Contrast Changes Illusion (IMAGE) American University Caption A freeze frame from the illusion "Grouping by Contrast," which took second prize at the 2011 Best Illusion of the Year Contest. Credit Courtesy Arthur Shapiro (American University), Erica Dixon (American University), and Kai Hamburger (Universität Giessen). Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.