A Perspective on 3-D Visual Illusions The leaning tower illusion is one of the simplest visual tricks ever discovered, but it is also one of the most profound contributions to our understanding of depth perception. Three years ago Frederick Kingdom, Ali Yoonessi and Elena Gheorghiu of McGill University noticed that two identical side-by-side images of the Leaning Tower of Pisa appeared to lean at different angles... ADRIANA OLMOS; FROM “THE LEANING TOWER ILLUSION: A NEW ILLUSION OF PERSPECTIVE,” BY F.A.A. KINGDOM, A. YOONESSI, AND E. GHEORGHIU, IN PERCEPTION, VOL. 36; 2007