Our minds play tricks on us all the time. Once the information has entered our cognition via our senses, it still has to get processed to be understood. Like any other data, it’s all about context. For interesting examples of optical illusions, please visit http://www.lottolab.org/articles/illusionsoflight.asp. R. Beau Lotto has put together a few interesting examples of mis-processing! Or watch him deliver a talk at TED.