking around in the dark and thought I saw a man in my house that turned out to be clothes on a chair. More popular examples of pareidolia is the 'Man on the Moon' and the 'Face on Mars' that the textbook talks about. In 1976, the Mars Viking Orbiter took pictures of the surface of Mars and by random chance and the way that light made shadows on the rocks, the picture of rocks on Mars turned into the image of a face. Pareidolia can be so convincing to some people that just this image was enough proof to them that there was intelligent life on Mars. Another example of a large population creating an image out of unintentional stimulus involved the 1954 Canadian dollar. So many people saw an image of the devil in her hair that it was taken out of circulation. The likeness that was used on the bill was taken by a camera and not drawn so there was no devil, but it isn't very hard to see if you look closely.
What examples of pareidolia have you seen in your life?