Ponca City, We Love You writes "Scientists at University College London have found the link between what we expect to see, and what our brain tells us we actually saw revealing that the context surrounding what we see is all important — sometimes overriding the evidence gathered by our eyes and even causing us to imagine things which aren't really there. A vague background context is more influential and helps us to fill in more blanks than a bright, well-defined context. This may explain why we are prone to 'see' imaginary shapes in the shadows when the light is poor. "Illusionists have been alive to this phenomenon for years," said Professor Zhaoping. "When you see them throw a ball into the air, followed by a second ball, and then a third ball which 'magically' disappears, you wonder how they did it. In truth, there's often no third ball — it's just our brain being deceived by the context, telling us that we really did see three balls launched into the air, one after the other." The original research paper is available on PLOS, the open-access, peer-reviewed journal."